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Update documentation to incude origin information

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Pieter Wuille 2018-10-12 16:17:59 -07:00
parent ff37459abc
commit 8afb166875
1 changed files with 43 additions and 9 deletions
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doc/descriptors.md
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@ -34,6 +34,7 @@ Output descriptors currently support:
- `sh(wsh(multi(1,03f28773c2d975288bc7d1d205c3748651b075fbc6610e58cddeeddf8f19405aa8,03499fdf9e895e719cfd64e67f07d38e3226aa7b63678949e6e49b241a60e823e4,02d7924d4f7d43ea965a465ae3095ff41131e5946f3c85f79e44adbcf8e27e080e)))` describes a P2SH-P2WSH *1-of-3* multisig output with keys in the specified order.
- `pk(xpub661MyMwAqRbcFtXgS5sYJABqqG9YLmC4Q1Rdap9gSE8NqtwybGhePY2gZ29ESFjqJoCu1Rupje8YtGqsefD265TMg7usUDFdp6W1EGMcet8)` describes a P2PK output with the public key of the specified xpub.
- `pkh(xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw/1'/2)` describes a P2PKH output with child key *1'/2* of the specified xpub.
- `pkh([d34db33f/44'/0'/0']xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL/1/*)` describes a set of P2PKH outputs, but additionally specifies that the specified xpub is a child of a master with fingerprint `d34db33f`, and derived using path `44'/0'/0'`.
- `wsh(multi(1,xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB/1/0/*,xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH/0/0/*))` describes a set of *1-of-2* P2WSH multisig outputs where the first multisig key is the *1/0/`i`* child of the first specified xpub and the second multisig key is the *0/0/`i`* child of the second specified xpub, and `i` is any number in a configurable range (`0-1000` by default).
## Reference
@ -52,14 +53,20 @@ Descriptors consist of several types of expressions. The top level expression is
- `raw(HEX)` (top level only): the script whose hex encoding is HEX.
`KEY` expressions:
- Hex encoded public keys (66 characters starting with `02` or `03`, or 130 characters starting with `04`).
- Optionally, key origin information, consisting of:
- An open bracket `[`
- Exactly 8 hex characters for the fingerprint of the key where the derivation starts (see BIP32 for details)
- Followed by zero or more `/NUM` or `/NUM'` path elements to indicate unhardened or hardened derivation steps between the fingerprint and the key or xpub/xprv root that follows
- A closing bracket `]`
- Followed by the actual key, which is either:
- Hex encoded public keys (66 characters starting with `02` or `03`, or 130 characters starting with `04`).
- Inside `wpkh` and `wsh`, only compressed public keys are permitted.
- [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 private key (as defined in [BIP 32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki)).
- [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 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.
- 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.
- Instead of a `'`, the suffix `h` can be used to denote hardened derivation.
- Anywhere a `'` suffix is permitted to denote hardened derivation, the suffix `h` can be used instead.
`ADDR` expressions are any type of supported address:
- P2PKH addresses (base58, of the form `1...`). Note that P2PKH addresses in descriptors cannot be used for P2PK outputs (use the `pk` function instead).
@ -116,6 +123,33 @@ Whenever a public key is described using a hardened derivation step, the
script cannot be computed without access to the corresponding private
key.
### Key origin identification
In order to describe scripts whose signing keys reside on another device,
it may be necessary to identify the master key and derivation path an
xpub was derived with.
For example, when following BIP44, it would be useful to describe a
change chain directly as `xpub.../44'/0'/0'/1/*` where `xpub...`
corresponds with the master key `m`. Unfortunately, since there are
hardened derivation steps that follow the xpub, this descriptor does not
let you compute scripts without access to the corresponding private keys.
Instead, it should be written as `xpub.../1/*`, where xpub corresponds to
`m/44'/0'/0'`.
When interacting with a hardware device, it may be necessary to include
the entire path from the master down. BIP174 standardizes this by
providing the master key *fingerprint* (first 32 bit of the Hash160 of
the master pubkey), plus all derivation steps. To support constructing
these, we permit providing this key origin information inside the
descriptor language, even though it does not affect the actual
scriptPubKeys it refers to.
Every public key can be prefixed by an 8-character hexadecimal
fingerprint plus optional derivation steps (hardened and unhardened)
surrounded by brackets, identifying the master and derivation path the key or xpub
that follows was derived with.
### Including private keys
Often it is useful to communicate a description of scripts along with the