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53 lines
1.8 KiB
Markdown
53 lines
1.8 KiB
Markdown
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# Purpose48 derivation scheme
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Per [BIP-43], the first level of the derivation path is used as a "purpose". The purpose
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number is usually selected to match the BIP number: e.g., BIP-49 uses purpose `49'`.
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There is no officially proposed **BIP-48** standard. Despite that, a de-facto standard
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for the purpose `48'` exists in the wild and is implemented by several HD wallets, most
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notably [Electrum]. This standard was never before formally
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specified, and this document aims to rectify the situation.
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## Motivation
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Purpose48 is intended for multisig scenarios. It allows using multiple script types from
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a single logical account or root key, while keeping multisig keys separate from
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single-sig keys.
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## Specification
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The following BIP-32 path levels are defined:
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```
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m / 48' / coin_type' / account' / script_type' / change / address_index
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```
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Meaning of all fields except `script_type` is defined in [BIP-44]
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`script_type` can have the following values:
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* `0`: raw [BIP-11] (p2ms) multisig
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* `1`: p2sh-wrapped segwit multisig (p2wsh-p2sh)
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* `2`: native segwit multisig (p2wsh)
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The path derivation is hardened up to and including the `script_type` field.
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## Trezor implementation
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`script_type` value `0` corresponds to `SPENDMULTISIG`/`PAYTOMULTISIG`.
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Value `1` corresponds to `SPENDP2SHWITNESS`/`PAYTOP2SHWITNESS`.
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Value `2` corresponds to `SPENDWITNESS`/`PAYTOWITNESS`.
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## References
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Electrum implementation: https://github.com/spesmilo/electrum/blob/9931df9f254e49eb929723be62af61971b3032c8/electrum/keystore.py#L862-L889
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Trezor implementation: TBD
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[Electrum]: https://electrum.org/
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[BIP-11]: https://github.com/bitcoin/bips/blob/master/bip-0011.mediawiki
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[BIP-43]: https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki
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[BIP-44]: https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki
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