"Russell O'Connor" <rocon...@blockstream.io> writes: > However, if I understand correctly, the situation for BIP 117 is entirely > different. As far as I understand there is currently no restrictions about > terminating a v0 witness program with a non-empty alt-stack, and there are > no restrictions on leaving non-canonical boolean values on the main stack.
BIP-141: "The script must not fail, and result in exactly a single TRUE on the stack." And it has long been non-standard for P2SH scripts to not do the same (don't know exactly when). > There could already be commitments to V0 witness programs that, when > executed in some reasonable context, leave a non-empty alt-stack and/or > leave a non-canonical true value on the main stack. Unlike the P2SH or > Segwit soft-forks, these existing commitments could be real outputs that > currently confer non-trivial ownership over their associated funds. If BIP > 117 were activated, these commitments would be subject to a new set of > rules that didn't exist when the commitments were made. In particular, > these funds could be rendered unspendable. Because segwit commitments are > hashes of segwit programs, there is no way to even analyze the blockchain > to determine if these commitments currently exist (and even if we could it > probably woudln't be adequate protection). The rule AFAICT is "standard transactions must still work". This was violated with low-S, but the transformation was arguably trivial. OTOH, use of altstack is completely standard, though in practice it's unused and so only a theoretical concern. My concern remains unanswered: I want hard numbers on the worst-case time taken by sigops with the limit removed. It's about 120 usec per sigop (from [1]), so how bad could it be? I think Russell had an estimate like 1 in 3 ops, so 160 seconds to validate a block? Thanks, Rusty. [1] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-December/015346.html _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
