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
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