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Date: Mon, 20 Jul 2015 20:55:57 +0000
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From: Gregory Maxwell <gmaxwell@gmail.com>
To: Gavin Andresen <gavinandresen@gmail.com>
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Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] For discussion: limit transaction size to
	mitigate CVE-2013-2292
Precedence: list

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.

The cost of the indirection is forclosing future applications which
involve larger signatures but have no quadratic component and are thus
fast to verify-- or requring yet another hard fork to remove the
limit, or a kludgy soft fork that splits the same data across two
"transactions" which get processed as a unit... all would be
unfortunate.

Alternative 1 sounds more attractive to be for this reason as it's more direct.