Clarify exactly which scripts are witness outputs #1537

sipa commented at 6:10 PM on January 8, 2024: member

No description provided.

josibake commented at 6:33 PM on January 8, 2024: member

ACK https://github.com/bitcoin/bips/pull/1537/commits/ff9feab538e7f814a694ad92f4487f998649b920

LGTM, clears up the confusion I had regarding OP_PUSHBYTES_x vs OP_PUSHDATA1 x.

in bip-0141.mediawiki:89 in ff9feab538 outdated

  82 | @@ -83,19 +83,23 @@ If all transactions in a block do not have witness data, the commitment is optio
  83 |  
  84 |  === Witness program ===
  85 |  
  86 | -A <code>scriptPubKey</code> (or <code>redeemScript</code> as defined in BIP16/P2SH) that consists of a 1-byte push opcode (for 0 to 16) followed by a data push between 2 and 40 bytes gets a new special meaning. The value of the first push is called the "version byte". The following byte vector pushed is called the "witness program".
  87 | +A <code>scriptPubKey</code> (or <code>redeemScript</code> as defined in BIP16/P2SH) that consists of a 1-byte push opcode (<code>OP_0</code> through <code>OP_16</code>) followed by a direct data push between 2 and 40 bytes gets a new special meaning. The value of the first push is called the "version byte". The following byte vector pushed is called the "witness program".
  88 | +In more detail, this means a <code>scriptPubKey</code> or <code>redeemScript</code> which consists of (in order):
  89 | +* First, byte 0x00 (<code>OP_0</code>) or any byte between 0x51 (<code>OP_1</code>) and 0x60 (<code>OP_16</code>) inclusive (the version byte).
  90 | +* Then, a byte ''L'' between 0x02 (push of 2 bytes) and 0x18 (push of 40 bytes) inclusive.

ajtowns commented at 5:28 AM on January 14, 2024:

0x18 should be 0x28 presumably

sipa commented at 12:27 PM on April 26, 2024:

Fixed.

Clarify exactly which scripts are witness outputs 50e750a882

sipa force-pushed on Apr 26, 2024

sipa commented at 12:29 PM on April 26, 2024: member

Rebased after the merge of #487. I believe the text here contains further improvements.

in bip-0141.mediawiki:86 in 50e750a882

  82 | @@ -83,19 +83,23 @@ If all transactions in a block do not have witness data, the commitment is optio
  83 |  
  84 |  === Witness program ===
  85 |  
  86 | -A <code>scriptPubKey</code> (or <code>redeemScript</code> as defined in BIP16/P2SH) that consists of a select subset of opcodes (<code>OP_0,OP_1,OP_2,...,OP_16</code>) followed by a data push between 2 and 40 bytes gets a new special meaning. The value of the first push is called the "version byte". The following byte vector pushed is called the "witness program".
  87 | +A <code>scriptPubKey</code> (or <code>redeemScript</code> as defined in BIP16/P2SH) that consists of a 1-byte push opcode (one of <code>OP_0,OP_1,OP_2,...,OP_16</code>) followed by a direct data push between 2 and 40 bytes gets a new special meaning. The value of the first push is called the "version byte". The following byte vector pushed is called the "witness program".

vostrnad commented at 12:35 PM on April 26, 2024:

I'm not sure about the added word "direct" here. Perhaps "canonical" or "minimal" would be clearer?

sipa commented at 12:54 PM on April 26, 2024:

These are the terms as I use them. Bitcoin script knows 3 types of pushes:

The OP_n opcodes (0x4f through 0x60, inclusive)
The direct pushes (0x01 through 0x4b)
The OP_PUSHDATA opcodes (0x4c through 0x4e)

By "minimal push" I understand "whichever of those 3 types that is applicable and minimal in encoded size". It happens to be the case that in this context (for pushes of 2 to 40 bytes) the direct push is always the minimal one, but that seems like a very indirect way of describing it.

It's true that there isn't any well-established terminology for what I call direct pushes here, but given that it's clarified explicitly immediately after, is that an issue?

vostrnad commented at 1:44 PM on April 26, 2024:

Thank you for the clarification, the word "direct" makes complete sense now.

jonathancross commented at 7:13 PM on April 26, 2024: contributor

ACK https://github.com/bitcoin/bips/pull/1537/commits/50e750a882f525cc9a297b75ca35682f3deb1f95

murchandamus approved

murchandamus commented at 9:25 PM on April 26, 2024: contributor

ACK 50e750a882f525cc9a297b75ca35682f3deb1f95

murchandamus merged this on Apr 26, 2024

murchandamus closed this on Apr 26, 2024