Subject: Re: [Bitcoin-development] 0.8.1 ideas

From: Peter Todd <[email-masked]>
Date: Wed, 13 Mar 2013 11:05:01 -0400

On Wed, Mar 13, 2013 at 12:56:29PM +0000, Luke-Jr wrote:
> Here's a simple proposal to start discussion from...
> 
> BEFORE block 262144:
> - Never make a block that, combined with the previous 4 blocks, results in 
> over 4500 transaction modifications.
> - Reject any block that includes more than 4500 transaction modifications on 
> its own (slight soft-fork)
> - (these rules should make older clients safe under most circumstances)
> 
> FROM block 262144 to block 393216 (hard fork #1):
> - Never make, and reject any block that includes more than 24391 transaction 
> modifications on its own (this *should* be equivalent to 1 MB)
> - (this rules can make older client backports safe unless a reorg is more than 
> 6 blocks deep)
> 
> FROM block 393216 onward (hard fork #2):
> - Never make, and reject any block that includes more than 48781 transaction 
> modifications on its own (this *should* be equivalent to 2 MB)
> - Accept blocks up to 2 MB in data size

If we're going to consider doing this, at minimum we need to also
include a separate limit for how much the UTXO set can be grown by each
block, calculated as the size of the scriptPubKey + constant metadata.
(tx hash, index #, nValue, nVersion, nHeight should cover it)

A P2SH transaction txout would measure 71bytes under that model. Given
that we haven't even shown we can limit the creation of txouts that can
not be spent economically caution would dictate setting the UTXO growth
limit fairly low, say 1/4th of the block limit.

-- 
'peter'[:-1]@petertodd.org