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diff --git a/README.mediawiki b/README.mediawiki index d8bcae6..eaafbef 100644 --- a/README.mediawiki +++ b/README.mediawiki @@ -434,6 +434,13 @@ Those proposing changes should consider that ultimately consent may rest with th | Ethan Kosakovsky | Informational | Draft +|- +| [[bip-0086.mediawiki|86]] +| Applications +| Key Derivation for Single Key P2TR Outputs +| Andrew Chow +| Standard +| Draft |- style="background-color: #ffffcf" | [[bip-0087.mediawiki|87]] | Applications diff --git a/bip-0086.mediawiki b/bip-0086.mediawiki new file mode 100644 index 0000000..f724884 --- /dev/null +++ b/bip-0086.mediawiki @@ -0,0 +1,128 @@ +<pre> + BIP: 86 + Layer: Applications + Title: Key Derivation for Single Key P2TR Outputs + Author: Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0086 + Status: Draft + Type: Standards Track + Created: 2021-06-22 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document suggests a derivation scheme for HD wallets whose keys are involved in single key +P2TR ([[bip-0341.mediawiki|BIP 341]]) outputs as the Taproot internal key. + +===Copyright=== + +This BIP is licensed under the 2-clause BSD license. + +==Motivation== + +With the usage of single key P2TR transactions, it is useful to have a common derivation scheme so +that HD wallets that only have a backup of the HD seed can be likely to recover single key Taproot +outputs. Although there are now solutions which obviate the need for fixed derivation paths for +specific script types, many software wallets and hardware signers still use seed backups which +lack derivation path and script information. Thus we largely use the same approach used in BIPs +[[bip-0049.mediawiki|49]] and [[bip-0084.mediawiki|84]] for ease of implementation. + +==Specifications== + +This BIP defines the two needed steps to derive multiple deterministic addresses based on a +[[bip-0032.mediawiki|BIP 32]] master private key. + +===Public key derivation=== + +To derive a public key from the root account, this BIP uses the same account-structure as +defined in BIPs [[bip-0044.mediawiki|44]], [[bip-0049.mediawiki|49]], and [[bip-0084.mediawiki|84]], +but with a different purpose value for the script type. + +<pre> +m / purpose' / coin_type' / account' / change / address_index +</pre> + +For the <tt>purpose</tt>-path level it uses <tt>86'</tt>. +The rest of the levels are used as defined in BIPs 44, 49, and 84. + +A key derived with this derivation path pattern will be referred to as <tt>derived_key</tt> further +in this document. + +===Address derivation=== + + +[[bip-0341.mediawiki#cite_ref-22-0|BIP 341]] states: "If the spending conditions do not require a +script path, the output key should commit to an unspendable script path instead of having no +script path. This can be achieved by computing the output key point as +''Q = P + int(hash<sub>TapTweak</sub>(bytes(P)))G''." Thus: + +<pre> +internal_key: lift_x(derived_key) +32_byte_output_key: internal_key + int(HashTapTweak(bytes(internal_key)))G +</pre> + +In a transaction, the scripts and witnesses are as defined in +[[bip-0341.mediawiki#specification|BIP 341]]: + +<pre> +witness: <signature> +scriptSig: (empty) +scriptPubKey: 1 <32_byte_output_key> + (0x5120{32_byte_output_key}) +</pre> + +==Backwards Compatibility== + +This BIP is not backwards compatible by design. +An incompatible wallet will not discover these accounts at all and the user will notice that +something is wrong. + +However this BIP uses the same method used in BIPs 44, 49, and 84, so it should not be difficult +to implement. + +==Test vectors== + +<pre> +mnemonic = abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about +rootpriv = xprv9s21ZrQH143K3GJpoapnV8SFfukcVBSfeCficPSGfubmSFDxo1kuHnLisriDvSnRRuL2Qrg5ggqHKNVpxR86QEC8w35uxmGoggxtQTPvfUu +rootpub = xpub661MyMwAqRbcFkPHucMnrGNzDwb6teAX1RbKQmqtEF8kK3Z7LZ59qafCjB9eCRLiTVG3uxBxgKvRgbubRhqSKXnGGb1aoaqLrpMBDrVxga8 + +// Account 0, root = m/86'/0'/0' +xprv = xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk +xpub = xpub6BgBgsespWvERF3LHQu6CnqdvfEvtMcQjYrcRzx53QJjSxarj2afYWcLteoGVky7D3UKDP9QyrLprQ3VCECoY49yfdDEHGCtMMj92pReUsQ + +// Account 0, first receiving address = m/86'/0'/0'/0/0 +xprv = xprvA449goEeU9okwCzzZaxiy475EQGQzBkc65su82nXEvcwzfSskb2hAt2WymrjyRL6kpbVTGL3cKtp9herYXSjjQ1j4stsXXiRF7kXkCacK3T +xpub = xpub6H3W6JmYJXN49h5TfcVjLC3onS6uPeUTTJoVvRC8oG9vsTn2J8LwigLzq5tHbrwAzH9DGo6ThGUdWsqce8dGfwHVBxSbixjDADGGdzF7t2B +internal_key = cc8a4bc64d897bddc5fbc2f670f7a8ba0b386779106cf1223c6fc5d7cd6fc115 +output_key = a60869f0dbcf1dc659c9cecbaf8050135ea9e8cdc487053f1dc6880949dc684c +scriptPubKey = 5120a60869f0dbcf1dc659c9cecbaf8050135ea9e8cdc487053f1dc6880949dc684c +address = bc1p5cyxnuxmeuwuvkwfem96lqzszd02n6xdcjrs20cac6yqjjwudpxqkedrcr + +// Account 0, second receiving address = m/86'/0'/0'/0/1 +xprv = xprvA449goEeU9okyiF1LmKiDaTgeXvmh87DVyRd35VPbsSop8n8uALpbtrUhUXByPFKK7C2yuqrB1FrhiDkEMC4RGmA5KTwsE1aB5jRu9zHsuQ +xpub = xpub6H3W6JmYJXN4CCKUSnriaiQRCZmG6aq4sCMDqTu1ACyngw7HShf59hAxYjXgKDuuHThVEUzdHrc3aXCr9kfvQvZPit5dnD3K9xVRBzjK3rX +internal_key = 83dfe85a3151d2517290da461fe2815591ef69f2b18a2ce63f01697a8b313145 +output_key = a82f29944d65b86ae6b5e5cc75e294ead6c59391a1edc5e016e3498c67fc7bbb +scriptPubKey = 5120a82f29944d65b86ae6b5e5cc75e294ead6c59391a1edc5e016e3498c67fc7bbb +address = bc1p4qhjn9zdvkux4e44uhx8tc55attvtyu358kutcqkudyccelu0was9fqzwh + +// Account 0, first change address = m/86'/0'/0'/1/0 +xprv = xprvA3Ln3Gt3aphvUgzgEDT8vE2cYqb4PjFfpmbiFKphxLg1FjXQpkAk5M1ZKDY15bmCAHA35jTiawbFuwGtbDZogKF1WfjwxML4gK7WfYW5JRP +xpub = xpub6GL8SnQwRCGDhB59LEz9HMyM6sRYoByXBzXK3iEKWgCz8XrZNHUzd9L3AUBELW5NzA7dEFvMas1F84TuPH3xqdUA5tumaGWFgihJzWytXe3 +internal_key = 399f1b2f4393f29a18c937859c5dd8a77350103157eb880f02e8c08214277cef +output_key = 882d74e5d0572d5a816cef0041a96b6c1de832f6f9676d9605c44d5e9a97d3dc +scriptPubKey = 5120882d74e5d0572d5a816cef0041a96b6c1de832f6f9676d9605c44d5e9a97d3dc +address = bc1p3qkhfews2uk44qtvauqyr2ttdsw7svhkl9nkm9s9c3x4ax5h60wqwruhk7 +</pre> + +==Reference== + +* [[bip-0032.mediawiki|BIP32 - Hierarchical Deterministic Wallets]] +* [[bip-0043.mediawiki|BIP43 - Purpose Field for Deterministic Wallets]] +* [[bip-0044.mediawiki|BIP44 - Multi-Account Hierarchy for Deterministic Wallets]] +* [[bip-0049.mediawiki|BIP49 - Derivation scheme for P2WPKH-nested-in-P2SH based accounts]] +* [[bip-0084.mediawiki|BIP84 - Derivation scheme for P2WPKH based accounts]] +* [[bip-0341.mediawiki|BIP341 - Taproot: SegWit version 1 spending rules]] |