Add DIP9 - Feature derivation paths (#48)

* DIP9 - Add DIP and assignment documents

* DIP9 - Add to Readme

README.md

@@ -26,6 +26,7 @@ Number | Layer | Title | Owner | Type | Status
 [6](dip-0006.md) | Consensus | Long-Living Masternode Quorums | Alexander Block | Standard | Active
 [7](dip-0007.md) | Consensus | LLMQ Signing Requests / Sessions | Alexander Block | Standard | Active
 [8](dip-0008.md) | Consensus | ChainLocks | Alexander Block | Standard | Active
+[9](dip-0009.md) | Applications | Feature Derivation Paths | Samuel Westrich | Informational | Proposed
 [10](dip-0010.md) | Consensus | LLMQ InstantSend | Alexander Block | Standard | Proposed
 
 

dip-0009.md

@@ -0,0 +1,70 @@
+<pre>
+  DIP: 0009
+  Title: Feature Derivation Paths
+  Author(s): Samuel Westrich
+  Special-Thanks:  
+  Status: Proposed
+  Type: Informational
+  Created: 2019-03-12
+  License: MIT License
+</pre>
+
+## Table of Contents
+
+1.  [Abstract](#abstract)
+1.  [Motivation](#motivation)
+1.  [Prior Work](#prior-work)
+1.  [Feature Path Level](#feature-path-level)
+1.  [Copyright](#copyright)
+
+## Abstract
+
+This DIP introduces reliable derivation paths for various coin-specific features.
+
+## Motivation
+
+Currently there is much ambiguity between different coin paths, BIP43 tried to solve this with the ‘purpose’ hardened derivation. With BIP44 we saw derivation paths such as `44’/5’/0’` which addresses coin-specific derivation paths. However, these derivation paths had an account directly after the coin type which made it unusable for coin-specific features other than standard transactions.
+
+## Prior work
+
+- [BIP-0043 - Purpose Field for Deterministic Wallets](https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki)
+- [BIP-0044 - Multi-Account Hierarchy for Deterministic Wallets](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki)
+
+## Feature path level
+
+We define the following minimum 3 levels in BIP32 path:
+
+  `m / purpose' / coin_type' / feature' / *`
+
+An apostrophe in the path indicates that BIP32 hardened derivation is used.
+
+Each level has a special meaning, described in the sections below.
+
+### Purpose
+
+Purpose is a constant set to `9'` (or 0x80000009) following the [BIP43 recommendation](https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki#purpose). It indicates that the subtree of this node is used according to this specification.
+
+Hardened derivation is used at this level.
+
+### Coin type
+
+Coin type in this DIP is the same as defined by [BIP44](https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki#coin-type) (a constant, set for each cryptocoin). For example, Dash has a registered coin type of `5'` (or 0x80000005).
+
+This DIP is not a central directory for the registered coin types. Please visit the full list of registered coin types maintained by SatoshiLabs for any other coins:
+
+[SLIP-0044 : Registered coin types for BIP-0044](https://github.com/satoshilabs/slips/blob/master/slip-0044.md)
+
+Hardened derivation is used at this level.
+
+### Feature
+
+This level splits the coin’s key space based on coin-specific features.  For example, it may be desirable to maintain mixed funds in a path that is isolated from non-mixed funds. Other use cases could include using a specific path for identity or other non-financial keys.
+
+Hardened derivation is used at this level.
+
+Feature derivation paths may be defined based on future DIPs. A list of registered features can be found [here](dip-0009/assignments.md).
+
+
+## Copyright
+
+Copyright (c) 2019 Dash Core Group, Inc. [Licensed under the MIT License](https://opensource.org/licenses/MIT)

dip-0009/assignments.md

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+## Registered Features
+
+Here is a table of current feature paths and any associated DIP. Future DIPs may introduce more types.
+
+
+| Feature Index * | Feature | DIP Number and Name | Note |
+| ------------------ | ------------ | ------------------- | ---- |
+| `3'` | Masternode Keys | [DIP 0003: Deterministic Masternode List](https://github.com/dashpay/dips/blob/master/dip-0003.md) | The masternode related keys are located in the following sub-paths:  <br>0'/* - _Reserved_<br>1'/* - Voting Key<br>2'/* - Owner Key<br>3'/* - Operator Key<br><br>For example, the first voting key for Dash would be at `m/9'/5'/3'/1'/0` |
+
+Note: all DIP 0009 paths are of the format: `m / 9' / coin_type' / feature' / *`
+
+\* Where applicable, the feature index matches the number of the DIP that defines the feature(s)