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From: Gavin Andresen <gavinandresen@gmail.com>
To: Gregory Maxwell <gmaxwell@gmail.com>
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] For discussion: limit transaction size to mitigate CVE-2013-2292
Date: Tue, 21 Jul 2015 14:09:19 -0400	[thread overview]
Message-ID: <CABsx9T2ZX3iuCN4g6Yh0k8R7Ad0yx-yfx1f2XhCEPtz-vt2xsw@mail.gmail.com> (raw)
In-Reply-To: <CAAS2fgRBa47ye-ouV2jDe16MJFCKxYh0zF0Jw4BTwzpXVKgwOg@mail.gmail.com>

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On Mon, Jul 20, 2015 at 4:55 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:

> On Mon, Jul 20, 2015 at 7:10 PM, Gavin Andresen via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
> > Mitigate a potential CPU exhaustion denial-of-service attack by limiting
> > the maximum size of a transaction included in a block.
>
> This seems like a fairly indirect approach. The resource being watched
> for is not the size (otherwise two transactions for 200k would be
> strictly worse than one 200k transactions) but the potential of N^2
> costs related to repeated hashing in checksig; which this ignores.
>

Yes.  The tradeoff is implementation complexity: it is trivial to check
transaction size,
not as trivial to count signature operations, because
number-of-bytes-in-transaction
doesn't require any context.

But I would REALLY hate myself if in ten years a future version of me was
struggling to
get consensus to move away from some stupid 100,000 byte transaction size
limit
I imposed to mitigate a potential DoS attack.

So I agree, a limit on sigops is the right way to go. And if that is being
changed,
might as well accurately count exactly how many sigops a transaction
actually
requires to be validated...

-- 
--
Gavin Andresen

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  reply	other threads:[~2015-07-21 18:09 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-20 19:10 [bitcoin-dev] For discussion: limit transaction size to mitigate CVE-2013-2292 Gavin Andresen
2015-07-20 19:43 ` Tier Nolan
2015-07-20 20:30   ` Gavin Andresen
2015-07-20 19:58 ` Ross Nicoll
2015-07-20 20:55 ` Gregory Maxwell
2015-07-21 18:09   ` Gavin Andresen [this message]
2015-07-21 18:18     ` Jeremy Rubin
2015-07-23 15:41   ` Gavin Andresen
2015-07-24 20:59     ` Gavin Andresen
2015-07-25  0:47       ` odinn

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