Hi list, Thanks to the annex covered by the signature, I don't see how the concern about limiting the extensibility of bitcoin script with future (post-quantum) cryptographic schemes. Previous proposal of the annex were deliberately designed with variable-length fields to flexibly accomodate a wide range of things. I believe there is one thing that has not been proposed to limit unpredictable utterance of spams on the blockchain, namely congestion control of categories of outputs (e.g "fat" scriptpubkeys). Let's say P a block period, T a type of scriptpubkey and L a limiting threshold for the number of T occurences during the period P. Beyond the L threshold, any additional T scriptpubkey is making the block invalid. Or alternatively, any additional T generating / spending transaction must pay some weight penalty... Congestion control, which of course comes with its lot of shenanigans, is not very a novel idea as I believe it has been floated few times in the context of lightning to solve mass closure, where channels out-priced at current feerate would have their safety timelocks scale ups. No need anymore to come to social consensus on what is quantitative "spam" or not. The blockchain would automatically throttle out the block space spamming transaction. Qualitative spam it's another question, for anyone who has ever read shannon's theory of communication only effective thing can be to limit the size of data payload. But probably we're kickly back to a non-mathematically solvable linguistical question again [0]. Anyway, in the sleeping pond of consensus fixes fishes, I'm more in favor of prioritizing a timewarp fix and limiting dosy spends by old redeem scripts, rather than engaging in shooting ourselves in the foot with ill-designed "spam" consensus mitigations. [0] If you have a soul of logician, it would be an interesting demonstration to come with to establish that we cannot come up with mathematically or cryptographically consensus means to solve qualitative "spam", which in a very pure sense is a linguistical issue. Best, Antoine OTS hash: 6cb50fe36ca0ec5cb9a88517dd4ce9bb50dd6ad1d2d6a640dd4a31d72f0e4999 Le vendredi 17 octobre 2025 à 19:45:44 UTC+1, Antoine Poinsot a écrit : > Hi, > > This approach was discussed last year when evaluating the best way to > mitigate DoS blocks in terms > of gains compared to confiscatory surface. Limiting the size of created > scriptPubKeys is not a > sufficient mitigation on its own, and has a non-trivial confiscatory > surface. > > One of the goal of BIP54 is to address objections to Matt's earlier > proposal, notably the (in my > opinion reasonable) confiscation concerns voiced by Russell O'Connor. > Limiting the size of > scriptPubKeys would in this regard be moving in the opposite direction. > > Various approaches of limiting the size of spent scriptPubKeys were > discussed, in forms that would > mitigate the confiscatory surface, to adopt in addition to (what > eventually became) the BIP54 sigops > limit. However i decided against including this additional measure in > BIP54 because: > - of the inherent complexity of the discussed schemes, which would make it > hard to reason about > constructing transactions spending legacy inputs, and equally hard to > evaluate the reduction of > the confiscatory surface; > - more importantly, there is steep diminishing returns to piling on more > mitigations. The BIP54 > limit on its own prevents an externally-motivated attacker from *unevenly* > stalling the network > for dozens of minutes, and a revenue-maximizing miner from regularly > stalling its competitions > for dozens of seconds, at a minimized cost in confiscatory surface. > Additional mitigations reduce > the worst case validation time by a smaller factor at a higher cost in > terms of confiscatory > surface. It "feels right" to further reduce those numbers, but it's less > clear what the tangible > gains would be. > > Furthermore, it's always possible to get the biggest bang for our buck in > a first step and going the > extra mile in a later, more controversial, soft fork. I previously floated > the idea of a "cleanup > v2" in private discussions, and i think besides a reduction of the maximum > scriptPubKey size it > should feature a consensus-enforced maximum transaction size for the > reasons stated here: > > https://delvingbitcoin.org/t/non-confiscatory-transaction-weight-limit/1732/8. > I wouldn't hold my > breath on such a "cleanup v2", but it may be useful to have it documented > somewhere. > > I'm trying to not go into much details regarding which mitigations were > considered in designing > BIP54, because they are tightly related to the design of various DoS > blocks. But i'm always happy to > rehash the decisions made there and (re-)consider alternative approaches > on the semi-private Delving > thread [0] dedicated to this purpose. Feel free to ping me to get access > if i know you. > > Best, > Antoine Poinsot > > [0]: https://delvingbitcoin.org/t/worst-block-validation-time-inquiry/711 > > > > > On Friday, October 17th, 2025 at 1:12 PM, Brandon Black < > fre...@reardencode.com> wrote: > > > > > > > On 2025-10-16 (Thu) at 00:06:41 +0000, Greg Maxwell wrote: > > > > > But also given that there are essentially no violations and no reason > to > > > expect any I'm not sure the proposal is worth time relative to fixes of > > > actual moderately serious DOS attack issues. > > > > > > I believe this limit would also stop most (all?) of PortlandHODL's > > DoSblocks without having to make some of the other changes in GCC. I > > think it's worthwhile to compare this approach to those proposed by > > Antoine in solving these DoS vectors. > > > > Best, > > > > --Brandon > > > > -- > > You received this message because you are subscribed to the Google > Groups "Bitcoin Development Mailing List" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to bitcoindev+...@googlegroups.com. > > To view this discussion visit > https://groups.google.com/d/msgid/bitcoindev/aPJ3w6bEoaye3WJ6%40console. > -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/5135a031-a94e-49b9-ab31-a1eb48875ff2n%40googlegroups.com.