If a block that would be discarded under previous rules becomes accepted after a rule addition, there is no reason to not simply call the new rule a hard fork. IOW it's perfectly rational to consider a weaker block as "invalid" relative to the strong chain. As such I don't see any reason to qualify the term, it's a hard fork. But Peter's observation (the specific behavior) is ultimately what matters. e > On Nov 6, 2017, at 12:30, Paul Sztorc via bitcoin-dev wrote: > > +1 to all of Peter Todd's comments > >> On Nov 6, 2017 11:50 AM, "Peter Todd via bitcoin-dev" wrote: >> On Wed, Nov 01, 2017 at 05:48:27AM +0000, Devrandom via bitcoin-dev wrote: >> >> Some quick thoughts... >> >> > Hi all, >> > >> > Feedback is welcome on the draft below. In particular, I want to see if >> > there is interest in further development of the idea and also interested in >> > any attack vectors or undesirable dynamics. >> > >> > (Formatted version available here: >> > https://github.com/devrandom/btc-papers/blob/master/aux-pow.md ) >> > >> > # Soft-fork Introduction of a New POW >> >> First of all, I don't think you can really call this a soft-fork; I'd call it a >> "pseudo-soft-fork" >> >> My reasoning being that after implementation, a chain with less total work than >> the main chain - but more total SHA256^2 work than the main chain - might be >> followed by non-supporting clients. It's got some properties of a soft-fork, >> but it's security model is definitely different. >> >> > ### Aux POW intermediate block >> > >> > Auxiliary POW blocks are introduced between normal blocks - i.e. the chain >> > alternates between the two POWs. >> > Each aux-POW block points to the previous normal block and contains >> > transactions just like a normal block. >> > Each normal block points to the previous aux-POW block and must contain all >> > transactions from the aux-POW block. >> >> Note how you're basically proposing for the block interval to be decreased, >> which has security implications due to increased orphan rates. >> >> > ### Heaviest chain rule change >> > >> > This is a semi-hard change, because non-upgraded nodes can get on the wrong >> > chain in case of attack. However, >> >> Exactly! Not really a soft-fork. >> >> -- >> https://petertodd.org 'peter'[:-1]@petertodd.org >> >> _______________________________________________ >> 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