From: Luke Dashjr <luke@dashjr•org>
To: bitcoin-dev@lists•linuxfoundation.org, Johnson Lau <jl2012@xbt•hk>
Subject: Re: [bitcoin-dev] New BIP: Dealing with OP_IF and OP_NOTIF malleability in P2WSH
Date: Wed, 17 Aug 2016 04:40:34 +0000 [thread overview]
Message-ID: <201608170440.35767.luke@dashjr.org> (raw)
In-Reply-To: <976728541.94211.1471402973613@privateemail.com>
On Wednesday, August 17, 2016 3:02:53 AM Johnson Lau via bitcoin-dev wrote:
> To completely replicate the original behaviour, one may use:
> "DEPTH TOALTSTACK IFDUP DEPTH FROMALTSTACK NUMNOTEQUAL IF 2DROP {if script}
> ELSE DROP {else script} ENDIF"
This is much uglier than expected. IMO if that's the best workaround for the
current behaviour, people should just use "OP_1 OP_EQUAL OP_IF" when/if they
need to avoid malleability issues.
I suspect most cases OP_IF would be used, you really want to accept any non-
zero value. For example, the HTLC script I posted on the list about not long
ago (OP_IF operates on the result from OP_SIZE). Counter-examples would be BIP
124, the examples in BIP 65 and BIP 112, but I note all of these could be just
as easily done without the explicit boolean being fed to the OP_IF (you'd need
an OP_DUP to keep the value, so it wouldn't reduce the byte-size).
Of course, as long as we're talking about a softfork activating together with
segwit, and only having effect in segwit scripts... there's no reason we can't
add whatever opcodes we need so long as it gets done before 0.13.1. I suggest
OP_CASTTOBOOL and OP_DUPASBOOL would be two good candidates if we make OP_IF
stricter. There's also the possibility of adding an OP_RETAINIF which behaves
as the current OP_IF, except not popping the conditional value off the stack.
But perhaps this is getting too complicated for testing in time for segwit...
Luke
next prev parent reply other threads:[~2016-08-17 4:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-16 17:53 Johnson Lau
2016-08-16 19:37 ` Luke Dashjr
2016-08-16 19:43 ` Peter Todd
2016-08-16 21:58 ` Joseph Poon
2016-08-16 22:23 ` Russell O'Connor
2016-08-16 22:30 ` Pieter Wuille
2016-08-16 22:36 ` Russell O'Connor
2016-08-16 22:39 ` Pieter Wuille
2016-08-16 22:52 ` Russell O'Connor
2016-08-17 0:18 ` Gregory Maxwell
2016-08-17 0:27 ` Russell O'Connor
2016-08-17 2:30 ` Peter Todd
2016-08-17 3:02 ` Johnson Lau
2016-08-17 4:40 ` Luke Dashjr [this message]
2016-08-17 10:15 ` Johnson Lau
2016-08-18 0:11 ` Sergio Demian Lerner
[not found] ` <CAAS2fgQ=Z+xmg0DcANV4vhp+XhpL1Vz0HNkJwNGdHTxtK1q1kg@mail.gmail.com>
2016-08-18 0:33 ` Sergio Demian Lerner
2016-08-18 3:00 ` Peter Todd
2016-09-05 14:55 ` Russell O'Connor
2016-09-01 11:39 ` Johnson Lau
2016-09-05 1:32 ` Rusty Russell
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