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262 lines
6.0 KiB
262 lines
6.0 KiB
<pre>
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BIP: BIP-0044
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Title: Multi-Account Hierarchy for Deterministic Wallets
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Authors: Marek Palatinus <slush@satoshilabs.com>
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Pavol Rusnak <stick@satoshilabs.com>
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Status: Draft
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Type: Standards Track
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Created: 2014-04-24
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</pre>
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==Abstract==
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This BIP defines a logical hierarchy for deterministic wallets based on an algorithm
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described in BIP-0032 (BIP32 from now on) and purpose scheme described in
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BIP-0043 (BIP43 from now on).
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This BIP is a particular application of BIP43.
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==Motivation==
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The hierarchy proposed in this paper is quite comprehensive. It allows the handling of
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multiple coins, multiple accounts, external and internal chains per account and
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millions of addresses per chain.
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==Path levels==
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We define the following 5 levels in BIP32 path:
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<pre>
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m / purpose' / coin_type' / account' / change / address_index
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</pre>
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Apostrophe in the path indicates that BIP32 hardened derivation is used.
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Each level has a special meaning, described in the chapters below.
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===Purpose===
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Purpose is a constant set to 44' (or 0x8000002C) following the BIP43 recommendation.
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It indicates that the subtree of this node is used according to this specification.
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Hardened derivation is used at this level.
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===Coin type===
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One master node (seed) can be used for unlimited number of independent
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cryptocoins such as Bitcoin, Litecoin or Namecoin. However, sharing the same
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space for various cryptocoins has some disadvantages.
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This level creates a separate subtree for every cryptocoin, avoiding
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reusing addresses across cryptocoins and improving privacy issues.
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Coin type is a constant, set for each cryptocoin. Cryptocoin developers may ask
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for registering unused number for their project.
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The list of already allocated coin types is in the chapter
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"Registered coin types" below.
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Hardened derivation is used at this level.
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===Account===
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This level splits the key space into independent user identities,
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so the wallet never mixes the coins across different accounts.
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Users can use these accounts to organize the funds in the same
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fashion as bank accounts; for donation purposes (where all
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addresses are considered public), for saving purposes,
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for common expenses etc.
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Accounts are numbered from index 0 in sequentially increasing manner.
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This number is used as child index in BIP32 derivation.
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Hardened derivation is used at this level.
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Software should prevent a creation of an account if a previous account does not
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have a transaction history (meaning none of its addresses have been used before).
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Software needs to discover all used accounts after importing the seed from
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an external source. Such an algorithm is described in "Account discovery" chapter.
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===Change===
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Constant 0 is used for external chain and constant 1 for internal chain (also
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known as change addresses). External chain is used for addresses that are meant
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to be visible outside of the wallet (e.g. for receiving payments). Internal
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chain is used for addresses which are not meant to be visible outside of the
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wallet and is used for return transaction change.
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Public derivation is used at this level.
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===Index===
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Addresses are numbered from index 0 in sequentially increasing manner.
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This number is used as child index in BIP32 derivation.
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Public derivation is used at this level.
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==Account discovery==
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When the master seed is imported from an external source the software should
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start to discover the accounts in the following manner:
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# derive the first account's node (index = 0)
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# derive the external chain node of this account
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# scan addresses of the external chain; respect the gap limit described below
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# if no transactions are found on the external chain, stop discovery
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# if there are some transactions, increase the account index and go to step 1
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This algorithm is successful because software should disallow creation of new
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accounts if previous one has no transaction history, as described in chapter
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"Account" above.
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Please note that the algorithm works with the transaction history, not account
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balances, so you can have an account with 0 total coins and the algorithm will
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still continue with discovery.
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===Address gap limit===
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Address gap limit is currently set to 20. If the software hits 20 unused
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addresses in a row, it expects there are no used addresses beyond this point
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and stops searching the address chain.
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Wallet software should warn when the user is trying to exceed the gap limit on
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an external chain by generating a new address.
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==Registered coin types==
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These are the registered coin types for usage in level 2 of BIP44 described in
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chapter "Coin type" above.
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All these constants are used as hardened derivation.
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{|
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!index
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!hexa
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!coin
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|-
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|0
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|0x80000000
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|Bitcoin
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|-
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|1
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|0x80000001
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|Bitcoin Testnet
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|}
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==Examples==
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{|
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!coin
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!account
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!chain
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!address
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!path
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|-
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|Bitcoin
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|first
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|external
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|first
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|m / 44' / 0' / 0' / 0 / 0
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|-
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|Bitcoin
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|first
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|external
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|second
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|m / 44' / 0' / 0' / 0 / 1
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|-
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|Bitcoin
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|first
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|change
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|first
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|m / 44' / 0' / 0' / 1 / 0
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|-
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|Bitcoin
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|first
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|change
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|second
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|m / 44' / 0' / 0' / 1 / 1
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|-
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|Bitcoin
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|second
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|external
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|first
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|m / 44' / 0' / 1' / 0 / 0
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|-
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|Bitcoin
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|second
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|external
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|second
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|m / 44' / 0' / 1' / 0 / 1
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|-
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|Bitcoin
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|second
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|change
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|first
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|m / 44' / 0' / 1' / 1 / 0
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|-
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|Bitcoin
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|second
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|change
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|second
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|m / 44' / 0' / 1' / 1 / 1
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|-
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|Bitcoin Testnet
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|first
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|external
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|first
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|m / 44' / 1' / 0' / 0 / 0
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|-
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|Bitcoin Testnet
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|first
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|external
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|second
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|m / 44' / 1' / 0' / 0 / 1
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|-
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|Bitcoin Testnet
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|first
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|change
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|first
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|m / 44' / 1' / 0' / 1 / 0
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|-
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|Bitcoin Testnet
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|first
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|change
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|second
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|m / 44' / 1' / 0' / 1 / 1
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|-
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|Bitcoin Testnet
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|second
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|external
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|first
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|m / 44' / 1' / 1' / 0 / 0
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|-
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|Bitcoin Testnet
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|second
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|external
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|second
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|m / 44' / 1' / 1' / 0 / 1
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|Bitcoin Testnet
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|second
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|change
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|first
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|m / 44' / 1' / 1' / 1 / 0
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|-
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|Bitcoin Testnet
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|second
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|change
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|second
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|m / 44' / 1' / 1' / 1 / 1
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==Compatible wallets==
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* [[https://mytrezor.com|myTREZOR web wallet]] ([[https://github.com/trezor/webwallet|source]])
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==Reference==
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* [[bip-0032.mediawiki|BIP32 - Hierarchical Deterministic Wallets]]
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* [[bip-0043.mediawiki|BIP43 - Purpose Field for Deterministic Wallets]]
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