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diff --git a/README.mediawiki b/README.mediawiki index f3dbcda..d3143d3 100644 --- a/README.mediawiki +++ b/README.mediawiki @@ -1050,6 +1050,55 @@ Those proposing changes should consider that ultimately consent may rest with th | Andrew Chow | Standard | Draft +|- +| [[bip-0380.mediawiki|380]] +| Applications +| Output Script Descriptors General Operation +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0381.mediawiki|381]] +| Applications +| Non-Segwit Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0382.mediawiki|382]] +| Applications +| Segwit Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0383.mediawiki|383]] +| Applications +| Multisig Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0384.mediawiki|384]] +| Applications +| combo() Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0385.mediawiki|385]] +| Applications +| raw() and addr() Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft +|- +| [[bip-0386.mediawiki|386]] +| Applications +| tr() Output Script Descriptors +| Pieter Wuille, Andrew Chow +| Informational +| Draft |} <!-- IMPORTANT! See the instructions at the top of this page, do NOT JUST add BIPs here! --> diff --git a/bip-0380.mediawiki b/bip-0380.mediawiki new file mode 100644 index 0000000..d57bbc6 --- /dev/null +++ b/bip-0380.mediawiki @@ -0,0 +1,277 @@ +<pre> + BIP: 380 + Layer: Applications + Title: Output Script Descriptors General Operation + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0380 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +Output Script Descriptors are a simple language which can be used to describe collections of output scripts. +There can be many different descriptor fragments and functions. +This document describes the general syntax for descriptors, descriptor checksums, and common expressions. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +Bitcoin wallets traditionally have stored a set of keys which are later serialized and mutated to produce the output scripts that the wallet watches and the addresses it provides to users. +Typically backups have consisted of solely the private keys, nowadays primarily in the form of BIP 39 mnemonics. +However this backup solution is insuffient, especially since the introduction of Segregated Witness which added new output types. +Given just the private keys, it is not possible for restored wallets to know which kinds of output scripts and addresses to produce. +This has lead to incompatibilities between wallets when restoring a backup or exporting data for a watch only wallet. + +Further complicating matters are BIP 32 derivation paths. +Although BIPs 44, 49, and 84 have specified standard BIP 32 derivation paths for different output scripts and addresses, not all wallets support them nor use those derivation paths. +The lack of derivation path information in these backups and exports leads to further incompatibilities between wallets. + +Current solutions to these issues have not been generic and can be viewed as being layer violations. +Solutions such as introducing different version bytes for extended key serialization both are a layer violation (key derivation should be separate from script type meaning) and specific only to a particular derivation path and script type. + +Output Script Descriptors introduces a generic solution to these issues. +Script types are specified explicitly through the use of Script Expressions. +Key derivation paths are specified explicitly in Key Expressions. +These allow for creating wallet backups and exports which specify the exact scripts, subscripts (redeemScript, witnessScript, etc.), and keys to produce. +With the general structure specified in this BIP, new Script Expressions can be introduced as new script types are added. +Lastly, the use of common terminology and existing standards allow for Output Script Descriptors to be engineer readable so that the results can be understood at a glance. + +==Specification== + +Descriptors consist of several types of expressions. +The top level expression is a <tt>SCRIPT</tt>. +This expression may be followed by <tt>#CHECKSUM</tt>, where <tt>CHECKSUM</tt> is an 8 character alphanumeric descriptor checksum. + +===Script Expressions=== + +Script Expressions (denoted <tt>SCRIPT</tt>) are expressions which correspond directly with a Bitcoin script. +These expressions are written as functions and take arguments. +Such expressions have a script template which is filled with the arguments correspondingly. +Expressions are written with a human readable identifier string with the arguments enclosed with parentheses. +The identifier string should be alphanumeric and may include underscores. + +The arguments to a script expression are defined by that expression itself. +They could be a script expression, a key expression, or some other expression entirely. + +===Key Expressions=== + +A common expression used as an argument to script expressions are key expressions (denoted <tt>KEY</tt>). +These represent a public or private key and, optionally, information about the origin of that key. +Key expressions can only be used as arguments to script expressions. + +Key expressions consist of: +* Optionally, key origin information, consisting of: +** An open bracket <tt>[</tt> +** Exactly 8 hex characters for the fingerprint of the key where the derivation starts (see BIP 32 for details) +** Followed by zero or more <tt>/NUM</tt> or <tt>/NUMh</tt> path elements to indicate the unhardened or hardened derivation steps between the fingerprint and the key that follows. +** A closing bracket <tt>]</tt> +* Followed by the actual key, which is either: +** A hex encoded public key, which depending the script expression, may be either: +*** 66 hex character string beginning with <tt>02</tt> or <tt>03</tt> representing a compressed public key +*** 130 hex character string beginning with <tt>04</tt> representing an uncompressed public key +** A [[https://en.bitcoin.it/wiki/Wallet_import_format|WIF]] encoded private key +** <tt>xpub</tt> encoded extended public key or <tt>xprv</tt> encoded extended private key (as defined in BIP 32) +*** Followed by zero or more <tt>/NUM</tt> or <tt>/NUMh</tt> path elements indicating BIP 32 derivation steps to be taken after the given extended key. +*** Optionally followed by a single <tt>/*</tt> or <tt>/*h</tt> final step to denote all direct unhardened or hardened children. + +If the <tt>KEY</tt> is a BIP 32 extended key, before output scripts can be created, child keys must be derived using the derivation information that follows the extended key. +When the final step is <tt>/*</tt> or <tt>/*'</tt>, an output script will be produced for every child key index. +The derived key must be not be serialized as an uncompressed public key. +Script Expressions may have further requirements on how derived public keys are serialized for script creation. + +In the above specification, the hardened indicator <tt>h</tt> may be replaced with alternative hardened indicators of <tt>H</tt> or <tt>'</tt>. + +====Normalization of Key Expressions with Hardened Derivation==== + +When a descriptor is exported without private keys, it is necessary to do additional derivation to remove any intermediate hardened derivation steps for the exported descriptor to be useful. +The exporter should derive the extended public key at the last hardened derivation step and use that extended public key as the key in the descriptor. +The derivation steps that were taken to get to that key must be added to the previous key origin information. +If there is no key origin information, then one must be added for the newly derived extended public key. +If the final derivation is hardened, then it is not necessary to do additional derivation. + +===Character Set=== + +The expressions used in descriptors must only contain characters within this character set so that the descriptor checksum will work. + +The allowed characters are: +<pre> +0123456789()[],'/*abcdefgh@:$%{} +IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ +ijklmnopqrstuvwxyzABCDEFGH`#"\<space> +</pre> +Note that <tt><space></tt> on the last line is a space character. + +This character set is written as 3 groups of 32 characters in this specific order so that the checksum below can identify more errors. +The first group are the most common "unprotected" characters (i.e. things such as hex and keypaths that do not already have their own checksums). +Case errors cause an offset that is a multiple of 32 while as many alphabetic characters are in the same group while following the previous restrictions. + +===Checksum=== + +Following the top level script expression is a single octothorpe (<tt>#</tt>) followed by the 8 character checksum. +The checksum is an error correcting checksum similar to bech32. + +The checksum has the following properties: +* Mistakes in a descriptor string are measured in "symbol errors". The higher the number of symbol errors, the harder it is to detect: +** An error substituting a character from <tt>0123456789()[],'/*abcdefgh@:$%{}</tt> for another in that set always counts as 1 symbol error. +*** Note that hex encoded keys are covered by these characters. Extended keys (<tt>xpub</tt> and <tt>xprv</tt>) use other characters too, but also have their own checksum mechanism. +*** <tt>SCRIPT</tt> expression function names use other characters, but mistakes in these would generally result in an unparsable descriptor. +** A case error always counts as 1 symbol error. +** Any other 1 character substitution error counts as 1 or 2 symbol errors. +* Any 1 symbol error is always detected. +* Any 2 or 3 symbol error in a descriptor of up to 49154 characters is always detected. +* Any 4 symbol error in a descriptor of up to 507 characters is always detected. +* Any 5 symbol error in a descriptor of up to 77 characters is always detected. +* Is optimized to minimize the chance of a 5 symbol error in a descriptor up to 387 characters is undetected +* Random errors have a chance of 1 in 2<super>40</super> of being undetected. + +The checksum itself uses the same character set as bech32: <tt>qpzry9x8gf2tvdw0s3jn54khce6mua7l</tt> + +Valid descriptor strings with a checksum must pass the criteria for validity specified by the Python3 code snippet below. +The function <tt>descsum_check</tt> must return true when its argument <tt>s</tt> is a descriptor consisting in the form <tt>SCRIPT#CHECKSUM</tt>. + +<pre> +INPUT_CHARSET = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ " +CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l" +GENERATOR = [0xf5dee51989, 0xa9fdca3312, 0x1bab10e32d, 0x3706b1677a, 0x644d626ffd] + +def descsum_polymod(symbols): + """Internal function that computes the descriptor checksum.""" + chk = 1 + for value in symbols: + top = chk >> 35 + chk = (chk & 0x7ffffffff) << 5 ^ value + for i in range(5): + chk ^= GENERATOR[i] if ((top >> i) & 1) else 0 + return chk + +def descsum_expand(s): + """Internal function that does the character to symbol expansion""" + groups = [] + symbols = [] + for c in s: + if not c in INPUT_CHARSET: + return None + v = INPUT_CHARSET.find(c) + symbols.append(v & 31) + groups.append(v >> 5) + if len(groups) == 3: + symbols.append(groups[0] * 9 + groups[1] * 3 + groups[2]) + groups = [] + if len(groups) == 1: + symbols.append(groups[0]) + elif len(groups) == 2: + symbols.append(groups[0] * 3 + groups[1]) + return symbols + +def descsum_check(s): + """Verify that the checksum is correct in a descriptor""" + if s[-9] != '#': + return False + if not all(x in CHECKSUM_CHARSET for x in s[-8:]): + return False + symbols = descsum_expand(s[:-9]) + [CHECKSUM_CHARSET.find(x) for x in s[-8:]] + return descsum_polymod(symbols) == 1 +</pre> + +This implements a BCH code that has the properties described above. +The entire descriptor string is first processed into an array of symbols. +The symbol for each character is its position within its group. +After every 3rd symbol, a 4th symbol is inserted which represents the group numbers combined together. +This means that a change that only affects the position within a group, or only a group number change, will only affect a single symbol. + +To construct a valid checksum given a script expression, the code below can be used: + +<pre> +def descsum_create(s): + """Add a checksum to a descriptor without""" + symbols = descsum_expand(s) + [0, 0, 0, 0, 0, 0, 0, 0] + checksum = descsum_polymod(symbols) ^ 1 + return s + '#' + ''.join(CHECKSUM_CHARSET[(checksum >> (5 * (7 - i))) & 31] for i in range(8)) + +</pre> + +==Backwards Compatibility== + +Output script descriptors are an entirely new language which is not compatible with any existing software. +However many components of the expressions reuse encodings and serializations defined by previous BIPs. + +Output script descriptors are designed for future extension with further fragment types and new script expressions. +These will be specified in additional BIPs. + +==Reference Implemntation== + +Descriptors have been implemented in Bitcoin Core since version 0.17. + +==Appendix A: Index of Expressions== + +Future BIPs may specify additional types of expressions. +All available expression types are listed in this table. + +{| +! Name +! Denoted As +! BIP +|- +| Script +| <tt>SCRIPT</tt> +| 380 +|- +| Key +| <tt>KEY</tt> +| 380 +|- +| Tree +| <tt>TREE</tt> +| [[bip-0386.mediawiki|386]] +|} + +==Appendix B: Index of Script Expressions== + +Script expressions will be specified in additional BIPs. +This Table lists all available Script expressions and the BIPs specifying them. + +{| +! Expression +! BIP +|- +| <tt>pk(KEY)</tt> +| [[bip-0381.mediawiki|381]] +|- +| <tt>pkh(KEY)</tt> +| [[bip-0381.mediawiki|381]] +|- +| <tt>sh(SCRIPT)</tt> +| [[bip-0381.mediawiki|381]] +|- +| <tt>wpkh(KEY)</tt> +| [[bip-0382.mediawiki|382]] +|- +| <tt>wsh(SCRIPT)</tt> +| [[bip-0382.mediawiki|382]] +|- +| <tt>multi(NUM, KEY, ..., KEY)</tt> +| [[bip-0383.mediawiki|383]] +|- +| <tt>sortedmulti(NUM, KEY, ..., KEY)</tt> +| [[bip-0383.mediawiki|383]] +|- +| <tt>combo(KEY)</tt> +| [[bip-0384.mediawiki|384]] +|- +| <tt>raw(HEX)</tt> +| [[bip-0385.mediawiki|385]] +|- +| <tt>addr(ADDR)</tt> +| [[bip-0385.mediawiki|385]] +|- +| <tt>tr(KEY)</tt>, <tt>tr(KEY, TREE)</tt> +| [[bip-0386.mediawiki|386]] +|} diff --git a/bip-0381.mediawiki b/bip-0381.mediawiki new file mode 100644 index 0000000..8d7e391 --- /dev/null +++ b/bip-0381.mediawiki @@ -0,0 +1,83 @@ +<pre> + BIP: 381 + Layer: Applications + Title: Non-Segwit Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0381 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>pk()</tt>, <tt>pkh()</tt>, and <tt>sh()</tt> output script descriptors. +<tt>pk()</tt> descriptors take a key and produces a P2PK output script. +<tt>pkh()</tt> descriptors take a key and produces a P2PKH output script. +<tt>sh()</tt> descriptors take a script and produces a P2SH output script. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +Prior to the activation of Segregated Witness, there were 3 main standard output script formats: P2PK, P2PKH, and P2SH. +These expressions allow specifying those formats as a descriptor. + +==Specification== + +Three new script expressions are defined: <tt>pk()</tt>, <tt>pkh()</tt>, and <tt>sh()</tt>. + +===<tt>pk()</tt>=== + +The <tt>pk(KEY)</tt> expression can be used in any context or level of a descriptor. +It takes a single key expression as an argument and produces a P2PK output script. +Depending on the higher level descriptors, there may be restrictions on the type of public keys that can be included. +Such restrictions will be specified by those descriptors. + +The output script produced is: +<pre> +<KEY> OP_CHECKSIG +</pre> + +===<tt>pkh()</tt>=== + +The <tt>pkh(KEY)</tt> expression can be used as a top level expression, or inside of either a <tt>sh()</tt> or <tt>wsh()</tt> descriptor. +It takes a single key expression as an argument and produces a P2PKH output script. +Depending on the higher level descriptors, there may be restrictions on the type of public keys that can be included. +Such restrictions will be specified by those descriptors. + +The output script produced is: +<pre> +OP_DUP OP_HASH160 <KEY_hash160> OP_EQUALVERIFY OP_CHECKSIG +</pre> + +===<tt>sh()</tt>=== + +The <tt>sh(SCRIPT)</tt> expression can only be used as a top level expression. +It takes a single script expression as an argument and produces a P2SH output script. +<tt>sh()</tt> expressions also create a redeemScript which is required in order to spend outputs which use its output script. +This redeemScript is the output script produced by the <tt>SCRIPT</tt> argument to <tt>sh()</tt>. + +The output script produced is: +<pre> +OP_HASH160 <SCRIPT_hash160> OP_EQUAL +</pre> + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>pk()</tt>, <tt>pkh()</tt>, and <tt>sh()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As these are a wholly new descriptors, they are not compatible with any implementation. +However the scripts produced are standard scripts so existing software are likely to be familiar with them. + +==Reference Implemntation== + +<tt>pk()</tt>, <tt>pkh()</tt>, and <tt>sh()</tt> descriptors have been implemented in Bitcoin Core since version 0.17. diff --git a/bip-0382.mediawiki b/bip-0382.mediawiki new file mode 100644 index 0000000..0508d2b --- /dev/null +++ b/bip-0382.mediawiki @@ -0,0 +1,70 @@ +<pre> + BIP: 382 + Layer: Applications + Title: Segwit Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0382 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>wpkh()</tt>, and <tt>wsh()</tt> output script descriptors. +<tt>wpkh()</tt> descriptors take a key and produces a P2WPKH output script. +<tt>wsh()</tt> descriptors take a script and produces a P2WSH output script. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +Segregated Witness added 2 additional standard output script formats: P2WPKH and P2WSH. +These expressions allow specifying those formats as a descriptor. + +==Specification== + +Two new script expressions are defined: <tt>wpkh()</tt>, and <tt>wsh()</tt>. + +===<tt>wpkh()</tt>=== + +The <tt>wpkh(KEY)</tt> expression can be used as a top level expression, or inside of a <tt>sh()</tt> descriptor. +It takes a single key expression as an argument and produces a P2WPKH output script. +Only keys which are/has compressed public keys can be contained in a <tt>wpkh()</tt> expression. + +The output script produced is: +<pre> +OP_0 <KEY_hash160> +</pre> + +===<tt>wsh()</tt>=== + +The <tt>wsh(SCRIPT)</tt> expression can be used as a top level expression, or inside of a <tt>sh()</tt> descriptor. +It takes a single script expression as an argument and produces a P2WSH output script. +<tt>wsh()</tt> expressions also create a witnessScript which is required in order to spend outputs which use its output script. +This redeemScript is the output script produced by the <tt>SCRIPT</tt> argument to <tt>wsh()</tt>. +Any key expression found in any script expression contained by a <tt>wsh()</tt> expression must only produce compressed public keys. + +The output script produced is: +<pre> +OP_0 <SCRIPT_sha256> +</pre> + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>wpkh()</tt>, and <tt>wsh()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As these are a wholly new descriptors, they are not compatible with any implementation. +However the scripts produced are standard scripts so existing software are likely to be familiar with them. + +==Reference Implemntation== + +<tt>wpkh()</tt>, and <tt>wsh()</tt> descriptors have been implemented in Bitcoin Core since version 0.17. diff --git a/bip-0383.mediawiki b/bip-0383.mediawiki new file mode 100644 index 0000000..6b74950 --- /dev/null +++ b/bip-0383.mediawiki @@ -0,0 +1,78 @@ +<pre> + BIP: 383 + Layer: Applications + Title: Multisig Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0383 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>multi()</tt>, and <tt>sortedmulti()</tt> output script descriptors. +Both functions take a threshold and one or more public keys and produce a multisig output script. +<tt>multi()</tt> specifies the public keys in the output script in the order given in the descriptor while <tt>sortedmulti()</tt> sorts the public keys lexicographically when the output script is produced. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +The most common complex script used in Bitcoin is a threshold multisig. +These expressions allow specifying multisig scripts as a descriptor. + +==Specification== + +Two new script expressions are defined: <tt>multi()</tt>, and <tt>sortedmulti()</tt>. +Both expressions produce the scripts of the same template and take the same arguments. +They are written as <tt>multi(k,KEY_1,KEY_2,...,KEY_n)</tt>. +<tt>k</tt> is the threshold - the number of keys that must sign the input for the script to be valid. +<tt>KEY_1,KEY_2,...,KEY_n</tt> are the key expressions for the multisig. <tt>k</tt> must be less than or equal to <tt>n</tt>. + +<tt>multi()</tt> and <tt>sortedmulti()</tt> expressions can be used as a top level expression, or inside of either a <tt>sh()</tt> or <tt>wsh()</tt> descriptor. +Depending on the higher level descriptors, there may be restrictions on the type of public keys that can be included. + +Depending on the higher level descriptors, there are also restrictions on the number of keys that can be present, i.e. the maximum value of <tt>n</tt>. +When used at the top level, there can only be at most 3 keys. +When used inside of a <tt>sh()</tt> expression, there can only be most 15 compressed public keys (this is limited by the P2SH script limit). +Otherwise the maximum number of keys is 20. + +The output script produced also depends on the value of <tt>k</tt>. If <tt>k</tt> is less than or equal to 16: +<pre> +OP_k KEY_1 KEY_2 ... KEY_n OP_CHECKMULTISIG +</pre> + +if <tt>k</tt> is greater than 16: +<pre> +k KEY_1 KEY_2 ... KEY_n OP_CHECKMULTISIG +</pre> + +===<tt>sortedmulti()</tt>=== + +The only change for <tt>sortedmulti()</tt> is that the keys are sorted lexicographically prior to the creation of the output script. +This sorting is on the keys that are to be put into the output script, i.e. after all extended keys are derived. + +===Multiple Extended Keys</tt>=== + +When one or more the key expressions in a <tt>multi()</tt> or <tt>sortedmulti()</tt> expression are extended keys, the derived keys use the same child index. +This changes the keys in lockstep and allows for output scripts to be indexed in the same way that the derived keys are indexed. + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>multi()</tt>, and <tt>sortedmulti()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As these are a wholly new descriptors, they are not compatible with any implementation. +However the scripts produced are standard scripts so existing software are likely to be familiar with them. + +==Reference Implemntation== + +<tt>multi()</tt>, and <tt>multi()</tt> descriptors have been implemented in Bitcoin Core since version 0.17. diff --git a/bip-0384.mediawiki b/bip-0384.mediawiki new file mode 100644 index 0000000..da7cb23 --- /dev/null +++ b/bip-0384.mediawiki @@ -0,0 +1,48 @@ +<pre> + BIP: 384 + Layer: Applications + Title: combo() Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0384 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>combo()</tt> output script descriptors. +These take a key and produce P2PK, P2PKH, P2WPKH, and P2SH-P2WPKH output scripts if applicable to the key. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +In order to make the transition from traditional key based wallets to descriptor based wallets easier, it is useful to be able to take a key and produce the scripts which have traditionally been produced by wallet software. + +==Specification== + +A new top level script expression is defined: <tt>combo(KEY)</tt>. +This expression can only be used as a top level expression. +It takes a single key expression as an argument and produces either 2 or 4 output scripts, depending on the key. +A <tt>combo()</tt> expression always produces a P2PK and P2PKH script, the same as putting the key in both a <tt>pk()</tt> and a <tt>pkh()</tt> expression. +If the key is/has a compressed public key, then P2WPKH and P2SH-P2WPKH scripts are also produced, the same as putting the key in both a <tt>wpkh()</tt> and <tt>sh(wpkh())</tt> expression. + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>combo()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As this is a wholly new descriptor, it is not compatible with any implementation. +However the scripts produced are standard scripts so existing software are likely to be familiar with them. + +==Reference Implemntation== + +<tt>combo</tt> descriptors have been implemented in Bitcoin Core since version 0.17. diff --git a/bip-0385.mediawiki b/bip-0385.mediawiki new file mode 100644 index 0000000..2469eb0 --- /dev/null +++ b/bip-0385.mediawiki @@ -0,0 +1,57 @@ +<pre> + BIP: 385 + Layer: Applications + Title: raw() and addr() Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0385 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>raw()</tt> and <tt>addr()</tt> output script descriptors. +<tt>raw()</tt> encapsulates a raw script as a descriptor. +<tt>addr()</tt> encapsulates an address as a descriptor. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +In order to make descriptors maximally compatible with scripts in use today, it is useful to be able to wrap any arbitrary output script or an address into a descriptor. + +==Specification== + +Two new script expressions are defined: <tt>raw()</tt> and <tt>addr()</tt>. + +===<tt>raw()</tt>=== + +The <tt>raw(HEX)</tt> expression can only be used as a top level descriptor. +As the argument, it takes a hex string representing a Bitcoin script. +The output script produced by this descriptor is the script represented by <tt>HEX</tt>. + +===<tt>addr()</tt>=== + +The <tt>addr(ADDR)</tt> expression can only be used as a top level descriptor. +It takes an address as its single argument. +The output script produced by this descriptor is the output script produced by the address <tt>ADDR</tt>. + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>raw()</tt> and <tt>addr()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As this is a wholly new descriptor, it is not compatible with any implementation. +The reuse of existing Bitcoin addresses allows for this to be more easily implemented. + +==Reference Implemntation== + +<tt>raw()</tt> and <tt>addr</tt> descriptors have been implemented in Bitcoin Core since version 0.17. diff --git a/bip-0386.mediawiki b/bip-0386.mediawiki new file mode 100644 index 0000000..d90e801 --- /dev/null +++ b/bip-0386.mediawiki @@ -0,0 +1,101 @@ +<pre> + BIP: 386 + Layer: Applications + Title: tr() Output Script Descriptors + Author: Pieter Wuille <pieter@wuille.net> + Andrew Chow <andrew@achow101.com> + Comments-Summary: No comments yet. + Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0386 + Status: Draft + Type: Informational + Created: 2021-06-27 + License: BSD-2-Clause +</pre> + +==Abstract== + +This document specifies <tt>tr()</tt> output script descriptors. +<tt>tr()</tt> descriptors take a key and optionally a tree of scripts and produces a P2TR output script. + +==Copyright== + +This BIP is licensed under the BSD 2-clause license. + +==Motivation== + +Taproot added one additional standard output script format: P2TR. +These expressions allow specifying those formats as a descriptor. + +==Specification== + +A new script expression is defined: <tt>tr()</tt>. +A new expression is defined: Tree Expressions + +===Tree Expression=== + +A Tree Expression (denoted <tt>TREE</tt>) is an expression which represents a tree of scripts. +The way the tree is represented in an output script is dependent on the higher level expressions. + +A Tree Expression is: +* Any Script Expression that is allowed at the level this Tree Expression is in. +* A pair of Tree Expressions consisting of: +** An open brace <tt>{</tt> +** A Tree Expression +** A comma <tt>,</tt> +** A Tree Expression +** A closing brace <tt>}</tt> + +===<tt>tr()</tt>=== + +The <tt>tr(KEY)</tt> or <tt>tr(KEY, TREE)</tt> expression can only be used as a top level expression. +All key expressions under any <tt>tr()</tt> expression must create x-only public keys. + +<tt>tr(KEY)</tt> takes a single key expression as an argument and produces a P2TR output script which does not have a script path. +Each key produced by the key expression is used as the internal key of a P2TR output as specified by [[bip-0341.mediawiki#cite_ref-22-0|BIP 341]]. +Specifically, "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''." + +<pre> +internal_key: lift_x(KEY) +32_byte_output_key: internal_key + int(HashTapTweak(bytes(internal_key)))G +scriptPubKey: OP_1 <32_byte_output_key> +</pre> + +<tt>tr(KEY, TREE)</tt> takes a key expression as the first argument, and a tree expression as the second argument and produces a P2TR output script which has a script path. +The keys produced by the first key expression are used as the internal key as specified by [[bip-0341.mediawiki#Constructing_and_spending_Taproot_outputs|BIP 341]]. +The Tree expression becomes the Taproot script tree as described in BIP 341. +A merkle root is computed from this tree and combined with the internal key to create the Taproot output key. + +<pre> +internal_key: lift_x(KEY) +merkle_root: HashTapBranch(TREE) +32_byte_output_key: internal_key + int(HashTapTweak(bytes(internal_key) || merkle_root))G +scriptPubKey: OP_1 <32_byte_output_key> +</pre> + +===Modified Key Expression=== + +Key Expressions within a <tt>tr()</tt> expression must only create x-only public keys. +Uncompressed public keys are not allowed, but compressed public keys would be implicitly converted to x-only public keys. +The keys derived from extended keys must be serialized as x-only public keys. +An additional key expression is defined only for use within a <tt>tr()</tt> descriptor: + +* A 64 hex character string representing an x-only public key + +==Test Vectors== + +TBD + +==Backwards Compatibility== + +<tt>tr()</tt> descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]]. +As these are a set of wholly new descriptors, they are not compatible with any implementation. +However the scripts produced are standard scripts so existing software are likely to be familiar with them. + +Tree Expressions are largely incompatible with existing script expressions due to the restrictions in those expressions. +As of 2021-06-27, the only allowed script expression that can be used in a tree expression is <tt>pk()</tt>. +However there will be future BIPs that specify script expressions that can be used in tree expressions. + +==Reference Implementation== + +<tt>tr()</tt> descriptors have been implemented in Bitcoin Core since version 22.0. |