Subject: Re: [bitcoindev] Re: Make pathological transactions with more than 2500 legacy signature operations non-standard

From: "'Antoine Poinsot' via Bitcoin Development Mailing List" <[email-masked]>
Date: Mon, 07 Jul 2025 21:46:58 +0000

This limit only concerns legacy signature operations. Off-chain constructions use Segwit inputs, as they would be trivially broken by txid malleability otherwise.

On Friday, July 4th, 2025 at 10:38 AM, Antoine Riard <[email-masked]> wrote:

> Hi Poinsot,
>
> Thanks for the collection of historical txn hitting the proposed new limit.
>
> The only long-term downside coming immediately out of mind, if the rule becomes consensus
> in the future, it's the implicit limitation it would make on the multi-party dimensions
> of off-chain constructions. In the past, I made really rough math for 1000-sized participants
> payments pools, where for the funding_tx, you have the 1000 participants contributing
> one input with one sig for each [0].
>
> In my understanding the new limit of 2500 signatures operation would make a hard-limit
> for the number of participants entering in such construction, without other tricks that
> are consuming more block space. One can note the downside on funding tx of high-order
> off-chain construction, if a max tx size consensus limit is introduced in the future.
>
> Of course, I do not deny the DoS rational of introducing the 2500 sig limit and it's
> very needed. At the same time, we should be careful of not closing too much doors for
> future off-chain constructions and long-term tx throughput scalability.
>
> I do believe, it's always technically possible in the future to introduce new opcode
> or segwit versions scripts (e.g grafroot or entroot-based pool construction), which
> wouldn't be subject to the new limit, and as such more scalable. If I'm correct, I
> think it's all about how the limit is implemented to parse current scripts to be
> spent.
>
> But it's hard to say without code available to review and reason. May I kindly note
> there is no reference implementation attached in the current BIP54 document [1]. Even,
> if it's often updated, it's always fruitful to have code under the eyes for review.
>
> This might be the kind of concern (very) far down the line...but preserving the
> evolvability of the consensus rules is a good property to care about, in my humble
> opinion.
>
> Best,
> Riard
> OTS hash: a2bb9a1faf79309b039d8ae7e0b951644ca0adb2
>
> [0] https://gnusha.org/pi/bitcoindev/[email-masked]/
> [1] https://github.com/bitcoin/bips/blob/master/bip-0054.md
>
> Le mercredi 2 juillet 2025 à 09:54:33 UTC+1, Antoine Poinsot a écrit :
>
>> Hi everyone,
>>
>> To mitigate high block validation time, BIP54 proposes to make transactions which require more than
>> 2500 legacy signature operations invalid by consensus. The 2500 figure was chosen as the tightest
>> value that did not make any non-pathological currently standard transaction invalid.
>>
>> No transaction in Bitcoin's history would have both hit the BIP54 sigop limit and been standard
>> according to today's Bitcoin Core policy[^0]. But what happened in the past doesn't matter as much
>> as the fact that it is possible today to create a pathological standard transaction that is
>> BIP54-invalid.
>>
>> This opens up a major DoS vector against unupgraded miners if BIP54 ever gets activated in these
>> conditions. Therefore i propose to make such transactions non-standard and hold off activation of
>> BIP54 until we have good reasons to believe that the vast majority of the hashrate won't create a
>> block containing such a transaction.
>>
>> Doing so gives better guarantees in case BIP54 is ever considered for activation, and comes at
>> virtually no cost since these pathological transactions have never been used and serve no purpose
>> beyond increasing the cost of validation. Bitcoin Core PR #32521 implements this change, which i
>> hope to get into the upcoming 30.0 release as well as backported to previous versions.
>>
>> Best,
>> Antoine Poinsot
>>
>> [^0]: Here the full list of historical transactions that would have hit the BIP54 sigops limit:
>> - 659135664894e50040830edb516a76f704fd2be409ecd8d1ea9916c002ab28a2
>> - bea1c2b87fee95a203c5b5d9f3e5d0f472385c34cb5af02d0560aab973169683
>> - 24b16a13c972522241b65fbb83d09d4bc02ceb33487f41d1f2f620b047307179
>> - 53666009e036171b1aee099bc9cd3cb551969a53315410d13ad5390b8b4f3bd0
>> - ffc178be118bc2f9eaf016d1c942aec18441a6c5ec17c9d92d1da7962f0479f6
>> - 2f1654561297114e434c4aea5ca715e4e3f10be0be8c1c9db2b6f68ea76dae09
>> - 62fc8d091a7c597783981f00b889d72d24ad5e3e224dbe1c2a317aabef89217e
>> - d939315b180d3d73b5e316eb57a18f8137a3f5943aef21a811660d25f1080a3f
>> - 8a6bfaa78828a81147e4848372d491aa4e9048631982a670ad3a61402a4ec327
>> - 02cc78789cc070125817189ec378daa750355c8b22bbce982ed96aa549facb1f
>> - b97a16ae2e8ae2a804ed7965373b42055f811653f4628e4bef999145d4b593bc
>> - c51ffaf08188859669571f897f119b6d39ea48a9334212f554bf4927401b71f3
>> - 33ccdda65abdda8025adb03841410dda5fa8948bd38b7fbaf3fed521daf5c4d3
>> - bb41a757f405890fb0f5856228e23b715702d714d59bf2b1feb70d8b2b4e3e08
>> - ba588134ecc93fdbfa06f795c9bf7a05b09ca9ca9095659e401325d501a90363
>> - ba6c6d2389f765f7873f5a9a7c11bf806afd784d15b0b8dff011fe95d1d5e841
>> - dd49dc50b54b4bc1232e4b68cfdd3d349e49d3d7fe817d1041fff6dd583a6eaf
>> - 3d724f03e8bcc9e2e3ea79ebe4c6cffca86d85e510742cd6d3ac29d420787a34
>> - 8bcf8e8d8265922956bda9b651d2a0e993072c9dca306f3a132dcdb95c7cee6e
>> - ba31c8833b7417fec9a84536f32fcb52d432acb66d99b9be6f3899686a269b2b
>> - 9cc0a350d50fa252264636e62d586c7121d0a5656bc7e6b27354325684bec007
>> - dd5e32971010ef0c9f4cda8977830d727a6828165c69005a3fab67415c755b7d
>> - 66be4e766df2c23e08f4cf8c3e6cfa202b20967616ace38e1cbc1f20ee78db2e
>> - e229a83deafec5f49e4990dba914fd815d05809f5eefbd979d55fb64f93827a3
>> - 901e3695838925dd020a085e8f078c393e64179dcf0a43134a1547d21acab49a
>> - 49ab4d05adbc3294fbbd63d3b876fb97a87a3f5090aa6b1d87f31ab1c4564235
>> - c4f4357657ba403455167b2897acfcb922c2a0973c34e58733ca352394e6c629
>> - 6c3ee29a9b584fbeae60169f0abce573a7b768bf21398d4dfad9011aa7132530
>> - 5dc2bdc5ce29c52840f10203fd93ffed82da4cf49eddf93437dd1329baa9ade5
>> - f40fd92f5e8cecf956caec4b6abe0b88decafde0ae71d16a72c41cb1a3da0d60
>> - 92b68e4a19ef47c0dd022727a9c4b8ceb9466ce752ad8995ffbc5948bdfabf57
>> - 1b604a075075197c82d33555ea48ae27e3d2724bc4c3f31650eff79692971fb7
>> - 5d8875ed1707cfee2221741b3144e575aec4e0d6412eeffe1e0fa07335f61311
>> - 14dd70e399f1d88efdb1c1ed799da731e3250d318bfdadc18073092aa7fd02c2
>> - bb75a8d10cfbe88bb6aba7b28be497ea83f41767f4ee26217e311c615ea0132f
>> - a684223716324923178a55737db81383c28f055b844d8196c988c70ee7075a9a
>> - fa9120afe1bb09b7154ba82a022cbdcc29fc5be2699b346ebb7ffdc46807b2f7
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>> - d85ce71f583095a76fb17b5bb2a1cbf369e2a2867ca38103aa310cbb2aaf2921
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>> - cb550c9a1c63498f7ecb7bafc6f915318f16bb54069ff6257b4e069b97b367c8
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>> - 9fdbcf0ef9d8d00f66e47917f67cc5d78aec1ac786e2abb8d2facb4e4790aad6
>> - 9c667c64fcbb484b44dcce638f69130bbf1a4dd0fbb4423f58ceff92af4219ec
>> - 2e7c454cfc348aa220f53b5ba21a55efa3d36353265f085e34053c4efa575fda
>> - 484c8f9d1adf16a576bce52721a5e4edd5239df346d94fd730f6d7b681ab3652
>> - e3d3d1ecec5d6b57792c793c413fc9b19189f5b932db8887d46f06abc101d24e
>> - b23c99c30339cb93eb04790bc5213f7732365488fe2549802bb472084b6ec508
>> - 92f217ec13ab309240adc0798804b3418666344a5cbfff73fb7be8192dad5261
>> - 22e861ee83c3d23a4823a3786460119425d8183783068f7ec519646592fac8c2
>> - fa5a58f787f569f5b8fab9dadb2447161fac45b36fb6c2c0f548ed0209b60663
>> - 767885bc144bdc0414217547f0169352a065083750371cabe5acbd0e0dd60436
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>> - 9db4e0838c55ef20c5eff271fc3bf09a404fff68f9cdad7df8eae732500b983d
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>> - 9c972a02db30f9ee91cc02b30733d70d4e2d759b5d3c73b240e5026a8a2640c4
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>> - e32477636e47e1da5fb49090a3a87a3b8ff637d069a70cd5b41595da225e65b4
>> - a7e0a86944e9750a3fe372dd318da7b81c4f4c4ab228741ba0cf7fb6d56d6640
>> - f62f2c6a16b5da61eaae36d30d43bb8dd8932cd89b40d83623fa185b671c67f9
>> - 856a2117b6d81acbe6add60a114307d9572dff027079151d50ee77a7b0c70404
>> - 763e13f873afa5f24cd33fc570a178c65e0a79c05c88c147335834fc9e8f837b
>> - c3f2c2df5388b79949c01d66e83d8bc3b9ccd4f85dbd91465a16fb8e21bf8e1b
>> - e245f6c3c6b02dc81ea1b6694735565cc535f603708783be027d0e6a94ac3bd5
>> - 02313ac62ca8f03930cdc5d2e437fabc05aea60a31ace18a39678c90b45d32bd
>> - 01d23d32bccc04b8ca5a934be16da08ae6a760ccaad2f62dc2f337eee7643517
>> - d985c42bcd704aac88b9152aede1cca9bbb6baee55c8577f84c42d600cfec8e4
>> - 6bb39576292c69016d0e0c1fe7871640aab12dd95874d67c46cf3424822f8dfd
>> - 79e30d460594694231f163dd79a69808904819e2f39bf3e31b7ddc4baa030a04
>> - 26ed04bd772c7d3d621329bda8eefec9f81108d46ef0bd3b690000465f5254b3
>> - bf40393fedc45a1b347957124ef9bb8ae6a44feecee10ef2cc78064fabf8125f
>> - 446c0a1d563c93285e93f085192340a82c9aef7a543d41a86b65e215794845ef
>> - 1cf52f9ef89fa43bb4f042cbd4f80e9f090061e466cbe14c6b7ba525df0e572e
>> - 54bf51be42ff45cdf8217b07bb233466e18d23fd66483b12449cd9b99c3a0545
>> - b5ca68205e6d55e87bd6163b28467da737227c6cbcc91cb9f6dc7b400163a12b
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>> - 4eba5deb2bbf3abf067f524484763287911e8d68fb54fa09e1287cf6cd6d1276
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>> - 1e700d8ce85b17d713cad1a8cae932d26740e7c8ab09d2201ddfe9d1acb4706c
>> - b8ba939da1babf863746175b59cbfb3b967354f04db41bd13cb11da58e43d2a8
>> - 22df2138a28c9d339813854a38181ffc5ac6f37d171d5b5bd6b0b79bf8d3c641
>> - 1d93bfe18bc05b13169837b6bc868a92da3c87938531d6f3b58eee4b8822ecbf
>> - e0c5e2dc3a39e733cf1bdb1a55bbcb3c2469f283becf2f99a0de771ec48f6278
>> - c1e00054cc3fef88c2fdec2967e96fdb4c645bcf3f08b0580b51e47ecbfab71a
>> - 9a567fde7c65bf85bbc2b109277933431ebc8a35de321a4b6436601d68aa4521
>> - 6a9263e48a076bfc37deb93d01bf354305f4ac929be6b0ca05c078381a562c0c
>> - 0683fb9cfcd4a211c14ef7cd2d03739160ff9ba1cb5396be227e475e932a8e9b
>> - 2290263dddf8f06f099fcfb130a85f8f00b6cc1e05565a4c028d2187c8592d15
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>> - b28d67131d00bda9dac0da484dd1352c55ec6a869ea04a7e85b71d2ddf2356d9
>
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