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From: Anthony Towns <aj@erisian.com.au>
To: Russell O'Connor <roconnor@blockstream.io>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Safer sighashes and more granular SIGHASH_NOINPUT
Date: Thu, 13 Dec 2018 10:05:53 +1000	[thread overview]
Message-ID: <20181213000553.cikilodf65an225g@erisian.com.au> (raw)
In-Reply-To: <CAMZUoKkYcXt7O39zdpz494f9Jm195mBtWyrH3siX4PBEAf8OKQ@mail.gmail.com>

On Tue, Dec 11, 2018 at 05:50:24PM -0500, Russell O'Connor via bitcoin-dev wrote:
> On Sun, Dec 9, 2018 at 2:13 PM Johnson Lau <jl2012@xbt.hk> wrote:
>     The current proposal is that a 64-byte signature will be used for the
>     default “signing all” sighash, and 65-byte for other sighash types. The
>     space saved will allow a few more txs in a block, so I think it worths
>     doing. However, this also makes witness weight estimation more difficult in
>     multisig cases.

This seems strange to me -- why wouldn't you just assume every signature
is 65 witness bytes, and just be grateful for the prioritisation benefit
if someone chooses a shorter signature? Your error margin is just 0.25
vbytes per signature.

> I tend to think in opposite terms. Is there a proof that any script can be
> transformed into an equivalent one that avoids witness weight malleability?

An alternative generalisation: is there a proof that all valid witnesses
will have a weight within some small range?

> Moreover, even if witness weight malleability is entirely avoidable, it always
> seems to come at a cost.  Taking as an example libwally's proposed "
> csv_2of3_then_2" Script, it begins with "OP_DEPTH OP_1SUB OP_1SUB"

(DEPTH 2 NUMNOTEQUAL seems like it would have been more obvious...)

Cheers,
aj



  parent reply	other threads:[~2018-12-13  0:06 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-19 22:37 [bitcoin-dev] Safer sighashes and more granular SIGHASH_NOINPUT Pieter Wuille
2018-11-20 20:29 ` Anthony Towns
2018-11-21 11:20   ` Christian Decker
2018-11-21 17:55   ` Johnson Lau
2018-11-21 11:15 ` Christian Decker
2018-11-23  6:04   ` Anthony Towns
2018-11-23  9:40     ` Christian Decker
2018-11-24  8:13       ` Johnson Lau
2018-11-21 17:07 ` Russell O'Connor
2018-11-22 14:28   ` Johnson Lau
2018-11-22 16:23     ` Russell O'Connor
2018-11-22 20:52       ` Johnson Lau
2018-11-22 22:10         ` Russell O'Connor
2018-11-23 10:47           ` Johnson Lau
2018-11-23  5:03   ` Anthony Towns
2018-11-23 20:18     ` Russell O'Connor
2018-11-28  3:41 ` Pieter Wuille
2018-11-28  8:31   ` Johnson Lau
2018-11-29 17:00   ` Christian Decker
2018-11-29 18:29     ` Christian Decker
2018-12-06 16:57   ` Russell O'Connor
2018-12-09 19:13     ` Johnson Lau
2018-12-11 22:50       ` Russell O'Connor
2018-12-12 19:53         ` Johnson Lau
2018-12-13 16:50           ` Russell O'Connor
2018-12-13  0:05         ` Anthony Towns [this message]
2018-12-13 16:21           ` Russell O'Connor
2018-12-14  0:47             ` Anthony Towns
     [not found]         ` <CAAS2fgRma+Pw-rHJSOKRVBqoxqJ3AxHO9d696fWoa-sb17JEOQ@mail.gmail.com>
2018-12-13 16:34           ` Russell O'Connor
2018-12-09 22:41     ` David A. Harding
2018-12-11 15:36       ` Russell O'Connor
2018-12-11 17:47         ` David A. Harding
2018-12-12  9:42 ` Rusty Russell
2018-12-12 20:00   ` Johnson Lau
2018-12-12 23:49     ` Rusty Russell
2018-12-13  0:37       ` Rusty Russell
2018-12-14  9:30         ` Anthony Towns
2018-12-14 13:55           ` Johnson Lau
2018-12-17  3:10             ` Rusty Russell
2018-12-20 19:34               ` Johnson Lau
2018-12-20 23:17                 ` Rusty Russell
2018-12-21 18:54                   ` Johnson Lau
2018-12-23  4:26                     ` Anthony Towns
2018-12-23 16:33                       ` Johnson Lau
2018-12-24 12:01                         ` ZmnSCPxj
2018-12-24 21:23                           ` Johnson Lau
2018-12-16  6:55           ` Rusty Russell
2018-12-17 19:08             ` Johnson Lau
2018-12-18  4:22               ` Peter Todd
2018-12-19  0:39               ` Rusty Russell
2019-02-09  0:39                 ` Pieter Wuille
2018-12-13  0:24   ` Anthony Towns
2018-11-28  0:54 Bob McElrath
2018-11-28  8:40 ` Johnson Lau
2018-11-28 14:04   ` Bob McElrath

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