Yea, I think in any hardfork that we should be talking about, a part of it should include 1) fix the version field so its a static constant, 2) the merkle root becomes hash of the real block header 3) swap first 2 bytes of the merkle root with the timestamp's two high-order bits, 4) swap the next 4 bytes of the merkle root with the difficulty field.
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I believe this should be compatible with all existing ASICs, with the exception, possibly, of some 21 Inc hardware. I believe this fixes AsicBoost (without thinking about it tooo much, so please critique). While this is somewhat nasty, the risks of AsicBoost and the precedent that should be set necessitates a response, and it should be included in any hardfork. Matt On 05/10/16 20:27, Tier Nolan via bitcoin-dev wrote: > The various chunks in the double SHA256 are > > Chunk 1: 64 bytes > version > previous_block_digest > merkle_root[31:4] > > Chunk 2: 64 bytes > merkle_root[3:0] > nonce > timestamp > target > > Chunk 3: 64 bytes > digest from first sha pass > > Their improvement requires that all data in Chunk 2 is identical except > for the nonce. With 4 bytes, the birthday paradox means collisions can > be found reasonable easily. > > If hard forks are allowed, then moving more of the merkle root into the > 2nd chunk would make things harder. The timestamp and target could be > moved into chunk 1. This increases the merkle root to 12 bytes in the > 2nd chunk. Finding collisions would be made much more difficult. > > If ASIC limitations mean that the nonce must stay where it is, this > would mean that the merkle root would be split into two pieces. > > On Tue, May 10, 2016 at 7:57 PM, Peter Todd via bitcoin-dev > <bitcoin-dev@lists.linuxfoundation.org > <mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote: > > As part of the hard-fork proposed in the HK agreement(1) we'd like > to make the > patented AsicBoost optimisation useless, and hopefully make further > similar > optimizations useless as well. > > What's the best way to do this? Ideally this would be SPV > compatible, but if it > requires changes from SPV clients that's ok too. Also the fix this > should be > compatible with existing mining hardware. > > > 1) > > https://medium.com/@bitcoinroundtable/bitcoin-roundtable-consensus-266d475a61ff > > 2) > > http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-April/012596.html > > -- > https://petertodd.org 'peter'[:-1]@petertodd.org <http://petertodd.org> > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > <mailto:bitcoin-dev@lists.linuxfoundation.org> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > > > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
