From: "Russell O'Connor" <roconnor@blockstream•io>
To: Johnson Lau <jl2012@xbt•hk>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Safer sighashes and more granular SIGHASH_NOINPUT
Date: Thu, 22 Nov 2018 17:10:11 -0500 [thread overview]
Message-ID: <CAMZUoKkdjHYd8BR6PCae-UG_QRoujW36kYf8s4Gk2FVBeSJnrw@mail.gmail.com> (raw)
In-Reply-To: <8CD6C248-9ADF-4324-B4E3-DE41A1ED49A9@xbt.hk>
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On Thu, Nov 22, 2018 at 3:53 PM Johnson Lau <jl2012@xbt•hk> wrote:
> Assuming a script size of 128 bytes (including SHA256 padding), 2^20
> scripts is 134MB. Double it to 268MB for the merkle branch hashes. With
> roughly 100MB/s, this should take 2.5s (or 42min for 30 levels). However,
> memory use is not considered.
>
> >each call to this operation effectively takes O(script-size) time
> I’m not sure if this is correct. Actually,
> CTransactionSignatureSerializer() scans every script for OP_CODESEPARATOR.
> Scripts with and without OP_CODESEPARATOR should take exactly the same
> O(script-size) time (see https://github.com/bitcoin/bitcoin/pull/14786)
> Also, this is no longer a concern under segwit (BIP143), which
> CTransactionSignatureSerializer() is not used. Actually, OP_CODESEPARATOR
> under segwit is way simpler than the proposed OP_MASK. If one finds OP_MASK
> acceptable, there should be no reason to reject OP_CODESEPARATOR.
>
Even still, each call to OP_CODESEPARATOR / OP_CHECKSIG pair requires
recomputing a new #5. scriptCode from BIP 143, and hence computes a new
transaction digest. I understood that this issue was the main motivation
for wanting to deprecate OP_CODESEPARATOR and remove it from later versions
of script.
However, given that we are looking at a combinatorial explosion in SIGHASH
flag combinations already, coupled with existing SigOp limitations, maybe
the cost of recomputing scriptCode with OP_CODESEPARATOR isn't such a big
deal.
And even if we choose remove the behavior of OP_CODESEPARATOR in new
versions of Script, it seems more than 30 layers of sequential OP_IFs can
be MASTified, so there is no need to use OP_CODESEPARATOR within that limit.
>One suggestion I heard (I think I heard it from Pieter) to achieve the
above is to add an internal counter that increments on every control flow
operator,……...
> If I have to choose among OP_CODESEPARATOR and “flow operator counting”,
> I’d rather choose OP_CODESEPARATOR. At least we don’t need to add more
> lines to the consensus code, just for something that is mostly archivable
> with MAST.
>
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next prev parent reply other threads:[~2018-11-22 22:10 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-19 22:37 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 [this message]
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
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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