Gregory Maxwell <gmaxw...@gmail.com> writes: > I'm not a great fan of this proposal for two reasons: The first is > that the strict ordering requirements is incompatible with future > soft-forks that may expose additional ordering constraints. Today we > have _SINGLE, which as noted this interacts with poorly, but there > have been other constraints proposed that this would also interact > with poorly.
Yes, I hit this when I implemented an IsStandard change; upon input evaluation the scriptsigs which used _SINGLE get disregarded from ordering. > The second is that even absent consensus rules there may be invisible > constraints in systems-- e.g. hardware wallets that sign top down, I think that one's pretty easy to fix (and they should fix it anyway, to avoid leaking information due to ordering): they can receive an unordered tx and sign it as if it were ordered canonically. > or > future transaction covenants that have constraints about ordering, or > proof systems that use (yuck) midstate compression for efficiency. The softfork argument I find the most compelling, though it's tempting to argue that every ordering use (including SIGHASH_SINGLE) is likely a mistake. > I think perhaps the motivations here are understated. We have not seen > any massive deployments of accidentally broken ordering that I'm aware > of-- and an implementation that got this wrong in a harmful way would > likely make far more fatal mistakes (e.g. non random private keys). I was prompted to propose something by this: https://blog.blocktrail.com/2015/05/getting-your-change-in-order/ If that's the only one though, it's less compelling. > As an alternative to this proposal the ordering can be privately > derandomized in the same way DSA is, to avoid the need for an actual > number source. If getting the randomness right were really the only > motivation, I'd suggest we propose a simple derandomized randomization > algorithm--- e.g. take the order from (H(input ids||client secret)). > > I think there is actually an unstated motivation also driving this > (and the other) proposal related to collaborative transaction systems > like coinjoins or micropayment channels; where multiple clients need > to agree on the same ordering. Is this the case? If so we should > probably talk through some of the requirements there and see if there > isn't a better way to address it. Indeed. I was implementing deterministic permutations for lightning (signature exchange requires both sides agree on ordering). Cheers, Rusty. ------------------------------------------------------------------------------ _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
