From: Garlo Nicon <garlonicon@gmail•com>
To: Bitcoin Development Mailing List <bitcoindev@googlegroups.com>
Subject: [bitcoindev] Re: BIP for OP_INTERNALKEY
Date: Fri, 26 Apr 2024 01:09:24 -0700 (PDT) [thread overview]
Message-ID: <f95ca346-fc95-4cc7-9ded-1393e8dc827en@googlegroups.com> (raw)
In-Reply-To: <Zinohf1n8-aWN6G9@console>
[-- Attachment #1.1: Type: text/plain, Size: 4224 bytes --]
I wonder, what is the reason to pick 0xcb as OP_INTERNALKEY, when we had
pseudo-words OP_PUBKEY (assigned to 0xfe) and OP_PUBKEYHASH (assigned to
0xfd). Of course, those opcodes are invalid in the non-Taproot scripts, but
they were intended to be used in cases like "OP_PUBKEY OP_CHECKSIG", and
"OP_DUP OP_HASH160 OP_PUBKEYHASH OP_EQUALVERIFY OP_CHECKSIG". So, I guess
we could reuse those opcodes, and make it a general rule, that OP_PUBKEY
picks the next key from the stack (which in this specific case will give us
the internal key, but I can imagine leaving some room for extending it in
the future, with scripts like "OP_PUBKEY OP_CHECKSIGVERIFY OP_PUBKEY
OP_CHECKSIG", where each of those OP_PUBKEYs will give us a different key,
and act somewhat like OP_FROMALTSTACK, but working on a separate stack of
public keys instead, where the first key of that stack would be the
internal Taproot key).
czwartek, 25 kwietnia 2024 o 12:41:04 UTC+2 Brandon Black napisał(a):
> Hello list,
>
> I'm currently failing to find the original reference discussion for
> adding OP_INTERNALKEY to tapscript. I believe it was in the context of
> the SIGHASH_ANYPREVOUT proposal which opted instead to access the
> internalkey as a special key with value `0x01`. Regardless, here[0] is a
> BIP for adding OP_INTERNALKEY to tapscript to allow access to the
> taproot internal key. As noted below, this helps certain classes of
> script come closer to matching segwitv0 in byte efficiency, which can be
> particularly useful for protocols such as Lightning where the same
> signers may need to sign a script path in some cases, and a key path in
> others.
>
> ------------
> ## Abstract
>
> This BIP describes a new tapscript opcode (`OP_INTERNALKEY`) which
> pushes the taproot internal key to the stack.
>
> ## Specification
>
> When verifying taproot script spends having leaf version `0xc0` (as
> defined in [BIP 342]), `OP_INTERNALKEY` replaces `OP_SUCCESS203` (0xcb).
> `OP_INTERNALKEY` pushes the taproot internal key, as defined in [BIP
> 341], to the stack.
>
> ## Motivation
>
> ### Key spend with additional conditions
>
> When building taproot outputs, especially those secured by an aggregate
> key representing more than one signer, the parties may wish to
> collaborate on signing with the taproot internal key, but only with
> additional script restrictions. In this case, `OP_INTERNALKEY` saves 8
> vBytes.
>
> ### Mitigated control block overhead for scripts using hash locks
>
> In cases where script path spending is not desired, the internal key may
> be set to a NUMS point whose bytes would otherwise be required in a
> tapscript. This could be used with any hash locked transaction, for
> example, to save 8 vBytes.
>
> Note: The internal key must be the X coordinate of a point on the
> SECP256K1 curve, so any such hash must be checked and modified until it
> is such an X coordinate. This will typically take approximately 2
> attempts.
>
> ## Reference Implementation
>
> A reference implementation is provided here:
>
> https://github.com/bitcoin/bitcoin/pull/29269
>
> ## Backward Compatibility
>
> By constraining the behavior of an OP_SUCCESS opcode, deployment of the
> BIP can be done in a backwards compatible, soft-fork manner. If anyone
> were to rely on the OP_SUCCESS behavior of `OP_SUCCESS203`,
> `OP_INTERNALKEY` would invalidate their spend.
>
> ## Deployment
>
> TBD
>
> ## Copyright
>
> This document is licensed under the 3-clause BSD license.
>
> [BIP 341]: https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki
>
> [BIP 342]: https://github.com/bitcoin/bips/blob/master/bip-0342.mediawiki
>
> ------------
>
> [0]: https://github.com/bitcoin/bips/pull/1534
>
> --
> --Brandon
>
--
You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com.
To view this discussion on the web visit https://groups.google.com/d/msgid/bitcoindev/f95ca346-fc95-4cc7-9ded-1393e8dc827en%40googlegroups.com.
[-- Attachment #1.2: Type: text/html, Size: 6033 bytes --]
next prev parent reply other threads:[~2024-04-26 9:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 5:22 [bitcoindev] " Brandon Black
2024-04-26 8:09 ` Garlo Nicon [this message]
2024-04-26 16:03 ` [bitcoindev] " Brandon Black
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f95ca346-fc95-4cc7-9ded-1393e8dc827en@googlegroups.com \
--to=garlonicon@gmail$(echo .)com \
--cc=bitcoindev@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox