digraph extended {

size=6.25;
rankdir=LR;
penwidth=1.75;
node [ fontname="Sans", penwidth = 1.75, shape = "box" ];
edge [ fontname="Sans", penwidth = 1.75 ];
graph [ fontname="Sans" ]
nodesep=0.15;
//splines = ortho;
ranksep = 0.3;

subgraph cluster_parent {
style = "invis";
parent_private_key [ label = "Parent Private Key" ];
parent_chain_code [ label = "Parent Chain Code" ];
parent_public_key [ label = "Parent Public Key" ];
}

child_private_key [ label = "Child Private Key" ];
child_chain_code [ label = "Child Chain Code" ];
child_public_key [ label = "Child Public Key" ];

i_norm [ label = "Index Number" ];
hmac [ label = "One-Way Hash", style = "diagonals" ];

rel1 [ label = "Mathematical\nRelationship", shape = "none" ]
rel2 [ label = "Derived\nMathematical\nRelationship", shape = "none" ]

rel1 -> parent_private_key [ weight = "", dir = "back" ];
rel1 -> parent_chain_code [ weight = "", style = "invis" ];
rel1 -> parent_public_key [ weight = "" ];

child_private_key -> rel2 [ ];
child_chain_code -> rel2 [ style = "invis" ];
child_public_key -> rel2 [ dir = "back" ];


//parent_private_key -> parent_public_key [constraint = false, label = "Math Rel" ];
//child_private_key -> child_public_key [constraint = false, minlen = 2];

parent_private_key -> child_private_key;
parent_public_key  -> child_public_key;

parent_public_key -> hmac;
parent_chain_code -> hmac;
parent_private_key -> hmac [ style = "invis" ];
i_norm            -> hmac;

hmac -> child_public_key;
hmac -> child_private_key;
hmac -> child_chain_code;

label = " \nNormal Hierarchical Deterministic (HD) Key Derivation (BIP32)"
}