Bitcoin Improvement Proposals : BIP 0081

  BIP: 81
  Title: Hierarchy for Colored Voting Pool Deterministic Multisig Wallets
  Author: Justus Ranvier <[email protected]>
          Jimmy Song <[email protected]>
  Status: Deferred
  Type: Informational
  Created: 2014-08-11

Table of Contents


This BIP defines a logical hierarchy for colored coin voting pool deterministic multisig wallets based on an algorithm described in BIP-0032 (BIP32 from now on) and purpose scheme described in BIP-0043 (BIP43 from now on).

This BIP is a particular application of BIP43 and is based on BIP44.


The hierarchy proposed in this paper allows the handling of multiple color definitions from a single seed.

Path levels

We define the following 8 levels in BIP32 path:

m / purpose' / series' / (5 color definition levels) / address_index

Apostrophe in the path indicates that BIP32 hardened derivation is used.

Each level has a special meaning, described in the chapters below.


Purpose is a constant set following the BIP43 recommendation to: the ASCII value of "81" with the most signifigant bit set to indicate hardened derivation (0x80000051). It indicates that the subtree of this node is used according to this specification.

Hardened derivation is used at this level.

Color Definition

Index values which can be applied to a BIP32 node are limited to 4 bytes (32 bits).

Since this is not sufficient to identify color definitions without a risk of collision, multiple levels are used.

Color definitions are first shortened to 20 bytes using the Bitcoin hash160 function.

The resulting 20 bytes are split into five groups in little endian format, and where each group is used as the seed for the five levels of color definition levels

Public derivation is used at these levels, even when the index exceeds 2^31.


Public/private keypairs are numbered from index 0 in sequentially increasing manner. This number is used as child index in BIP32 derivation.

Public keys obtained at this level of the heirarchy are used to construct multisig deposit scripts, using a schema that is shared between the members as an out-of-band contract.

Public derivation is used at this level.

Compatible wallets

  • btcwallet is the reference Bitcoin wallet for voting pools.


This document is placed in the public domain.