Specify BIP 381: Non-segwit descriptors

Author: achow101

README.mediawiki

@@ -1057,6 +1057,13 @@ Those proposing changes should consider that ultimately consent may rest with th
 | Pieter Wuille, Andrew Chow
 | Informational
 | Draft
+|-
+| [[bip-0381.mediawiki|381]]
+| Applications
+| Non-Segwit 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! -->

bip-0380.mediawiki

@@ -238,4 +238,12 @@ 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]]
 |}

bip-0381.mediawiki

@@ -0,0 +1,83 @@
+<pre>
+  BIP: 381
+  Layer: Applications
+  Title: Non-Segwit Output Script Descriptors
+  Author: Pieter Wuille <[email protected]>
+          Andrew Chow <[email protected]>
+  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 a <tt>sh()</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.