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From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
To: Zac Greenwood <zachgrw@gmail.com>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] User Resisted Soft Fork for CTV
Date: Mon, 25 Apr 2022 10:01:28 +0000	[thread overview]
Message-ID: <ID4VQ7kbkdRwf38kiXtxuhanlkFy7ggmL26NlK_t4h9KdAzrIMFXGdgwsGxIixQXhkdyeaSupmVEVDp14aQPwShHm1AryWFiYAkZO5Thb4k=@protonmail.com> (raw)
In-Reply-To: <CAJ4-pEB1zWxWapt3qit=X1p3WuSSn2_K=rygDp8JzpS7GimgMg@mail.gmail.com>

Good morning Zac,

> On Mon, 25 Apr 2022 at 07:36, ZmnSCPxj <zmnscpxj@protonmail.com> wrote
>
> > CTV *can* benefit layer 2 users, which is why I switched from vaguely apathetic to CTV, to vaguely supportive of it.
>
>
> Other proposals exist that also benefit L2 solutions. What makes you support CTV specifically?

It is simple to implement, and a pure `OP_CTV` SCRIPT on a P2WSH / P2SH is only 32 bytes + change on the output and 32 bytes + change on the input/witness, compared to signature-based schemes which require at least 32 bytes + change on the output and 64 bytes + change on the witness ***IF*** they use the Taproot format (and since we currently gate the Taproot format behind actual Taproot usages, any special SCRIPT that uses Taproot-format signatures would need at least the 33-byte internal pubkey revelation; if we settle with the old signature format, then that is 73 bytes for the signature).
To my knowledge as well, hashes (like `OP_CTV` uses) are CPU-cheaper (and memory-cheaper?) than even highly-optimized `libsecp256k1` signature validation, and (to my knowledge) you cannot use batch validation for SCRIPT-based signature checks.
It definitely does not enable recursive covenants, which I think deserve more general research and thinking before we enable recursive covenants.

Conceptually, I see `OP_CTV` as the "AND" to the "OR" of MAST.
In both cases, you have a hash-based tree, but in `OP_CTV` you want *all* these pre-agreed cases, while in MAST you want *one* of these pre-agreed cases.

Which is not to say that other proposals do not benefit L2 solutions *more* (`SIGHASH_ANYPREVOUT` when please?), but other proposals are signature-based and would be larger in this niche.

Regards,
ZmnSCPxj


  reply	other threads:[~2022-04-25 10:01 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-21 16:45 [bitcoin-dev] User Resisted Soft Fork for CTV Michael Folkson
2022-04-21 23:36 ` Keagan McClelland
2022-04-22  9:03   ` Zac Greenwood
2022-04-22 15:40     ` Corey Haddad
2022-04-23  5:07       ` Billy Tetrud
2022-04-23 14:48         ` Erik Aronesty
2022-04-24 14:47     ` Peter Todd
2022-04-25  5:36       ` ZmnSCPxj
2022-04-25  9:06         ` Zac Greenwood
2022-04-25 10:01           ` ZmnSCPxj [this message]
2022-04-22  9:53   ` Michael Folkson
2022-04-23 20:40 ` Jorge Timón
2022-04-24 12:17   ` Michael Folkson
2022-04-24 12:57     ` Jorge Timón
2022-04-24 12:55   ` Ryan Grant
2022-04-24 13:11     ` Jorge Timón
2022-04-24 13:15       ` Ryan Grant
2022-04-25 16:11 alicexbt

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