From: Luke Dashjr <luke@dashjr.org>
To: bitcoin-dev@lists.linuxfoundation.org,
	Jorge =?iso-8859-1?q?Tim=F3n?= <jtimon@jtimon.cc>
Date: Wed, 31 May 2017 04:14:25 +0000
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Subject: Re: [bitcoin-dev] Hypothetical 2 MB hardfork to follow BIP148
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On Wednesday 31 May 2017 1:22:44 AM Jorge Tim=F3n via bitcoin-dev wrote:
> Why is it
> https://github.com/bitcoin/bitcoin/blob/master/src/validation.cpp#L1661
> not enough at this point?
> Why the need for a transaction size limit?

Because the bottleneck is hashing the transaction, which costs (in CPU time=
)=20
based on its size. Maybe it would make sense to factor sigops into the limi=
t,=20
though?

On Wednesday 31 May 2017 1:09:26 AM Jean-Paul Kogelman via bitcoin-dev wrot=
e:
> On May 30, 2017, at 4:50 PM, James MacWhyte wrote:
> > Add a transaction-size limit of, say, 10kb and the quadratic hashing
> > problem is a non-issue. Donezo.
>
> That would invalidate any pre-signed transactions that are currently out
> there. You can't just change the rules out from under people.

Make it 100kB and I think we'd be okay. Those have always been policy-
forbidden so there should be no expectation they'd be acceptable in the=20
future.

While we're at it, I suggest also specifying a minimum transaction size as=
=20
well. The raw minimum possible is 60 bytes, but any sane output would need =
at=20
least a hash, so I'd say make the minimum be 8 (60 + 160-bit hash) bytes?

Luke