Dash Developer Reference

The Developer Reference aims to provide technical details and API information to help you start building Dash-based applications, but it is not a specification. To make the best use of this documentation, you may want to install the current version of Dash Core, either from source or from a pre-compiled executable.

Questions about Dash development are best asked in one of the Dash development communities. Errors or suggestions related to documentation on dash-docs.github.io can be submitted as an issue.

In the following documentation, some strings have been shortened or wrapped: “[…]” indicates extra data was removed, and lines ending in a single backslash “\” are continued below. If you hover your mouse over a paragraph, cross-reference links will be shown in blue. If you hover over a cross-reference link, a brief definition of the term will be displayed in a tooltip.

Not A Specification

The dash-docs.github.io Developer Documentation describes how Dash works to help educate new Dash developers, but it is not a specification—and it never will be.

Dash security depends on consensus. Should your program diverge from consensus, its security is weakened or destroyed. The cause of the divergence doesn’t matter: it could be a bug in your program, it could be an error in this documentation which you implemented as described, or it could be you do everything right but other software on the network behaves unexpectedly as in the case of Bitcoin’s v0.8 chain fork. The specific cause will not matter to the users of your software whose wealth is lost.

The only correct specification of consensus behavior is the actual behavior of programs on the network which maintain consensus. As that behavior is subject to arbitrary inputs in a large variety of unique environments, it cannot ever be fully documented here or anywhere else.

In addition, we also warn you that this documentation has not been extensively reviewed by Dash experts and so likely contains numerous errors. At the bottom of the menu on the left, you will find links that allow you to report an issue or to edit the documentation on GitHub. Please use those links if you find any errors or important missing information.

Block Chain

The following subsections briefly document core block details.

Block Headers

Block headers are serialized in the 80-byte format described below and then hashed as part of the proof-of-work algorithm, making the serialized header format part of the consensus rules.

The hashes are in internal byte order; the other values are all in little-endian order.

An example header in hex:

02000000 ........................... Block version: 2

b6ff0b1b1680a2862a30ca44d346d9e8
910d334beb48ca0c0000000000000000 ... Hash of previous block's header
9d10aa52ee949386ca9385695f04ede2
70dda20810decd12bc9b048aaab31471 ... Merkle root

24d95a54 ........................... Unix time: 1415239972
30c31b18 ........................... Target: 0x1bc330 * 256**(0x18-3)
fe9f0864 ........................... Nonce

Block Versions

• Version 1 was used by Dash for the Genesis Block only.

• Version 2 was introduced with the first block following the Genesis Block (January 2014). As described in BIP34, valid version 2 blocks require a block height parameter in the coinbase.

• Version 3 blocks were introduced in Dash Core 0.11.2 (March 2015) as a soft fork (Block 244,834 was the first version 3 block).

  When the fork reach full enforcement, it required strict DER encoding of all ECDSA signatures in new blocks as described in BIP66. Transactions that do not use strict DER encoding had previously been non-standard since Dash Core 0.8.0.

• Version 4 blocks specified in BIP65 and introduced in Bitcoin Core 0.11.2 (November 2015) as a soft fork became active in December 2015. These blocks now support the new OP_CHECKLOCKTIMEVERIFY opcode described in that BIP.

The mechanism used for the version 2, 3, and 4 upgrades is commonly called IsSuperMajority() after the function added to Dash Core to manage those soft forking changes. See BIP34 for a full description of this method.

As of this writing, a newer method called version bits is being designed to manage future soft forking changes, although it’s not known whether version 4 will be the last soft fork to use the IsSuperMajority() function. Draft BIP9 describes the version bits design as of this writing, although it is still being actively edited and may substantially change while in the draft state.

Merkle Trees

The merkle root is constructed using all the TXIDs of transactions in this block, but first the TXIDs are placed in order as required by the consensus rules:

• The coinbase transaction’s TXID is always placed first.

• Any input within this block can spend an output which also appears in this block (assuming the spend is otherwise valid). However, the TXID corresponding to the output must be placed at some point before the TXID corresponding to the input. This ensures that any program parsing block chain transactions linearly will encounter each output before it is used as an input.

If a block only has a coinbase transaction, the coinbase TXID is used as the merkle root hash.

If a block only has a coinbase transaction and one other transaction, the TXIDs of those two transactions are placed in order, concatenated as 64 raw bytes, and then SHA256(SHA256()) hashed together to form the merkle root.

If a block has three or more transactions, intermediate merkle tree rows are formed. The TXIDs are placed in order and paired, starting with the coinbase transaction’s TXID. Each pair is concatenated together as 64 raw bytes and SHA256(SHA256()) hashed to form a second row of hashes. If there are an odd (non-even) number of TXIDs, the last TXID is concatenated with a copy of itself and hashed. If there are more than two hashes in the second row, the process is repeated to create a third row (and, if necessary, repeated further to create additional rows). Once a row is obtained with only two hashes, those hashes are concatenated and hashed to produce the merkle root.

TXIDs and intermediate hashes are always in internal byte order when they’re concatenated, and the resulting merkle root is also in internal byte order when it’s placed in the block header.

Target nBits

The target threshold is a 256-bit unsigned integer which a header hash must be equal to or below in order for that header to be a valid part of the block chain. However, the header field nBits provides only 32 bits of space, so the target number uses a less precise format called “compact” which works like a base-256 version of scientific notation:

As a base-256 number, nBits can be quickly parsed as bytes the same way you might parse a decimal number in base-10 scientific notation:

Although the target threshold should be an unsigned integer, the original nBits implementation inherits properties from a signed data class, allowing the target threshold to be negative if the high bit of the significand is set. This is useless—the header hash is treated as an unsigned number, so it can never be equal to or lower than a negative target threshold. Dash Core deals with this in two ways:

• When parsing nBits, Dash Core converts a negative target threshold into a target of zero, which the header hash can equal (in theory, at least).

• When creating a value for nBits, Dash Core checks to see if it will produce an nBits which will be interpreted as negative; if so, it divides the significand by 256 and increases the exponent by 1 to produce the same number with a different encoding.

Some examples taken from the Dash Core test cases:

Difficulty 1, the minimum allowed difficulty, is represented on mainnet and the current testnet by the nBits value 0x1e0ffff0. Regtest mode uses a different difficulty 1 value—0x207fffff, the highest possible value below uint32_max which can be encoded; this allows near-instant building of blocks in regtest mode.

Serialized Blocks

Under current consensus rules, a block is not valid unless its serialized size is less than or equal to 1 MB. All fields described below are counted towards the serialized size.

The first transaction in a block must be a coinbase transaction which should collect and spend any transaction fees paid by transactions included in this block.

Until the coin limit (~18 million Dash) is hit, all blocks are entitled to receive a block subsidy of newly created Dash value. The newly created value should be spent in the coinbase transaction.

The block subsidy declines by ~7.1% per year until all Dash is mined. Subsidy calculations are performed by the Dash Core GetBlockSubsidy() function.

Together, the transaction fees and block subsidy are called the block reward. A coinbase transaction is invalid if it tries to spend more value than is available from the block reward.

The block reward is divided into three parts: Miners, Masternodes, and Superblocks.

Transactions

The following subsections briefly document core transaction details.

OpCodes

The opcodes used in the pubkey scripts of standard transactions are:

• Various data pushing opcodes from 0x00 to 0x4e (1–78). These aren’t typically shown in examples, but they must be used to push signatures and public keys onto the stack. See the link below this list for a description.

• OP_TRUE/OP_1 (0x51) and OP_2 through OP_16 (0x52–0x60), which push the values 1 through 16 to the stack.

• OP_CHECKSIG (0xac) consumes a signature and a full public key, and pushes true onto the stack if the transaction data specified by the SIGHASH flag was converted into the signature using the same ECDSA private key that generated the public key. Otherwise, it pushes false onto the stack.

• OP_DUP (0x76) pushes a copy of the topmost stack item on to the stack.

• OP_HASH160 (0xa9) consumes the topmost item on the stack, computes the RIPEMD160(SHA256()) hash of that item, and pushes that hash onto the stack.

• OP_EQUAL (0x87) consumes the top two items on the stack, compares them, and pushes true onto the stack if they are the same, false if not.

• OP_VERIFY (0x69) consumes the topmost item on the stack. If that item is zero (false) it terminates the script in failure.

• OP_EQUALVERIFY (0x88) runs OP_EQUAL and then OP_VERIFY in sequence.

• OP_CHECKMULTISIG (0xae) consumes the value (n) at the top of the stack, consumes that many of the next stack levels (public keys), consumes the value (m) now at the top of the stack, and consumes that many of the next values (signatures) plus one extra value.

  The “one extra value” it consumes is the result of an off-by-one error in the Bitcoin Core implementation. This value is not used, so signature scripts prefix the list of secp256k1 signatures with a single OP_0 (0x00).

  OP_CHECKMULTISIG compares the first signature against each public key until it finds an ECDSA match. Starting with the subsequent public key, it compares the second signature against each remaining public key until it finds an ECDSA match. The process is repeated until all signatures have been checked or not enough public keys remain to produce a successful result.

  Because public keys are not checked again if they fail any signature comparison, signatures must be placed in the signature script using the same order as their corresponding public keys were placed in the pubkey script or redeem script. See the OP_CHECKMULTISIG warning below for more details.

• OP_RETURN (0x6a) terminates the script in failure when executed.

A complete list of opcodes can be found on the Bitcoin Wiki Script Page, with an authoritative list in the opcodetype enum of the Dash Core script header file

Signature script modification warning: Signature scripts are not signed, so anyone can modify them. This means signature scripts should only contain data and data-pushing opcodes which can’t be modified without causing the pubkey script to fail. Placing non-data-pushing opcodes in the signature script currently makes a transaction non-standard, and future consensus rules may forbid such transactions altogether. (Non-data-pushing opcodes are already forbidden in signature scripts when spending a P2SH pubkey script.)

OP_CHECKMULTISIG warning: The multisig verification process described above requires that signatures in the signature script be provided in the same order as their corresponding public keys in the pubkey script or redeem script. For example, the following combined signature and pubkey script will produce the stack and comparisons shown:

OP_0 <A sig> <B sig> OP_2 <A pubkey> <B pubkey> <C pubkey> OP_3

Sig Stack       Pubkey Stack  (Actually a single stack)
---------       ------------
B sig           C pubkey
A sig           B pubkey
OP_0            A pubkey

1. B sig compared to C pubkey (no match)
2. B sig compared to B pubkey (match #1)
3. A sig compared to A pubkey (match #2)

Success: two matches found

But reversing the order of the signatures with everything else the same will fail, as shown below:

OP_0 <B sig> <A sig> OP_2 <A pubkey> <B pubkey> <C pubkey> OP_3

Sig Stack       Pubkey Stack  (Actually a single stack)
---------       ------------
A sig           C pubkey
B sig           B pubkey
OP_0            A pubkey

1. A sig compared to C pubkey (no match)
2. A sig compared to B pubkey (no match)

Failure, aborted: two signature matches required but none found so
                  far, and there's only one pubkey remaining

Address Conversion

The hashes used in P2PKH and P2SH outputs are commonly encoded as Dash addresses. This is the procedure to encode those hashes and decode the addresses.

First, get your hash. For P2PKH, you RIPEMD-160(SHA256()) hash a ECDSA public key derived from your 256-bit ECDSA private key (random data). For P2SH, you RIPEMD-160(SHA256()) hash a redeem script serialized in the format used in raw transactions (described in a following sub-section). Taking the resulting hash:

1. Add an address version byte in front of the hash. The version bytes commonly used by Dash are:

   • 0x4c for P2PKH addresses on the main Dash network (mainnet)

   • 0x8c for P2PKH addresses on the Dash testing network (testnet)

   • 0x10 for P2SH addresses on mainnet

   • 0x13 for P2SH addresses on testnet

2. Create a copy of the version and hash; then hash that twice with SHA256: SHA256(SHA256(version . hash))

3. Extract the first four bytes from the double-hashed copy. These are used as a checksum to ensure the base hash gets transmitted correctly.

4. Append the checksum to the version and hash, and encode it as a base58 string: BASE58(version . hash . checksum)

Dash’s base58 encoding, called Base58Check may not match other implementations. Tier Nolan provided the following example encoding algorithm to the Bitcoin Wiki Base58Check encoding page under the Creative Commons Attribution 3.0 license:

code_string = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
x = convert_bytes_to_big_integer(hash_result)

output_string = ""

while(x > 0)
   {
       (x, remainder) = divide(x, 58)
       output_string.append(code_string[remainder])
   }

repeat(number_of_leading_zero_bytes_in_hash)
   {
   output_string.append(code_string[0]);
   }

output_string.reverse();

Dash’s own code can be traced using the base58 header file.

To convert addresses back into hashes, reverse the base58 encoding, extract the checksum, repeat the steps to create the checksum and compare it against the extracted checksum, and then remove the version byte.

Raw Transaction Format

Dash transactions are broadcast between peers in a serialized byte format, called raw format. It is this form of a transaction which is SHA256(SHA256()) hashed to create the TXID and, ultimately, the merkle root of a block containing the transaction—making the transaction format part of the consensus rules.

Dash Core and many other tools print and accept raw transactions encoded as hex.

All transactions use the version 1 format described below. (Note: transactions in the block chain are allowed to list a higher version number to permit soft forks, but they are treated as version 1 transactions by current software.)

A raw transaction has the following top-level format:

A transaction may have multiple inputs and outputs, so the txIn and txOut structures may recur within a transaction. CompactSize unsigned integers are a form of variable-length integers; they are described in the CompactSize section.

TxIn: A Transaction Input (Non-Coinbase)

Each non-coinbase input spends an outpoint from a previous transaction. (Coinbase inputs are described separately after the example section below.)

Outpoint: The Specific Part Of A Specific Output

Because a single transaction can include multiple outputs, the outpoint structure includes both a TXID and an output index number to refer to specific output.

TxOut: A Transaction Output

Each output spends a certain number of duffs, placing them under control of anyone who can satisfy the provided pubkey script.

Example

The sample raw transaction itemized below is the one created in the Simple Raw Transaction section of the Developer Examples. It spends a previous pay-to-pubkey output by paying to a new pay-to-pubkey-hash (P2PKH) output.

01000000 ................................... Version

01 ......................................... Number of inputs
|
| 7b1eabe0209b1fe794124575ef807057
| c77ada2138ae4fa8d6c4de0398a14f3f ......... Outpoint TXID
| 00000000 ................................. Outpoint index number: 0
|
| 49 ....................................... Bytes in sig. script: 73
| | 48 ..................................... Push 72 bytes as data
| | | 30450221008949f0cb400094ad2b5eb3
| | | 99d59d01c14d73d8fe6e96df1a7150de
| | | b388ab8935022079656090d7f6bac4c9
| | | a94e0aad311a4268e082a725f8aeae05
| | | 73fb12ff866a5f01 ..................... Secp256k1 signature
|
| ffffffff ................................. Sequence number: UINT32_MAX

01 ......................................... Number of outputs
| f0ca052a01000000 ......................... Duffs (49.99990000 Dash)
|
| 19 ....................................... Bytes in pubkey script: 25
| | 76 ..................................... OP_DUP
| | a9 ..................................... OP_HASH160
| | 14 ..................................... Push 20 bytes as data
| | | cbc20a7664f2f69e5355aa427045bc15
| | | e7c6c772 ............................. PubKey hash
| | 88 ..................................... OP_EQUALVERIFY
| | ac ..................................... OP_CHECKSIG

00000000 ................................... locktime: 0 (a block height)

Coinbase Input: The Input Of The First Transaction In A Block

The first transaction in a block, called the coinbase transaction, must have exactly one input, called a coinbase. The coinbase input currently has the following format.

Although the coinbase script is arbitrary data, if it includes the bytes used by any signature-checking operations such as OP_CHECKSIG, those signature checks will be counted as signature operations (sigops) towards the block’s sigop limit. To avoid this, you can prefix all data with the appropriate push operation.

An itemized coinbase transaction:

01000000 .............................. Version

01 .................................... Number of inputs
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ...  Previous outpoint TXID
| ffffffff ............................ Previous outpoint index
|
| 18 .................................. Bytes in coinbase: 24
| |
| | 03 ................................ Bytes in height
| | | b8240b .......................... Height: 730296
| |
| | 03b8240b049d29aa59080400077efa95
| | 0000052f6d70682f .................. Arbitrary data
| 00000000 ............................ Sequence

02 .................................... Output count
| Transaction Output 1
| | f20cbe0a00000000 .................... Duffs (1.80227314 Dash)
| | 1976a9142cd46be3ceeacca983e0fea3
| | b88f26b08a26c29b88ac ................ P2PKH script
|
| Transaction Output 2
| | eb0cbe0a00000000 .................... Duffs (1.80227307 Dash)
| | 1976a914868180414905937a68fadeb0
| | f33e64d102c9591a88ac ................ P2PKH script
|
| 00000000 ............................ Locktime

Note: currently the normal coinbase has 2 outputs (1 for the miner and 1 for the selected masternode). Superblocks (superblock example) have multiple outputs depending on the number of proposals being funded.

CompactSize Unsigned Integers

The raw transaction format and several peer-to-peer network messages use a type of variable-length integer to indicate the number of bytes in a following piece of data.

Dash Core code and this document refers to these variable length integers as compactSize. Many other documents refer to them as var_int or varInt, but this risks conflation with other variable-length integer encodings—such as the CVarInt class used in Dash Core for serializing data to disk. Because it’s used in the transaction format, the format of compactSize unsigned integers is part of the consensus rules.

For numbers from 0 to 252 (0xfc), compactSize unsigned integers look like regular unsigned integers. For other numbers up to 0xffffffffffffffff, a byte is prefixed to the number to indicate its length—but otherwise the numbers look like regular unsigned integers in little-endian order.

For example, the number 515 is encoded as 0xfd0302.

Wallets

Deterministic Wallet Formats

Type 1: Single Chain Wallets

Type 1 deterministic wallets are the simpler of the two, which can create a single series of keys from a single seed. A primary weakness is that if the seed is leaked, all funds are compromised, and wallet sharing is extremely limited.

Type 2: Hierarchical Deterministic (HD) Wallets

For an overview of HD wallets, please see the developer guide section. For details, please see BIP32.

P2P Network

This section describes the Dash P2P network protocol (but it is not a specification). It does not describe the BIP70 payment protocol, the GetBlockTemplate mining protocol, or any network protocol never implemented in an official version of Dash Core.

All peer-to-peer communication occurs entirely over TCP.

Note: unless their description says otherwise, all multi-byte
integers mentioned in this section are transmitted in little-endian order.

Constants And Defaults

The following constants and defaults are taken from Dash Core’s chainparams.cpp source code file.

Note: the testnet start string and nBits above are for testnet3.

Command line parameters can change what port a node listens on (see -help). Start strings are hardcoded constants that appear at the start of all messages sent on the Dash network; they may also appear in data files such as Dash Core’s block database. The Magic Value and nBits displayed above are in big-endian order; they’re sent over the network in little-endian order. The Start String is simply the endian reversed Magic Value.

Dash Core’s chainparams.cpp also includes other constants useful to programs, such as the hash of the genesis blocks for the different networks.

Protocol Versions

The table below lists some notable versions of the P2P network protocol, with the most recent versions listed first. (If you know of a protocol version that implemented a major change but which is not listed here, please open an issue.)

As of Dash Core 0.12.2.0, the most recent protocol version is 70208.

Historical Bitcoin protocol versions for reference shown below since Dash is a fork of Bitcoin Core.

Message Headers

All messages in the network protocol use the same container format, which provides a required multi-field message header and an optional payload. The message header format is:

The following example is an annotated hex dump of a mainnet message header from a verack message which has no payload.

bf0c6bbd ................... Start string: Mainnet
76657261636b000000000000 ... Command name: verack + null padding
00000000 ................... Byte count: 0
5df6e0e2 ................... Checksum: SHA256(SHA256(<empty>))

Data Messages

The following network messages all request or provide data related to transactions and blocks.

Many of the data messages use inventories as unique identifiers for transactions and blocks. Inventories have a simple 36-byte structure:

The currently-available type identifiers are:

Type identifier zero and type identifiers greater than nineteen are reserved for future implementations. Dash Core ignores all inventories with one of these unknown types.

Block

The block message transmits a single serialized block in the format described in the serialized blocks section. See that section for an example hexdump. It can be sent for two different reasons:

1. GetData Response: Nodes will always send it in response to a getdata message that requests the block with an inventory type of MSG_BLOCK (provided the node has that block available for relay).

2. Unsolicited: Some miners will send unsolicited block messages broadcasting their newly-mined blocks to all of their peers. Many mining pools do the same thing, although some may be misconfigured to send the block from multiple nodes, possibly sending the same block to some peers more than once.

GetBlocks

The getblocks message requests an inv message that provides block header hashes starting from a particular point in the block chain. It allows a peer which has been disconnected or started for the first time to get the data it needs to request the blocks it hasn’t seen.

Peers which have been disconnected may have stale blocks in their locally-stored block chain, so the getblocks message allows the requesting peer to provide the receiving peer with multiple header hashes at various heights on their local chain. This allows the receiving peer to find, within that list, the last header hash they had in common and reply with all subsequent header hashes.

Note: the receiving peer itself may respond with an inv message containing header hashes of stale blocks. It is up to the requesting peer to poll all of its peers to find the best block chain.

If the receiving peer does not find a common header hash within the list, it will assume the last common block was the genesis block (block zero), so it will reply with in inv message containing header hashes starting with block one (the first block after the genesis block).

The following annotated hexdump shows a getblocks message. (The message header has been omitted.)

71110100 ........................... Protocol version: 70001
02 ................................. Hash count: 2

d39f608a7775b537729884d4e6633bb2
105e55a16a14d31b0000000000000000 ... Hash #1

5c3e6403d40837110a2e8afb602b1c01
714bda7ce23bea0a0000000000000000 ... Hash #2

00000000000000000000000000000000
00000000000000000000000000000000 ... Stop hash

GetData

The getdata message requests one or more data objects from another node. The objects are requested by an inventory, which the requesting node typically previously received by way of an inv message.

The response to a getdata message can be a tx message, block message, merkleblock message, ix message, txlvote message, mnw message, mnb message, mnp message, dstx message, govobj message, govobjvote message, mnv message, or notfound message.

This message cannot be used to request arbitrary data, such as historic transactions no longer in the memory pool or relay set. Full nodes may not even be able to provide older blocks if they’ve pruned old transactions from their block database. For this reason, the getdata message should usually only be used to request data from a node which previously advertised it had that data by sending an inv message.

The format and maximum size limitations of the getdata message are identical to the inv message; only the message header differs.

GetHeaders

Added in protocol version 70077.

The getheaders message requests a headers message that provides block headers starting from a particular point in the block chain. It allows a peer which has been disconnected or started for the first time to get the headers it hasn’t seen yet.

The getheaders message is nearly identical to the getblocks message, with one minor difference: the inv reply to the getblocks message will include no more than 500 block header hashes; the headers reply to the getheaders message will include as many as 2,000 block headers.

Headers

Added in protocol version 31800 (of Bitcoin).

The headers message sends block headers to a node which previously requested certain headers with a getheaders message. A headers message can be empty.

The following annotated hexdump shows a headers message. (The message header has been omitted.)

01 ................................. Header count: 1

02000000 ........................... Block version: 2
b6ff0b1b1680a2862a30ca44d346d9e8
910d334beb48ca0c0000000000000000 ... Hash of previous block's header
9d10aa52ee949386ca9385695f04ede2
70dda20810decd12bc9b048aaab31471 ... Merkle root
24d95a54 ........................... Unix time: 1415239972
30c31b18 ........................... Target (bits)
fe9f0864 ........................... Nonce

00 ................................. Transaction count (0x00)

Inv

The inv message (inventory message) transmits one or more inventories of objects known to the transmitting peer. It can be sent unsolicited to announce new transactions or blocks, or it can be sent in reply to a getblocks message or mempool message.

The receiving peer can compare the inventories from an inv message against the inventories it has already seen, and then use a follow-up message to request unseen objects.

The following annotated hexdump shows an inv message with two inventory entries. (The message header has been omitted.)

02 ................................. Count: 2

0f000000 ........................... Type: MSG_MASTERNODE_PING
dd6cc6c11211793b239c2e311f1496e2
2281b200b35233eaae465d2aa3c9d537 ... Hash (mnp)

05000000 ........................... Type: MSG_TXLOCK_VOTE
afc5b2f418f8c06c477a7d071240f5ee
ab17057f9ce4b50c2aef4fadf3729a2e ... Hash (txlvote)

MemPool

Added in protocol version 60002 (of Bitcoin).

The mempool message requests the TXIDs of transactions that the receiving node has verified as valid but which have not yet appeared in a block. That is, transactions which are in the receiving node’s memory pool. The response to the mempool message is one or more inv messages containing the TXIDs in the usual inventory format.

Sending the mempool message is mostly useful when a program first connects to the network. Full nodes can use it to quickly gather most or all of the unconfirmed transactions available on the network; this is especially useful for miners trying to gather transactions for their transaction fees. SPV clients can set a filter before sending a mempool to only receive transactions that match that filter; this allows a recently-started client to get most or all unconfirmed transactions related to its wallet.

The inv response to the mempool message is, at best, one node’s view of the network—not a complete list of unconfirmed transactions on the network. Here are some additional reasons the list might not be complete:

• Before Bitcoin Core 0.9.0, the response to the mempool message was only one inv message. An inv message is limited to 50,000 inventories, so a node with a memory pool larger than 50,000 entries would not send everything. Later versions of Bitcoin Core send as many inv messages as needed to reference its complete memory pool.

• The mempool message is not currently fully compatible with the filterload message’s BLOOM_UPDATE_ALL and BLOOM_UPDATE_P2PUBKEY_ONLY flags. Mempool transactions are not sorted like in-block transactions, so a transaction (tx2) spending an output can appear before the transaction (tx1) containing that output, which means the automatic filter update mechanism won’t operate until the second-appearing transaction (tx1) is seen—missing the first-appearing transaction (tx2). It has been proposed in Bitcoin Core issue #2381 that the transactions should be sorted before being processed by the filter.

There is no payload in a mempool message. See the message header section for an example of a message without a payload.

MerkleBlock

Added in protocol version 70001 as described by BIP37.

The merkleblock message is a reply to a getdata message which requested a block using the inventory type MSG_MERKLEBLOCK. It is only part of the reply: if any matching transactions are found, they will be sent separately as tx messages.

If a filter has been previously set with the filterload message, the merkleblock message will contain the TXIDs of any transactions in the requested block that matched the filter, as well as any parts of the block’s merkle tree necessary to connect those transactions to the block header’s merkle root. The message also contains a complete copy of the block header to allow the client to hash it and confirm its proof of work.

The annotated hexdump below shows a merkleblock message which corresponds to the examples below. (The message header has been omitted.)

01000000 ........................... Block version: 1
82bb869cf3a793432a66e826e05a6fc3
7469f8efb7421dc88067010000000000 ... Hash of previous block's header
7f16c5962e8bd963659c793ce370d95f
093bc7e367117b3c30c1f8fdd0d97287 ... Merkle root
76381b4d ........................... Time: 1293629558
4c86041b ........................... nBits: 0x04864c * 256**(0x1b-3)
554b8529 ........................... Nonce

07000000 ........................... Transaction count: 7
04 ................................. Hash count: 4

3612262624047ee87660be1a707519a4
43b1c1ce3d248cbfc6c15870f6c5daa2 ... Hash #1
019f5b01d4195ecbc9398fbf3c3b1fa9
bb3183301d7a1fb3bd174fcfa40a2b65 ... Hash #2
41ed70551dd7e841883ab8f0b16bf041
76b7d1480e4f0af9f3d4c3595768d068 ... Hash #3
20d2a7bc994987302e5b1ac80fc425fe
25f8b63169ea78e68fbaaefa59379bbf ... Hash #4

01 ................................. Flag bytes: 1
1d ................................. Flags: 1 0 1 1 1 0 0 0

Note: when fully decoded, the above merkleblock message provided the TXID for a single transaction that matched the filter. In the network traffic dump this output was taken from, the full transaction belonging to that TXID was sent immediately after the merkleblock message as a tx message.

Parsing A MerkleBlock Message

As seen in the annotated hexdump above, the merkleblock message provides three special data types: a transaction count, a list of hashes, and a list of one-bit flags.

You can use the transaction count to construct an empty merkle tree. We’ll call each entry in the tree a node; on the bottom are TXID nodes—the hashes for these nodes are TXIDs; the remaining nodes (including the merkle root) are non-TXID nodes—they may actually have the same hash as a TXID, but we treat them differently.

Keep the hashes and flags in the order they appear in the merkleblock message. When we say “next flag” or “next hash”, we mean the next flag or hash on the list, even if it’s the first one we’ve used so far.

Start with the merkle root node and the first flag. The table below describes how to evaluate a flag based on whether the node being processed is a TXID node or a non-TXID node. Once you apply a flag to a node, never apply another flag to that same node or reuse that same flag again.

Any time you begin processing a node for the first time, evaluate the next flag. Never use a flag at any other time.

When processing a child node, you may need to process its children (the grandchildren of the original node) or further-descended nodes before returning to the parent node. This is expected—keep processing depth first until you reach a TXID node or a non-TXID node with a flag of 0.

After you process a TXID node or a non-TXID node with a flag of 0, stop processing flags and begin to ascend the tree. As you ascend, compute the hash of any nodes for which you now have both child hashes or for which you now have the sole child hash. See the merkle tree section for hashing instructions. If you reach a node where only the left hash is known, descend into its right child (if present) and further descendants as necessary.

However, if you find a node whose left and right children both have the same hash, fail. This is related to CVE-2012-2459.

Continue descending and ascending until you have enough information to obtain the hash of the merkle root node. If you run out of flags or hashes before that condition is reached, fail. Then perform the following checks (order doesn’t matter):

• Fail if there are unused hashes in the hashes list.

• Fail if there are unused flag bits—except for the minimum number of bits necessary to pad up to the next full byte.

• Fail if the hash of the merkle root node is not identical to the merkle root in the block header.

• Fail if the block header is invalid. Remember to ensure that the hash of the header is less than or equal to the target threshold encoded by the nBits header field. Your program should also, of course, attempt to ensure the header belongs to the best block chain and that the user knows how many confirmations this block has.

For a detailed example of parsing a merkleblock message, please see the corresponding merkle block examples section.

Creating A MerkleBlock Message

It’s easier to understand how to create a merkleblock message after you understand how to parse an already-created message, so we recommend you read the parsing section above first.

Create a complete merkle tree with TXIDs on the bottom row and all the other hashes calculated up to the merkle root on the top row. For each transaction that matches the filter, track its TXID node and all of its ancestor nodes.

Start processing the tree with the merkle root node. The table below describes how to process both TXID nodes and non-TXID nodes based on whether the node is a match, a match ancestor, or neither a match nor a match ancestor.

Any time you begin processing a node for the first time, a flag should be appended to the flag list. Never put a flag on the list at any other time, except when processing is complete to pad out the flag list to a byte boundary.

When processing a child node, you may need to process its children (the grandchildren of the original node) or further-descended nodes before returning to the parent node. This is expected—keep processing depth first until you reach a TXID node or a node which is neither a TXID nor a match ancestor.

After you process a TXID node or a node which is neither a TXID nor a match ancestor, stop processing and begin to ascend the tree until you find a node with a right child you haven’t processed yet. Descend into that right child and process it.

After you fully process the merkle root node according to the instructions in the table above, processing is complete. Pad your flag list to a byte boundary and construct the merkleblock message using the template near the beginning of this subsection.

NotFound

Added in protocol version 70001.

The notfound message is a reply to a getdata message which requested an object the receiving node does not have available for relay. (Nodes are not expected to relay historic transactions which are no longer in the memory pool or relay set. Nodes may also have pruned spent transactions from older blocks, making them unable to send those blocks.)

The format and maximum size limitations of the notfound message are identical to the inv message; only the message header differs.

Tx

The tx message transmits a single transaction in the raw transaction format. It can be sent in a variety of situations;

• Transaction Response: Dash Core will send it in response to a getdata message that requests the transaction with an inventory type of MSG_TX.

• MerkleBlock Response: Dash Core will send it in response to a getdata message that requests a merkle block with an inventory type of MSG_MERKLEBLOCK. (This is in addition to sending a merkleblock message.) Each tx message in this case provides a matched transaction from that block.

For an example hexdump of the raw transaction format, see the raw transaction section.

Control Messages

The following network messages all help control the connection between two peers or allow them to advise each other about the rest of the network.

Note that almost none of the control messages are authenticated in any way, meaning they can contain incorrect or intentionally harmful information. In addition, this section does not yet cover P2P protocol operation over the Tor network; if you would like to contribute information about Tor, please open an issue.

Addr

The addr (IP address) message relays connection information for peers on the network. Each peer which wants to accept incoming connections creates an addr message providing its connection information and then sends that message to its peers unsolicited. Some of its peers send that information to their peers (also unsolicited), some of which further distribute it, allowing decentralized peer discovery for any program already on the network.

An addr message may also be sent in response to a getaddr message.

Each encapsulated network IP address currently uses the following structure:

The following annotated hexdump shows part of an addr message. (The message header has been omitted and the actual IP address has been replaced with a RFC5737 reserved IP address.)

fde803 ............................. Address count: 1000

d91f4854 ........................... Epoch time: 1414012889
0100000000000000 ................... Service bits: 01 (network node)
00000000000000000000ffffc0000233 ... IP Address: ::ffff:192.0.2.51
208d ............................... Port: 8333

[...] .............................. (999 more addresses omitted)

Alert

Added in protocol version 311. Removed by Bitcoin in protocol version 70013, but retained by Dash.

The alert message warns nodes of problems that may affect them or the rest of the network. Each alert message is signed using a key controlled by respected community members, mostly Dash Core developers.

To ensure all nodes can validate and forward alert messages, encapsulation is used. Developers create an alert using the data structure appropriate for the versions of the software they want to notify; then they serialize that data and sign it. The serialized data and its signature make up the outer alert message—allowing nodes which don’t understand the data structure to validate the signature and relay the alert to nodes which do understand it. The nodes which actually need the message can decode the serialized data to access the inner alert message.

The outer alert message has four fields:

Although designed to be easily upgraded, the format of the inner serialized alert has not changed since the alert message was first introduced in protocol version 311.

The annotated hexdump below shows an alert message. (The message header has been omitted.)

73 ................................. Bytes in encapsulated alert: 115
01000000 ........................... Version: 1
3766404f00000000 ................... RelayUntil: 1329620535
b305434f00000000 ................... Expiration: 1330917376

f2030000 ........................... ID: 1010
f1030000 ........................... Cancel: 1009
00 ................................. setCancel count: 0

10270000 ........................... MinVer: 10000
48ee0000 ........................... MaxVer: 61000
00 ................................. setUser_agent bytes: 0
64000000 ........................... Priority: 100

00 ................................. Bytes In Comment String: 0
46 ................................. Bytes in StatusBar String: 70
53656520626974636f696e2e6f72672f
666562323020696620796f7520686176
652074726f75626c6520636f6e6e6563
74696e67206166746572203230204665
627275617279 ....................... Status Bar String: "See [...]"
00 ................................. Bytes In Reserved String: 0

47 ................................. Bytes in signature: 71
30450221008389df45f0703f39ec8c1c
c42c13810ffcae14995bb648340219e3
53b63b53eb022009ec65e1c1aaeec1fd
334c6b684bde2b3f573060d5b70c3a46
723326e4e8a4f1 ..................... Signature

Alert key compromise: Dash Core’s source code defines a particular set of alert parameters that can be used to notify users that the alert signing key has been compromised and that they should upgrade to get a new alert public key. Once a signed alert containing those parameters has been received, no other alerts can cancel or override it. See the ProcessAlert() function in the Dash Core alert.cpp source code for the parameters of this message.

FilterAdd

Added in protocol version 70001 as described by BIP37.

The filteradd message tells the receiving peer to add a single element to a previously-set bloom filter, such as a new public key. The element is sent directly to the receiving peer; the peer then uses the parameters set in the filterload message to add the element to the bloom filter.

Because the element is sent directly to the receiving peer, there is no obfuscation of the element and none of the plausible-deniability privacy provided by the bloom filter. Clients that want to maintain greater privacy should recalculate the bloom filter themselves and send a new filterload message with the recalculated bloom filter.

Note: a filteradd message will not be accepted unless a filter was previously set with the filterload message.

The annotated hexdump below shows a filteradd message adding a TXID. (The message header has been omitted.) This TXID appears in the same block used for the example hexdump in the merkleblock message; if that merkleblock message is re-sent after sending this filteradd message, six hashes are returned instead of four.

20 ................................. Element bytes: 32
fdacf9b3eb077412e7a968d2e4f11b9a
9dee312d666187ed77ee7d26af16cb0b ... Element (A TXID)

FilterClear

Added in protocol version 70001 as described by BIP37.

The filterclear message tells the receiving peer to remove a previously-set bloom filter. This also undoes the effect of setting the relay field in the version message to 0, allowing unfiltered access to inv messages announcing new transactions.

Dash Core does not require a filterclear message before a replacement filter is loaded with filterload. It also doesn’t require a filterload message before a filterclear message.

There is no payload in a filterclear message. See the message header section for an example of a message without a payload.

FilterLoad

Added in protocol version 70001 as described by BIP37.

The filterload message tells the receiving peer to filter all relayed transactions and requested merkle blocks through the provided filter. This allows clients to receive transactions relevant to their wallet plus a configurable rate of false positive transactions which can provide plausible-deniability privacy.

The annotated hexdump below shows a filterload message. (The message header has been omitted.) For an example of how this payload was created, see the filterload example.

02 ......... Filter bytes: 2
b50f ....... Filter: 1010 1101 1111 0000
0b000000 ... nHashFuncs: 11
00000000 ... nTweak: 0/none
00 ......... nFlags: BLOOM_UPDATE_NONE

Initializing A Bloom Filter

Filters have two core parameters: the size of the bit field and the number of hash functions to run against each data element. The following formulas from BIP37 will allow you to automatically select appropriate values based on the number of elements you plan to insert into the filter (n) and the false positive rate (p) you desire to maintain plausible deniability.

• Size of the bit field in bytes (nFilterBytes), up to a maximum of 36,000: (-1 / log(2)**2 * n * log(p)) / 8

• Hash functions to use (nHashFuncs), up to a maximum of 50: nFilterBytes * 8 / n * log(2)

Note that the filter matches parts of transactions (transaction elements), so the false positive rate is relative to the number of elements checked—not the number of transactions checked. Each normal transaction has a minimum of four matchable elements (described in the comparison subsection below), so a filter with a false-positive rate of 1 percent will match about 4 percent of all transactions at a minimum.

According to BIP37, the formulas and limits described above provide support for bloom filters containing 20,000 items with a false positive rate of less than 0.1 percent or 10,000 items with a false positive rate of less than 0.0001 percent.

Once the size of the bit field is known, the bit field should be initialized as all zeroes.

Populating A Bloom Filter

The bloom filter is populated using between 1 and 50 unique hash functions (the number specified per filter by the nHashFuncs field). Instead of using up to 50 different hash function implementations, a single implementation is used with a unique seed value for each function.

The seed is nHashNum * 0xfba4c795 + nTweak as a uint32_t, where the values are:

• nHashNum is the sequence number for this hash function, starting at 0 for the first hash iteration and increasing up to the value of the nHashFuncs field (minus one) for the last hash iteration.

• 0xfba4c795 is a constant optimized to create large differences in the seed for different values of nHashNum.

• nTweak is a per-filter constant set by the client to require the use of an arbitrary set of hash functions.

If the seed resulting from the formula above is larger than four bytes, it must be truncated to its four most significant bytes (for example, 0x8967452301 & 0xffffffff → 0x67452301).

The actual hash function implementation used is the 32-bit Murmur3 hash function.

Warning: the Murmur3 hash function has separate 32-bit and 64-bit versions that produce different results for the same input. Only the 32-bit Murmur3 version is used with Dash bloom filters.

The data to be hashed can be any transaction element which the bloom filter can match. See the next subsection for the list of transaction elements checked against the filter. The largest element which can be matched is a script data push of 520 bytes, so the data should never exceed 520 bytes.

The example below from Dash Core bloom.cpp combines all the steps above to create the hash function template. The seed is the first parameter; the data to be hashed is the second parameter. The result is a uint32_t modulo the size of the bit field in bits.

MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8)

Each data element to be added to the filter is hashed by nHashFuncs number of hash functions. Each time a hash function is run, the result will be the index number (nIndex) of a bit in the bit field. That bit must be set to 1. For example if the filter bit field was 00000000 and the result is 5, the revised filter bit field is 00000100 (the first bit is bit 0).

It is expected that sometimes the same index number will be returned more than once when populating the bit field; this does not affect the algorithm—after a bit is set to 1, it is never changed back to 0.

After all data elements have been added to the filter, each set of eight bits is converted into a little-endian byte. These bytes are the value of the filter field.

Comparing Transaction Elements To A Bloom Filter

To compare an arbitrary data element against the bloom filter, it is hashed using the same parameters used to create the bloom filter. Specifically, it is hashed nHashFuncs times, each time using the same nTweak provided in the filter, and the resulting output is modulo the size of the bit field provided in the filter field. After each hash is performed, the filter is checked to see if the bit at that indexed location is set. For example if the result of a hash is 5 and the filter is 01001110, the bit is considered set.

If the result of every hash points to a set bit, the filter matches. If any of the results points to an unset bit, the filter does not match.

The following transaction elements are compared against bloom filters. All elements will be hashed in the byte order used in blocks (for example, TXIDs will be in internal byte order).

• TXIDs: the transaction’s SHA256(SHA256()) hash.

• Outpoints: each 36-byte outpoint used this transaction’s input section is individually compared to the filter.

• Signature Script Data: each element pushed onto the stack by a data-pushing opcode in a signature script from this transaction is individually compared to the filter. This includes data elements present in P2SH redeem scripts when they are being spent.

• PubKey Script Data: each element pushed onto the the stack by a data-pushing opcode in any pubkey script from this transaction is individually compared to the filter. (If a pubkey script element matches the filter, the filter will be immediately updated if the BLOOM_UPDATE_ALL flag was set; if the pubkey script is in the P2PKH format and matches the filter, the filter will be immediately updated if the BLOOM_UPDATE_P2PUBKEY_ONLY flag was set. See the subsection below for details.)

The following annotated hexdump of a transaction is from the raw transaction format section; the elements which would be checked by the filter are emphasized in bold. Note that this transaction’s TXID (01000000017b1eab[...]) would also be checked, and that the outpoint TXID and index number below would be checked as a single 36-byte element.

01000000 ................................... Version

01 ......................................... Number of inputs
|
| 7b1eabe0209b1fe794124575ef807057
| c77ada2138ae4fa8d6c4de0398a14f3f ......... Outpoint TXID
| 00000000 ................................. Outpoint index number
|
| 49 ....................................... Bytes in sig. script: 73
| | 48 ..................................... Push 72 bytes as data
| | | 30450221008949f0cb400094ad2b5eb3
| | | 99d59d01c14d73d8fe6e96df1a7150de
| | | b388ab8935022079656090d7f6bac4c9
| | | a94e0aad311a4268e082a725f8aeae05
| | | 73fb12ff866a5f01 ..................... Secp256k1 signature
|
| ffffffff ................................. Sequence number: UINT32_MAX

01 ......................................... Number of outputs
| f0ca052a01000000 ......................... Satoshis (49.99990000 BTC)
|
| 19 ....................................... Bytes in pubkey script: 25
| | 76 ..................................... OP_DUP
| | a9 ..................................... OP_HASH160
| | 14 ..................................... Push 20 bytes as data
| | | cbc20a7664f2f69e5355aa427045bc15
| | | e7c6c772 ............................. PubKey hash
| | 88 ..................................... OP_EQUALVERIFY
| | ac ..................................... OP_CHECKSIG

00000000 ................................... locktime: 0 (a block height)

Updating A Bloom Filter

Clients will often want to track inputs that spend outputs (outpoints) relevant to their wallet, so the filterload field nFlags can be set to allow the filtering node to update the filter when a match is found. When the filtering node sees a pubkey script that pays a pubkey, address, or other data element matching the filter, the filtering node immediately updates the filter with the outpoint corresponding to that pubkey script.

If an input later spends that outpoint, the filter will match it, allowing the filtering node to tell the client that one of its transaction outputs has been spent.

The nFlags field has three allowed values:

In addition, because the filter size stays the same even though additional elements are being added to it, the false positive rate increases. Each false positive can result in another element being added to the filter, creating a feedback loop that can (after a certain point) make the filter useless. For this reason, clients using automatic filter updates need to monitor the actual false positive rate and send a new filter when the rate gets too high.

GetAddr

The getaddr message requests an addr message from the receiving node, preferably one with lots of IP addresses of other receiving nodes. The transmitting node can use those IP addresses to quickly update its database of available nodes rather than waiting for unsolicited addr messages to arrive over time.

There is no payload in a getaddr message. See the message header section for an example of a message without a payload.

GetSporks

The getsporks message requests spork messages from the receiving node.

There is no payload in a getsporks message. See the message header section for an example of a message without a payload.

Ping

The ping message helps confirm that the receiving peer is still connected. If a TCP/IP error is encountered when sending the ping message (such as a connection timeout), the transmitting node can assume that the receiving node is disconnected. The response to a ping message is the pong message.

Before protocol version 60000, the ping message had no payload. As of protocol version 60001 and all later versions, the message includes a single field, the nonce.

The annotated hexdump below shows a ping message. (The message header has been omitted.)

0094102111e2af4d ... Nonce

Pong

Added in protocol version 60001 as described by BIP31.

The pong message replies to a ping message, proving to the pinging node that the ponging node is still alive. Dash Core will, by default, disconnect from any clients which have not responded to a ping message within 20 minutes.

To allow nodes to keep track of latency, the pong message sends back the same nonce received in the ping message it is replying to.

The format of the pong message is identical to the ping message; only the message header differs.

Reject

Added in protocol version 70002 as described by BIP61.

The reject message informs the receiving node that one of its previous messages has been rejected.

The following table lists message reject codes. Codes are tied to the type of message they reply to; for example there is a 0x10 reject code for transactions and a 0x10 reject code for blocks.

Reject Codes

The annotated hexdump below shows a reject message. (The message header has been omitted.)

02 ................................. Number of bytes in message: 2
7478 ............................... Type of message rejected: tx
12 ................................. Reject code: 0x12 (duplicate)
15 ................................. Number of bytes in reason: 21
6261642d74786e732d696e707574732d
7370656e74 ......................... Reason: bad-txns-inputs-spent
394715fcab51093be7bfca5a31005972
947baf86a31017939575fb2354222821 ... TXID

SendHeaders

The sendheaders message tells the receiving peer to send new block announcements using a headers message rather than an inv message.

There is no payload in a sendheaders message. See the message header section for an example of a message without a payload.

Spork

Sporks are a mechanism by which updated code is released to the network, but not immediately made active (or “enforced”). Enforcement of the updated code can be activated remotely. Should problems arise, the code can be deactivated in the same manner, without the need for a network-wide rollback or client update.

A spork message may be sent in response to a getsporks message.

The spork message tells the receiving peer the status of the spork defined by the SporkID field. Upon receiving a spork message, the client must verify the signature before accepting the spork message as valid.

Defined Sporks (per src/spork.h)

To verify vchSig, compare the hard-coded spork public key (strSporkPubKey from src/chainparams.cpp) with the public key recovered from the spork message’s hash and vchSig value (implementation details for Dash Core can be found in CPubKey::RecoverCompact). The hash is a double SHA-256 hash of:

• The spork magic message ("DarkCoin Signed Message:\n")
• nSporkID + nValue + nTimeSigned

The following annotated hexdump shows a spork message.

11270000 .................................... Spork ID: Spork 2 InstantSend enabled (10001)
0000000000000000 ............................ Value (0)
2478da5900000000 ............................ Epoch time: 2017-10-08 19:10:28 UTC (1507489828)

41 .......................................... Signature length: 65

1b6762d3e70890b5cfaed5d1fd72121c
d32020c827a89f8128a00acd210f4ea4
1b36c26c3767f8a24f48663e189865ed
403ed1e850cdb4207cdd466419d9d183
45 .......................................... Masternode Signature

VerAck

The verack message acknowledges a previously-received version message, informing the connecting node that it can begin to send other messages. The verack message has no payload; for an example of a message with no payload, see the message headers section.

Version

The version message provides information about the transmitting node to the receiving node at the beginning of a connection. Until both peers have exchanged version messages, no other messages will be accepted.

If a version message is accepted, the receiving node should send a verack message—but no node should send a verack message before initializing its half of the connection by first sending a version message.

The following service identifiers have been assigned.

The following annotated hexdump shows a version message. (The message header has been omitted and the actual IP addresses have been replaced with RFC5737 reserved IP addresses.)

3e120100 .................................... Protocol version: 70206
0500000000000000 ............................ Services: NODE_NETWORK (1) + NODE_BLOOM (4)
bc8f5e5400000000 ............................ Epoch time: 1415483324

0100000000000000 ............................ Receiving node's services
00000000000000000000ffffc61b6409 ............ Receiving node's IPv6 address
270f ........................................ Receiving node's port number

0500000000000000 ............................ Transmitting node's services
00000000000000000000ffffcb0071c0 ............ Transmitting node's IPv6 address
270f ........................................ Transmitting node's port number

128035cbc97953f8 ............................ Nonce

14 .......................................... Bytes in user agent string: 20
2f4461736820436f72653a302e31322e312e352f..... User agent: /Satoshi:0.9.2.1/

851f0b00 .................................... Start height: 728965
01 .......................................... Relay flag: true

InstantSend Messages

The following network messages all help control the InstantSend feature of Dash. InstantSend uses the masternode network to lock transaction inputs and enable secure, instantaneous transactions. For additional details, refer to the Developer Guide InstantSend section.

ix

The ix message (transaction lock request) has the same structure as the tx message. The masternode network responds with txlvote messages if the transaction inputs can be locked.

txlvote

The txlvote message (transaction lock vote) is sent by masternodes to indicate approval of a transaction lock request ix message.

The following annotated hexdump shows a txlvote message. (The message header has been omitted.)

3c121fb4a12b2f715e2f70a9fa282115
be197dde14073959fb2a2b8e95a7418f ..... TXID

Outpoint to lock
| bb607995757c6a6efd6429215dcb3688
| b252d34d835c81fed310fd905f487020 ... Outpoint TXID
| 01000000 ........................... Outpoint index number: 1

Masternode Outpoint
| de9029c7e9b7eb7cd11f27ba670b2349
| 0c3f0717b86ed949c316874589405cd2 ... Outpoint TXID
| 00000000 ........................... Outpoint index number: 0

41 ................................... Signature length: 65

1ccc39ffb9c62111a8c82823d3ce61d2
380db4e8f76ec238d568908f37558a90
4e79566a53663de12ec2be1183c87d61
250e8ebd57be171be1d4b5e89b69c263
88 ................................... Masternode Signature

PrivateSend Messages

The following network messages all help control the PrivateSend (formerly DarkSend) coin mixing features built in to Dash and facilitated by the masternode network.

Since the messages are all related to a single process, this diagram shows them sequentially numbered. The dssu message (not shown) is sent by the masternode in conjunction with some responses. For additional details, refer to the Developer Guide PrivateSend section.

dsa

The dsa message allows a node to join a mixing pool. A collateral fee is required and may be forfeited if the client acts maliciously. The message operates in two ways:

1. When sent to a masternode without a current mixing queue, it initiates the start of a new mixing queue

2. When sent to a masternode with a current mixing queue, it attempts to join the existing queue

Dash Core starts a new queue ~33% of the time and attempts to join an existing queue the remainder of the time.

The following annotated hexdump shows a dsa message. (The message header has been omitted.)

02000000 ................................... Denomination: 1 Dash (2)

Collateral Transaction
| Previous Output
| |
| | 010000000183bd1980c71c38f035db9b
| | 14d7f934f7d595181b3436e362899026 ....... Outpoint TXID
| | 19f3f7d3 ............................... Outpoint index number: 3556242201
|
| 83 ....................................... Bytes in sig. script: 131
|
| 000000006b483045022100f4d8fa0ae4132235fe
| cd540a62715ccfb1c9a97f8698d066656e30bb1e
| 1e06b90220301b4cc93f38950a69396ed89dfcc0
| 8e72ec8e6e7169463592a0bf504946d98b812102
| fa4b9c0f9e76e06d57c75cab9c8368a62a1ce8db
| 6eb0c25c3e0719ddd9ab549cffffffff01e09304
| 00000000001976a914f895 ................... Secp256k1 signature: None
|
| 6a4eb0e5 ................................. Sequence number: 3853536874

dsc

The dsc message indicates a PrivateSend mixing session is complete.

Reference the Message IDs table under the dssu message for descriptions of the Message ID values.

The following annotated hexdump shows a dsc message. (The message header has been omitted.)

d9070700 ............................. Session ID: 791686
14000000 ............................. Message ID: MSG_SUCCESS (20)

dsf

The dsf message is sent by the masternode as the final mixing transaction in a PrivateSend mixing session. The masternode expects nodes in the mixing session to respond with a dss message.

The following annotated hexdump shows a dsf message. (The message header has been omitted.) Transaction inputs/outputs are only shown for a single node (compare with the dsi message and dss message hexdumps).

86140c00 ............................. Session ID: 791686

Transaction Message
| 01000000 ................................. Version: 1
|
| 0f ......................................... Number of inputs: 15
|
| [...] ...................................... 5 transaction inputs omitted
|
| Transaction input #6
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 02000000 ................................. Outpoint index number: 0
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #7
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0f000000 ................................. Outpoint index number: 15
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #8
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0d000000 ................................. Outpoint index number: 13
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
|
| [...] ...................................... 7 more transaction inputs omitted
|
|
| 0f ......................................... Number of outputs: 15
|
| Transaction output #1
| | e8e4f50500000000 ......................... Duffs (1.00001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | 14826d7ba05cf76588a5503c03951dc9
| | | | 14c91b6c ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
|
| [...] ...................................... 3 transaction outputs omitted
|
|
| Transaction output #5
| | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | 426614716e94812d483bca32374f6ac8
| | | | cd121b0d ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
|
| [...] ...................................... 9 transaction outputs omitted
|
|
| Transaction output #15
| | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | f01197177de2358928196a543b2bbd97
| | | | 3c2ab002 ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
| 00000000 ................................... locktime: 0 (a block height)

dsi

The dsi message replies to a dsq message that has the Ready field set to 0x01. The dsi message contains user inputs for mixing along with the outputs and a collateral. Once the masternode receives dsi messages from all members of the pool, it responds with a dsf message.

The following annotated hexdump shows a dsi message. (The message header has been omitted.)

User inputs
| 03 ......................................... Number of inputs: 3
|
| Transaction input #1
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 02000000 ................................. Outpoint index number: 2
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #2
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0f000000 ................................. Outpoint index number: 15
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #3
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0d000000 ................................. Outpoint index number: 13
| |
| | 00 ....................................... Bytes in sig. script: 0
| | .......................................... Secp256k1 signature: None
| |
| | ffffffff ................................. Sequence number: UINT32_MAX

Collateral Transaction
| 01000000 ................................... Version: 1
|
| 01 ......................................... Number of inputs: 1
|
| Previous Output
| |
| | 83bd1980c71c38f035db9b14d7f934f7
| | d595181b3436e36289902619f3f7d383 ......... Outpoint TXID
| | 00000000 ................................. Outpoint index number: 0
| |
| | 6b ....................................... Bytes in sig. script: 107
| |
| | 483045022100f4d8fa0ae4132235fecd540a
| | 62715ccfb1c9a97f8698d066656e30bb1e1e
| | 06b90220301b4cc93f38950a69396ed89dfc
| | c08e72ec8e6e7169463592a0bf504946d98b
| | 812102fa4b9c0f9e76e06d57c75cab9c8368
| | a62a1ce8db6eb0c25c3e0719ddd9ab549c ....... Secp256k1 signature
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| 01 ......................................... Number of outputs: 1
|
| | e093040000000000 ......................... 300,000 Duffs (0.003 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | f8956a4eb0e53b05ee6b30edfd2770b5
| | | | 26c1f1bb ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
| 00000000 ................................... locktime: 0 (a block height)

User outputs
| 03 ......................................... Number of outputs: 3
|
| Transaction output #1
| | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | 14826d7ba05cf76588a5503c03951dc9
| | | | 14c91b6c ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
| Transaction output #2
| | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | f01197177de2358928196a543b2bbd97
| | | | 3c2ab002 ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
| Transaction output #3
| | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | 426614716e94812d483bca32374f6ac8
| | | | cd121b0d ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG

dsq

The dsq message provides nodes with mixing queue details and notifies them when to sign final mixing TX messages.

If the message indicates the queue is not ready, the node verifies the message is valid. It also verifies that the masternode is not flooding the network with dsq messages in an attempt to dominate the queuing process. It then relays the message to its connected peers.

If the message indicates the queue is ready, the node responds with a dsi message.

Denominations (per src/privatesend.cpp)

The following annotated hexdump shows a dsq message. (The message header has been omitted.)

08000000 ............................. Denomination: 0.01 Dash (8)

Masternode Outpoint
| aeed0e77c6db30a616507a37a129bc88
| 1811f08afc51dd485d5322f36c1f04c5 ... Outpoint TXID
| 01000000 ........................... Outpoint index number: 1

1318a85900000000 ..................... Create Time: 2017-08-31 14:07:15 UTC

00 ................................... Ready: 0

41 ................................... Signature length: 65

1bd74386ea4e111197f1b4b4660c1415
13486745ca10ba0632426ed3a644d941
047e43c988680904d4a4fcf551d8813c
ec12d47ae9b00e870db294cd66708ab7
dc ................................... Masternode Signature

dss

The dss message replies to a dsf message sent by the masternode managing the mixing session. The dsf message provides the unsigned transaction inputs for all members of the mixing pool. Each node verifies that the final transaction matches what is expected. They then sign any transaction inputs belonging to them and then relay them to the masternode via this dss message.

Once the masternode receives and validates all dss messages, it issues a dsc message. If a node does not respond to a dsf message with signed transaction inputs, it may forfeit the collateral it provided. This is to minimize malicious behavior.

The following annotated hexdump shows a dss message. (The message header has been omitted.) Note that these will be the same transaction inputs that were supplied (unsiged) in the dsi message.

User inputs
| 03 ......................................... Number of inputs: 3
|
| Transaction input #1
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 02000000 ................................. Outpoint index number: 2
| |
| | 6b ....................................... Bytes in sig. script: 107
| | 483045022100b3a861dca83463aabf5e4a14a286
| | 1b9c2e51e0dedd8a13552e118bf74eb4a68d0220
| | 4a91c416768d27e6bdcfa45d28129841dbcc728b
| | f0bbec9701cfc4e743d23adf812102cc4876c9da
| | 84417dec37924e0479205ce02529bb0ba88631d3
| | ccc9cfcdf00173 ........................... Secp256k1 signature
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #2
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0f000000 ................................. Outpoint index number: 15
| |
| | 6a ....................................... Bytes in sig. script: 106
| | 4730440220268f3b7799ca4ec132e511a4756019
| | c56016f7771561dc0597d84e9b1fa9fc08022067
| | 5199b9b3f9a7eba69b7bbb4aa2a413d955762f9d
| | 68be5a9c02c6772c8078fd812103258925f0dbbf
| | 9d5aa20a675459fa2e86c9f9061dee82a00dca73
| | 9080f051d891 ............................. Secp256k1 signature
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| Transaction input #3
| |
| | 36bdc3796c5630225f2c86c946e2221a
| | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID
| | 0d000000 ................................. Outpoint index number: 13
| |
| | 6a ....................................... Bytes in sig. script: 106
| | 4730440220404bb067e0c94a2bd75c6798c1af8c
| | 95e8b92f5e437cff2bcb4660f24a34d06d02203a
| | b707bd371a84a9e7bd1fbe3b0c939fd23e0a9165
| | de78809b9310372a4b3879812103a9a6c5204811
| | a8cab04b595ed622a1fed6efd3b2d888fadd0c97
| | 3737fcdf2bc7 ............................. Secp256k1 signature
| |
| | ffffffff ................................. Sequence number: UINT32_MAX

dssu

The dssu message provides a mixing pool status update.

Pool State

Pool Status Update

Message IDs

The following annotated hexdump shows a dssu message. (The message header has been omitted.)

86140c00 ............................. Session ID: 791686
02000000 ............................. State: POOL_STATE_ACCEPTING_ENTRIES (2)
03000000 ............................. Entries: 3
01000000 ............................. Status Update: STATUS_ACCEPTED (1)
13000000 ............................. Message ID: MSG_NOERR (0x13)

dstx

The dstx message allows masternodes to broadcast subsidized transactions without fees (to provide security in mixing).

The following annotated hexdump shows a dstx message. (The message header has been omitted.)

Transaction Message
| 01000000 ................................. Version: 1
|
| 0b ......................................... Number of inputs: 11
|
| Transaction input #1
| |
| | 0adb782b2170018eada54534be880e70
| | 74ed8307a566731119b1782362af43ad ......... Outpoint TXID
| | 05000000 ................................. Outpoint index number: 5
| |
| | 6a ....................................... Bytes in sig. script: 106
| | 47304402204ed56f525ae6df707f9cbe
| | 55c78d82bbcc02daa1fb27b0bf54588a
| | 446dcc804102200c4e03c4a2b9a90aef
| | 9f01de7c28812a0e8b280e6c153b0bd8
| | 26d2ff660102e18121028c96903b2709
| | 7b331d55abd1f42d2ff6cc7c784ab839
| | 7c232b73a34a149a348e ..................... Secp256k1 signature
| |
| | ffffffff ................................. Sequence number: UINT32_MAX
|
| [...] ...................................... 10 more transaction inputs omitted
|
|
| 0b ......................................... Number of outputs: 11
|
| Transaction output #1
| | e8e4f50500000000 ......................... Duffs (1.00001000 Dash)
| |
| | 19 ....................................... Bytes in pubkey script: 25
| | | 76 ..................................... OP_DUP
| | | a9 ..................................... OP_HASH160
| | | 14 ..................................... Push 20 bytes as data
| | | | 0febbeaa8818b2c2f80fb8c98f90bdae
| | | | 41fe5c26 ............................. PubKey hash
| | | 88 ..................................... OP_EQUALVERIFY
| | | ac ..................................... OP_CHECKSIG
|
| [...] ...................................... 10 more transaction outputs omitted
|
|
| 00000000 ................................... locktime: 0 (a block height)

Masternode Unspent Output
| 387d522def2abfb9bdd15be899f074f3
| 49b414cef078ec642e1d14b42996b9fc ......... Outpoint TXID
| 00000000 ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature (None)
|
| ffffffff ................................. Sequence number: UINT32_MAX

1b6fb8f90f0df6e502bc10aab9604e49
2d14214e05331c9761c834d55c7536e3
3369e5909479ea88116aad7ea64587d9
59364326c97d7f249f7b9293e120a5b6
1c ................................... Masternode Signature

ece5a95900000000 ..................... Signature Timestamp

Masternode Messages

The following network messages enable the masternode features built in to Dash.

For additional details, refer to the Developer Guide Masternode Sync and Masternode Payment sections.

dseg

The dseg message requests either the entire masternode list or a specific entry. To request the list of all masternodes, use an empty txIn (TXID of all zeros and an index of 0xFFFFFFFF). To request information about a specific masternode, use the unspent output associated with that masternode.

The response to a dseg message is an mnb message inventory and an mnp message inventory for each requested masternode. Masternodes ignore this request if they are not fully synced.

Note: Dash Core only allows nodes to request the entire list every 3 hours.
Additional requests sent prior to then may result in the node being banned.

The following annotated hexdump shows a dseg message requesting all masternodes. (The message header has been omitted.)

Masternode Unspent Output
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ......... Outpoint TXID
| ffffffff ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

The following annotated hexdump shows a dseg message requesting a specific masternode. (The message header has been omitted.)

Masternode Unspent Output
| 7fe33a2901aa654598ae0af572d4fbec
| ee97af2d0276f189d177dee5848ef3da ......... Outpoint TXID
| 00000000 ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

mnb

The mnb message is sent whenever a masternode comes online or a client is syncing. The masternode will send this message which describes the masternode entry and how to validate messages from it.

The following annotated hexdump shows a mnb message. (The message header has been omitted and the actual IP address has been replaced with a RFC5737 reserved IP address.)

Masternode Unspent Output
| 3fbc7d4a8f68ba6ecb02a8db34d1f5b6
| 2dc105f0b5c3505243435cf815d02394 ......... Outpoint TXID
| 01000000 ................................. Outpoint index number: 1
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

Masternode Address
| 00000000000000000000ffffc0000233 ......... IP Address: ::ffff:192.0.2.51
| 270f ..................................... Port: 9999

Collateral Public Key
| 21 ....................................... Key Size: 33
| 02 ....................................... Key Type: 2 - Compressed (even)
| 02a47a6845936a4199e126d35399dd09
| 97c1aaf89a3fe70d474c53f29624a43a5b ....... Public Key

Masternode Public Key
| 41 ....................................... Key Size: 65
| 04 ....................................... Key Type: 4 - Uncompressed
| 04da252243305d604cab90480880af4a
| b5cea3a934c91393452e9b7b4c97a87e
| 198bc809916ac2c27436a1db9c28d0aa
| bfefec4dc3c2193835fd9a56c31150c633 ....... Public Key

Message Signature
| 41 ....................................... Bytes in signature: 65
| 1fb80f9ba8c110835e4a7dd4c8deccd7
| 89027663d00084d9a99ef579a9b5601f
| 40727b27e91aab2897a078f63976ae25
| 3ff8f01e56862e953278f432530f6ee080 ....... Signature

4728ef5800000000 ........................... Sig. Timestamp: 2017-04-13 07:27:03 UTC

3e120100 ................................... Protocol Version: 70206

Masternode Ping Message
| Masternode Unspent Output
| | 3fbc7d4a8f68ba6ecb02a8db34d1f5b6
| | 2dc105f0b5c3505243435cf815d02394 ........ Outpoint TXID
| | 01000000 ................................ Outpoint index number: 1
| |
| | 00 ...................................... Bytes in sig. script: 0
| | ......................................... Secp256k1 signature: None
| |
| | ffffffff ................................ Sequence number: UINT32_MAX
|
| 94fc0fad18b166c2fedf1a5dc0511372
| 26c353d57e086737ff05000000000000 ......... Chaintip block hash
|
| 66c1a95900000000 ......................... Sig. Timestamp: 2017-10-01 21:21:58 UTC
|
| Masternode Signature
| | 41 ..................................... Bytes in signature: 65
| | 1b3017c49a03e2d77083f3c92a8c2e4c
| | d815d068b6256498a719e3cb6a34f774
| | ec6434cfcbb7a5a51704350a05903287
| | eecc82e6b40ac2fcfa2df29ddaa6c4fc
| | b8 ..................................... Masternode Signature

mnget

The mnget message requests masternode payment sync. The response to an mnget message is mnw message inventories (up to the number asked for in the request). Masternodes ignore this request if they are not fully synced.

Note: Dash Core limits how frequently a masternode payment sync can be
requested. Frequent requests will result in the node being banned.

The following annotated hexdump shows a mnget message. (The message header has been omitted.)

a8170000 ................................... Count: 6056

mnp

The mnp message is sent by masternodes every few minutes to ping the network with a message that propagates across the whole network. Dash Core currently uses a minimum masternode ping time of 10 minutes.

The following annotated hexdump shows a mnp message. (The message header has been omitted.)

Masternode Unspent Output
| 0bfa3616099771bb5f36181ff4060a9b
| 9afe7b3e47d7f4327800f0f8ce586c6e ......... Outpoint TXID
| 01000000 ................................. Outpoint index number: 1
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

a26a68ebb733192c1c40f9b42f872ac0
e23d4c360e20d5ab6608000000000000 ........... Chaintip block hash

1bbfa95900000000 ........................... Sig. Timestamp: 2017-10-01 20:12:11 UTC

Masternode Signature
| 41 ....................................... Bytes in signature: 65
| 1c2b205bd6ba472d7a9495f049ef66dc
| f844154846e25f2389385ba2d3e95cde
| cf3ccf82bc26d94c6fdafcd7b965bb61
| db02d05483595196ea4d92b2e797612b
| 79 ....................................... Masternode Signature

mnv

The mnv message is used by masternodes to verify each other. Several mnv messages are exchanged in the process. This results in the IP address of masternode 1 being validated as of the provided block height.

Initially, vin1, vin2, vchSig1 and vchSig2 are empty. They are updated as the exchange of messages between the masternodes occurs as detailed in the table below.

Masternode Verify Data Flow

Nodes receiving a relayed mnv message (one in which vin1, vin2, vchSig1 and vchSig2 are already present) use it to update the PoSe ban score. If the ban score reaches MASTERNODE_POSE_BAN_MAX_SCORE (5), the masternode will be considered malicious and banned. If the received message is valid, nodes receiving it will relay it on to their connected peers.

Important Notes:
* Dash Core limits how frequently a masternode verify request can be
  requested. Frequent requests will result in the node being banned.

* Only masternodes in the top `MAX_POSE_RANK` (10) can send an `mnv` request
  (to no more than `MAX_POSE_CONNECTIONS` (10)).

The following annotated hexdump shows a mnv message. This is an example of the initial request (Step 1) so it does not contain any signatures. (The message header has been omitted.)

Masternode 1 Unspent Output (empty)
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ......... Outpoint TXID
| ffffffff ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

Masternode 2 Unspent Output (empty)
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ......... Outpoint TXID
| ffffffff ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

00000000000000000000ffff2d20ed4c ........... IP Address: ::ffff:45.32.237.76
4e1f ....................................... Port: 19999
9d090000 ................................... Nonce: 2641
ed5c0000 ................................... Block height: 23789

Masternode 1 Signature
| 00 ....................................... Bytes in signature: 0
| .......................................... Signature: Empty

Masternode 2 Signature
| 00 ....................................... Bytes in signature: 0
| .......................................... Signature: Empty

The following annotated hexdump shows a mnv message. This is an example of the initial response (Step 2) so it only contains the signature of masternode 1 (the masternode being verified). (The message header has been omitted.)

Masternode 1 Unspent Output (empty)
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ......... Outpoint TXID
| ffffffff ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

Masternode 2 Unspent Output (empty)
| 00000000000000000000000000000000
| 00000000000000000000000000000000 ......... Outpoint TXID
| ffffffff ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

00000000000000000000ffff2d20ed4c ........... IP Address: ::ffff:45.32.237.76
4e1f ....................................... Port: 19999
9d090000 ................................... Nonce: 2641
ed5c0000 ................................... Block height: 23789

Masternode 1 Signature
| 41 ....................................... Bytes in signature: 65
| 1bf5bd6e6eda0cd32aafb826c4066fa5
| 4a53baa6f4211528e51716054b4df981
| d97a77e633947bbbfafd6882324b76a0
| 90c6e65c16ca1222db48f8558537c062
| f6 ....................................... Signature

Masternode 2 Signature
| 00 ....................................... Bytes in signature: 0
| .......................................... Signature: Empty

mnw

The mnw message is used to pick the next winning masternode. When a new block is found on the network, a masternode quorum will be determined and those 10 selected masternodes will issue the masternode payment vote message.

The following annotated hexdump shows a mnw message. (The message header has been omitted.)

Masternode Unspent Output
| 0c1b5c5846792b25b05eeea9586d8c34
| ecb996c566bedb4ecf6a68fe8ffa9582 ......... Outpoint TXID
| 00000000 ................................. Outpoint index number: 0
|
| 00 ....................................... Bytes in sig. script: 0
| .......................................... Secp256k1 signature: None
|
| ffffffff ................................. Sequence number: UINT32_MAX

fb4f0a00 ................................... Block pay height: 675835

Payee Address
| 19 ....................................... Address Length: 25
| | 76 ..................................... OP_DUP
| | a9 ..................................... OP_HASH160
| | 14 ..................................... Push 20 bytes as data
| | | 1767c363646be7d8e4475c0aa85ea454
| | | 9fd102c4 ............................. Pubkey hash
| | 88 ..................................... OP_EQUALVERIFY
| | ac ..................................... OP_CHECKSIG

Masternode Signature
| 41 ....................................... Bytes in signature: 65
| 1c25da47190a83937fb5ef607235703a
| 7cdda155bf5a1ae6139929024750f899
| a90a4f57cdf9d54c9d9603c1f31009f8
| e257355b49c0484fb4c31bc412c73dd9
| 20 ....................................... Signature

mnwb

There is no message for mnwb (inv message only).

The following annotated hexdump shows an inv message with a mnwb inventory entry. (The message header has been omitted.)

01 ................................. Count: 1

08000000 ........................... Type: MSG_MASTERNODE_PAYMENT_BLOCK (8)
dd6cc6c11211793b239c2e311f1496e2
2281b200b35233eaae465d2aa3c9d537 ... Hash: mnwb

ssc

The ssc message is used to track the sync status of masternode objects. This message is sent in response to sync requests for the list of masternodes (dseg message), masternode payments (mnget message), governance objects (govsync message), and governance object votes (govsync message).

Sync Item IDs

The following annotated hexdump shows a ssc message. (The message header has been omitted.)

02000000 ................................... Item ID: MASTERNODE_SYNC_LIST (2)
bf110000 ................................... Count: 4543

Governance Messages

The following network messages enable the Governance features built in to Dash. For additional details on the governance system, see this Budget System page.

For additional details, refer to the Developer Guide Governance section.

govobj

The govobj message contains a governance object that is generally a proposal, contract, or setting. Masternodes ignore this request if they are not fully synced.

Governance Object Types (defined by src/governance-object.h)

The following annotated hexdump shows a govobj message for a Proposal object. Notice the presence of a non-zero collateral hash, a vinMasternode that is an empty CTxIn (hash of all zeros, index/sequence of 0xffffffff, no Signature), and no vchSig. (The message header has been omitted.)

00000000000000000000000000000000
00000000000000000000000000000000 ..... Parent Hash (0 = root)
01000000 ............................. Revision: 1
c8dfd65900000000 ..................... Create timestamp: 2017-10-06 01:43:31 UTC
633611d2f3e7481325242f200c7f3485
e3a9b4b6301e7f7d18d87d8231f3880b ..... Collateral Hash

Data
| 3e02 ............................... Data length: 574
| 356235623232373 ... 376435643564 ... Data (truncated)

01000000 ............................. Object Type: GOVERNANCE_OBJECT_PROPOSAL (1)

Transaction input
| Previous Output
| | 00000000000000000000000000000000
| | 00000000000000000000000000000000 ... Outpoint TXID
| | ffffffff ........................... Outpoint index number: 0
| 00 ................................... Script length: 0
| ...................................... Signature: None
| ffffffff ............................. Sequence

00 ................................... Signature length: 0

| .................................... Masternode Signature (None required)

The following annotated hexdump shows a govobj message for a Trigger object. Notice the collateral hash of all zeros. (The message header has been omitted.)

00000000000000000000000000000000
00000000000000000000000000000000 ..... Parent Hash (0 = root)
01000000 ............................. Revision: 1
911ea85900000000 ..................... Create timestamp: 2017-08-31 14:34:57 UTC
00000000000000000000000000000000
00000000000000000000000000000000 ..... Collateral Hash (None required)

Data
| ae11 ............................... Data length: 4526
| fdae11356235623 ... 376435643564 ... Data (truncated)

02000000 ............................. Object Type: GOVERNANCE_OBJECT_TRIGGER (2)

Transaction input
| Previous Output
| | ffefbe4959085907bcd2ba29e357a441
| | fa7b6e26e25896d8127332bba2419e97 ... Outpoint TXID
| | 00000000 ........................... Outpoint index number: 0
| 00 ................................... Script length: 0
| ...................................... Signature: None
| ffffffff ............................. Sequence

41 ................................... Signature length: 65

1ce3b782f66be8ae9fc4158680128864
341202b6006384083ab2d9cfa73795e2
6000668e84af4ef6a284a52b53843524
72037d51bd9079ffd5c087d9632865ee
75 ................................... Masternode Signature

govobjvote

The govobjvote message is used to indicate the voting status of a governance object. Voting status is comprised of the vote outcome (how the masternode voted) and the vote signal (the network support status). A sufficient number of yes votes results in the proposed funding being payed out in the next superblock (assuming their are sufficient funds available in the budget).

The initial govobjvote message is created by a masternode to vote on a governance object (proposal, etc.). When the masternode votes, it broadcasts the govobjvote message to all its peers.

When a node receives a valid, new govobjvote message, it relays the message to all its connected peers to propagate the vote.

Additionally, nodes can request govobjvote messages for specific governance objects via a govsync message. Masternodes ignore requests for votes if they are not fully synced.

Dash Core limits how frequently a masternode can vote on a governance object.
A masternode's vote will not be processed if it has been less than 60 minutes
since its last vote on that object. Additionally, invalid votes can result in
the node being banned.

Governance Object Vote Signals (defined by src/governance-object.h)

The following annotated hexdump shows a govobjvote message. (The message header has been omitted.)

Transaction input
| Previous Output
| | 57566a0ef85e6cac3415ced67b0b07e1
| | 781bafb853650d7c9d56d8bc132cc3b4 ... Outpoint TXID
| | 00000000 ........................... Outpoint index number: 0
| 00 ................................... Script length: 0
| ...................................... Signature: None
| ffffffff ............................. Sequence

ad9579d5c181eee904156df1c88b050f
b8b4d39e5fda71f015996dbf14a51bff...... Parent Hash (0 = root)
01000000 ............................. Vote Outcome: VOTE_OUTCOME_NONE (1)
02000000 ............................. Vote Signal: VOTE_SIGNAL_VALID (2)
b517a85900000000 ..................... Vote Create Timestamp: 2017-08-31 14:05:41 UTC
00000000000000000000000000000000 ..... Collateral Hash

1b049113a81fe913f061ad295561d267
00b8135a021ab0356a1e89b18d663d0b
dc45e9c09ee0427223e332b52e8d709e
6d64e86b6435d7bdf207d8f23b6ae0db
6f ................................... Masternode Signature

govsync

The govsync message is used to request syncing of governance objects (govobj message and govobjvote message) with peers. Masternodes ignore this request if they are not fully synced.

This message responds in one of two ways depending on the request:

1. Object Sync - When a masternode receives a govsync message with a hash of all zeros, it responds with one ssc message for govobj objects and one for govobjvote objects. The masternode also sends an inv message (MSG_GOVERNANCE_OBJECT - 0x17) for all valid govobj governance objects. Governance object votes are excluded in this type of response.

2. Vote Sync - When a masternode receives a govsync message with a specific hash, it responds with one ssc message for govobj objects and one for govobjvote objects. The masternode also sends both a govobj inventory message (MSG_GOVERNANCE_OBJECT - 0x17) and govobjvote inventory messages (MSG_GOVERNANCE_OBJECT_VOTE - 0x18) for the single governance object requested.

Dash Core limits how frequently the first type of sync (object sync) can be
requested. Frequent requests will result in the node being banned.

The following annotated hexdump shows a govsync message. (The message header has been omitted.)

2e46ea5418e097a3dbcccbee3cf2a911
6fb94ba635153f276dcb2123efcb73ff ..... Hash
00000000000000000000 ................. Bloom Filter

Deprecated Messages

The following network messages have been deprecated and should no longer be used.

mnvs

Masternode Budget Sync - Deprecated since 12.1

mvote

Masternode Budget Vote - Deprecated since 12.1

mprop

Masternode Budget Proposal - Deprecated since 12.1

fbs

Masternode Budget Final - Deprecated since 12.1

fbvote

Masternode Budget Final Vote - Deprecated since 12.1

mn quorum

Not Implemented

Improvement Proposals

Dash (DIPs)

Similar to Bitcoin’s BIPs, a Dash Improvement Proposal (DIP) is a design document for providing information to the Dash community, or describing a new feature for Dash processes/environment. The DIP should provide a concise technical specification of the feature and a rationale for the feature.

DIP Summary Table

Information from Dash DIP repository.

Bitcoin (BIPs)

A Bitcoin Improvement Proposal (BIP) is a design document providing information to the Bitcoin community, or describing a new feature for Bitcoin or its processes or environment.

Since Dash is forked from Bitcoin, some BIPs are applicable to both. The following table provides a list of the BIPs that are relevant to Dash. Some BIPs may only be partially implemented or modified to meet Dash requirements. The Dash Status column indicates if any changes were made.

BIP Summary Table

Dash-specific BIP information derived from Dash developer QuantumExplorer’s BIP repository.

* These BIPs are not Bitcoin or Dash specific (i.e. BIP-0044 Multi-Account Hierarchy for Deterministic Wallets). Generally relates to the Application Layer and not specifically the reference client.

Dash Core APIs

Hash Byte Order

Dash Core RPCs accept and return the byte-wise reverse of computed SHA-256 hash values. For example, the Unix sha256sum command displays the SHA256(SHA256()) hash of mainnet block 300,000’s header as:

> /bin/echo -n '020000007ef055e1674d2e6551dba41cd214debbee34aeb544c7ec670000000000000000d3998963f80c5bab43fe8c26228e98d030edf4dcbe48a666f5c39e2d7a885c9102c86d536c890019593a470d' | xxd -r -p | sha256sum -b | xxd -r -p | sha256sum -b
5472ac8b1187bfcf91d6d218bbda1eb2405d7c55f1f8cc820000000000000000

The result above is also how the hash appears in the previous-header-hash part of block 300,001’s header:

020000005472ac8b1187bfcf91d6d218bbda1eb2405d7c55f1f8cc82000\
0000000000000ab0aaa377ca3f49b1545e2ae6b0667a08f42e72d8c24ae\
237140e28f14f3bb7c6bcc6d536c890019edd83ccf

However, Dash Core’s RPCs use the byte-wise reverse for hashes, so if you want to get information about block 675,776 using the getblock RPC, you need to reverse the requested hash:

> dash-cli getblock \
  000000000000327a66cd1011b2d1defd1417b7d9e39b439e8e67ba996ee92602

(Note: hex representation uses two characters to display each byte of data, which is why the reversed string looks somewhat mangled.)

The rationale for the reversal is unknown, but it likely stems from Dash Core’s use of hashes (which are byte arrays in C++) as integers for the purpose of determining whether the hash is below the network target. Whatever the reason for reversing header hashes, the reversal also extends to other hashes used in RPCs, such as TXIDs and merkle roots.

As header hashes and TXIDs are widely used as global identifiers in other Dash software, this reversal of hashes has become the standard way to refer to certain objects. The table below should make clear where each byte order is used.

Note: RPCs which return raw results, such as getrawtransaction or the raw mode of getblock, always display hashes as they appear in blocks (internal byte order).

The code below may help you check byte order by generating hashes from raw hex.

#!/usr/bin/env python

from sys import byteorder
from hashlib import sha256

## You can put in $data an 80-byte block header to get its header hash,
## or a raw transaction to get its txid
data = "00".decode("hex")
hash = sha256(sha256(data).digest()).digest()

print "Warning: this code only tested on a little-endian x86_64 arch"
print
print "System byte order:", byteorder
print "Internal-Byte-Order Hash: ", hash.encode('hex_codec')
print "RPC-Byte-Order Hash:      ", hash[::-1].encode('hex_codec')

Remote Procedure Calls (RPCs)

Dash Core provides a remote procedure call (RPC) interface for various administrative tasks, wallet operations, and queries about network and block chain data.

If you start Dash Core using dash-qt, the RPC interface is disabled by default. To enable it, set server=1 in dash.conf or supply the -server argument when invoking the program. If you start Dash Core using dashd, the RPC interface is enabled by default.

The interface requires the user to provide a password for authenticating RPC requests. This password can be set either using the rpcpassword property in dash.conf or by supplying the -rpcpassword program argument. Optionally a username can be set using the rpcuser configuration value. See the Examples Page for more information about setting Dash Core configuration values.

Open-source client libraries for the RPC interface are readily available in most modern programming languages, so you probably don’t need to write your own from scratch. Dash Core also ships with its own compiled C++ RPC client, dash-cli, located in the bin directory alongside dashd and dash-qt. The dash-cli program can be used as a command-line interface (CLI) to Dash Core or for making RPC calls from applications written in languages lacking a suitable native client. The remainder of this section describes the Dash Core RPC protocol in detail.

The Dash Core RPC service listens for HTTP POST requests on port 9998 in mainnet mode, 19998 in testnet, or 18332 in regtest mode. The port number can be changed by setting rpcport in dash.conf. By default the RPC service binds to your server’s localhost loopback network interface so it’s not accessible from other servers. Authentication is implemented using HTTP basic authentication. RPC HTTP requests must include a Content-Type header set to text/plain and a Content-Length header set to the size of the request body.

The format of the request body and response data is based on version 1.0 of the JSON-RPC specification. Specifically, the HTTP POST data of a request must be a JSON object with the following format:

In the table above and in other tables describing RPC input and output, we use the following conventions

• “→” indicates an argument that is the child of a JSON array or JSON object. For example, “→ → Parameter” above means Parameter is the child of the params array which itself is a child of the Request object.

• Plain-text names like “Request” are unnamed in the actual JSON object

• Code-style names like params are literal strings that appear in the JSON object.

• “Type” is the JSON data type and the specific Dash Core type.

• “Presence” indicates whether or not a field must be present within its containing array or object. Note that an optional object may still have required children.

The HTTP response data for a RPC request is a JSON object with the following format:

As an example, here is the JSON-RPC request object for the hash of the genesis block:

{
    "method": "getblockhash",
    "params": [0],
    "id": "foo"
}

The command to send this request using dash-cli is:

dash-cli getblockhash 0

Alternatively, we could POST this request using the cURL command-line program as follows:

curl --user 'my_username:my_secret_password' --data-binary '''
  {
      "method": "getblockhash",
      "params": [0],
      "id": "foo"
  }''' \
  --header 'Content-Type: text/plain;' localhost:9998

The HTTP response data for this request would be:

{
    "result": "00000ffd590b1485b3caadc19b22e6379c733355108f107a430458cdf3407ab6",
    "error": null,
    "id": "foo"
}

Note: In order to minimize its size, the raw JSON response from Dash Core doesn’t include any extraneous whitespace characters. Here we’ve added whitespace to make the object more readable. Speaking of which, dash-cli also transforms the raw response to make it more human-readable. It:

• Adds whitespace indentation to JSON objects
• Expands escaped newline characters (“\n”) into actual newlines
• Returns only the value of the result field if there’s no error
• Strips the outer double-quotes around results of type string
• Returns only the error field if there’s an error

Continuing with the example above, the output from the dash-cli command would be simply:

00000ffd590b1485b3caadc19b22e6379c733355108f107a430458cdf3407ab6

If there’s an error processing a request, Dash Core sets the result field to null and provides information about the error in the error field. For example, a request for the block hash at block height -1 would be met with the following response (again, whitespace added for clarity):

{
    "result": null,
    "error": {
        "code": -8,
        "message": "Block height out of range"
    },
    "id": "foo"
}

If dash-cli encounters an error, it exits with a non-zero status code and outputs the error field as text to the process’s standard error stream:

error code: -8
error message:
Block height out of range

The RPC interface supports request batching as described in version 2.0 of the JSON-RPC specification. To initiate multiple RPC requests within a single HTTP request, a client can POST a JSON array filled with Request objects. The HTTP response data is then a JSON array filled with the corresponding Response objects. Depending on your usage pattern, request batching may provide significant performance gains. The dash-cli RPC client does not support batch requests.

curl --user 'my_username:my_secret_password' --data-binary '''
  [
    {
      "method": "getblockhash",
      "params": [0],
      "id": "foo"
    },
    {
      "method": "getblockhash",
      "params": [1],
      "id": "foo2"
    }
  ]''' \
  --header 'Content-Type: text/plain;' localhost:9998

To keep this documentation compact and readable, the examples for each of the available RPC calls will be given as dash-cli commands:

dash-cli [options] <method name> <param1> <param2> ...

This translates into an JSON-RPC Request object of the form:

{
    "method": "<method name>",
    "params": [ "<param1>", "<param2>", "..." ],
    "id": "foo"
}

Warning: if you write programs using the JSON-RPC interface, you must ensure they handle high-precision real numbers correctly. See the Proper Money Handling Bitcoin Wiki article for details and example code.

Quick Reference

RPC Summary Table

Type part of the Name or Type of an RPC to filter the list: