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118 lines
5.4 KiB
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118 lines
5.4 KiB
Plaintext
<pre>
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BIP: 49
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Layer: Applications
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Title: Derivation scheme for P2WPKH-nested-in-P2SH based accounts
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Author: Daniel Weigl <DanielWeigl@gmx.at>
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Comments-Summary: No comments yet.
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Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0049
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Status: Final
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Type: Standards Track
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Created: 2016-05-19
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License: PD
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</pre>
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==Abstract==
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This BIP defines the derivation scheme for HD wallets using the P2WPKH-nested-in-P2SH ([[bip-0141.mediawiki|BIP 141]]) serialization format for segregated witness transactions.
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==Motivation==
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With the usage of P2WPKH-nested-in-P2SH ([[bip-0141.mediawiki#p2wpkh-nested-in-bip16-p2sh|BIP 141]]) transactions it is necessary to have a common derivation scheme.
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It allows the user to use different HD wallets with the same masterseed and/or a single account seamlessly.
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Thus the user needs to create dedicated segregated witness accounts, which ensures that only wallets compatible with this BIP
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will detect the accounts and handle them appropriately.
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===Considerations===
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Two generally different approaches are possible for current BIP44 capable wallets:
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1) Allow the user to use the same account(s) that they already use, but add segregated witness encoded addresses to it.
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1.1) Use the same public keys as defined in BIP44, but in addition to the normal P2PKH address also derive the P2SH address from it.
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1.2) Use the same account root, but branch off and derive different external and internal chain roots to derive dedicated public keys for the segregated witness addresses.
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2) Create dedicated accounts used only for segregated witness addresses.
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The solutions from point 1 have a common disadvantage: if a user imports/recovers a BIP49-compatible wallet masterseed into/in a non-BIP49-compatible wallet, the account might show up but also it might miss some UTXOs.
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Therefore this BIP uses solution 2, which fails in a more visible way. Either the account shows up or not at all. The user does not have to check his balance after using the same seed in different wallets.
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==Specifications==
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This BIP defines the two needed steps to derive multiple deterministic addresses based on a [[bip-0032.mediawiki|BIP 32]] root account.
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===Public key derivation===
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To derive a public key from the root account, this BIP uses the same account-structure as defined in
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[[bip-0044.mediawiki|BIP 44]], but only uses a different purpose value to indicate the different transaction
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serialization method.
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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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For the `purpose`-path level it uses `49'`. The rest of the levels are used as defined in BIP44.
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===Address derivation===
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To derive the P2SH address from the above calculated public key, we use the encapsulation defined in [[bip-0141.mediawiki#p2wpkh-nested-in-bip16-p2sh|BIP 141]]:
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witness: <signature> <pubkey>
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scriptSig: <0 <20-byte-key-hash>>
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(0x160014{20-byte-key-hash})
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scriptPubKey: HASH160 <20-byte-script-hash> EQUAL
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(0xA914{20-byte-script-hash}87)
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===Extended Key Version===
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When serializing extended keys, this scheme uses alternate version bytes. Extended public keys use <code>0x049d7cb2</code> to produce a "ypub" prefix, and private keys use <code>0x049d7878</code> to produce a "yprv" prefix. Testnet uses <code>0x044a5262</code> "upub" and <code>0x044a4e28</code> "uprv."
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Additional registered version bytes are listed in [[https://github.com/satoshilabs/slips/blob/master/slip-0132.md|SLIP-0132]].
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==Backwards Compatibility==
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This BIP is not backwards compatible by design as described under [[#considerations|considerations]]. An incompatible wallet will not discover accounts at all and the user will notice that something is wrong.
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==Test vectors==
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<pre>
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masterseedWords = abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about
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masterseed = uprv8tXDerPXZ1QsVNjUJWTurs9kA1KGfKUAts74GCkcXtU8GwnH33GDRbNJpEqTvipfCyycARtQJhmdfWf8oKt41X9LL1zeD2pLsWmxEk3VAwd (testnet)
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// Account 0, root = m/49'/1'/0'
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account0Xpriv = uprv91G7gZkzehuMVxDJTYE6tLivdF8e4rvzSu1LFfKw3b2Qx1Aj8vpoFnHdfUZ3hmi9jsvPifmZ24RTN2KhwB8BfMLTVqaBReibyaFFcTP1s9n (testnet)
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account0Xpub = upub5EFU65HtV5TeiSHmZZm7FUffBGy8UKeqp7vw43jYbvZPpoVsgU93oac7Wk3u6moKegAEWtGNF8DehrnHtv21XXEMYRUocHqguyjknFHYfgY (testnet)
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// Account 0, first receiving private key = m/49'/1'/0'/0/0
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account0recvPrivateKey = cULrpoZGXiuC19Uhvykx7NugygA3k86b3hmdCeyvHYQZSxojGyXJ
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account0recvPrivateKeyHex = 0xc9bdb49cfbaedca21c4b1f3a7803c34636b1d7dc55a717132443fc3f4c5867e8
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account0recvPublicKeyHex = 0x03a1af804ac108a8a51782198c2d034b28bf90c8803f5a53f76276fa69a4eae77f
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// Address derivation
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keyhash = HASH160(account0recvPublicKeyHex) = 0x38971f73930f6c141d977ac4fd4a727c854935b3
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scriptSig = <0 <keyhash>> = 0x001438971f73930f6c141d977ac4fd4a727c854935b3
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addressBytes = HASH160(scriptSig) = 0x336caa13e08b96080a32b5d818d59b4ab3b36742
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// addressBytes base58check encoded for testnet
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address = base58check(prefix | addressBytes) = 2Mww8dCYPUpKHofjgcXcBCEGmniw9CoaiD2 (testnet)
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</pre>
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==Reference==
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* [[bip-0016.mediawiki|BIP16 - Pay to Script Hash]]
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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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* [[bip-0044.mediawiki|BIP44 - Multi-Account Hierarchy for Deterministic Wallets]]
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* [[bip-0141.mediawiki|BIP141 - Segregated Witness (Consensus layer)]]
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== Copyright ==
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This document is placed in the public domain.
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