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| -rw-r--r-- | doc/descriptors.md | 25 |
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diff --git a/doc/descriptors.md b/doc/descriptors.md index 3b94ec03e4..14380b9c46 100644 --- a/doc/descriptors.md +++ b/doc/descriptors.md @@ -97,6 +97,7 @@ Descriptors consist of several types of expressions. The top level expression is - [WIF](https://en.bitcoin.it/wiki/Wallet_import_format) encoded private keys may be specified instead of the corresponding public key, with the same meaning. - `xpub` encoded extended public key or `xprv` encoded extended private key (as defined in [BIP 32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki)). - Followed by zero or more `/NUM` unhardened and `/NUM'` hardened BIP32 derivation steps. + - No more than one of these derivation steps may be of the form `<NUM;NUM;...;NUM>` (including hardened indicators with either or both `NUM`). If such specifiers are included, the descriptor will be parsed as multiple descriptors where the first descriptor uses all of the first `NUM` in the pair, and the second descriptor uses the second `NUM` in the pair for all `KEY` expressions, and so on. - Optionally followed by a single `/*` or `/*'` final step to denote all (direct) unhardened or hardened children. - The usage of hardened derivation steps requires providing the private key. @@ -256,6 +257,30 @@ Note how the first key is an xprv private key with a specific derivation path, while the other two are public keys. +### Specifying receiving and change descriptors in one descriptor + +Since receiving and change addresses are frequently derived from the same +extended key(s) but with a single derivation index changed, it is convenient +to be able to specify a descriptor that can derive at the two different +indexes. Thus a single tuple of indexes is allowed in each derivation path +following the extended key. When this descriptor is parsed, multiple descriptors +will be produced, the first one will use the first index in the tuple for all +key expressions, the second will use the second index, the third will use the +third index, and so on.. + +For example, a descriptor of the form: + + multi(2,xpub.../<0;1;2>/0/*,xpub.../<2;3;4>/*) + +will expand to the two descriptors + + multi(2,xpub.../0/0/*,xpub.../2/*) + multi(2,xpub.../1/0/*,xpub.../3/*) + multi(2,xpub.../2/0/*,xpub.../4*) + +When this tuple contains only two elements, wallet implementations can use the +first descriptor for receiving addresses and the second descriptor for change addresses. + ### Compatibility with old wallets In order to easily represent the sets of scripts currently supported by |