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

From: "'Antoine Poinsot' via Bitcoin Development Mailing List" <[email-masked]>
Date: Wed, 02 Jul 2025 08:47:54 +0000

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
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    - bb41a757f405890fb0f5856228e23b715702d714d59bf2b1feb70d8b2b4e3e08
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    - ba6c6d2389f765f7873f5a9a7c11bf806afd784d15b0b8dff011fe95d1d5e841
    - dd49dc50b54b4bc1232e4b68cfdd3d349e49d3d7fe817d1041fff6dd583a6eaf
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