Bitcoin developers have finished a proposed security cleanup called BIP-54, but winning enough support to activate it may prove harder than writing the code.
Key Takeaways
BIP-54 would close four Bitcoin consensus edge cases without adding new features.F2pool’s founder opposed BIP-54 on Aug. 10, complicating high-threshold miner activation.Bitcoin’s next test is a BIP-9 vote after BIP-110 stalled near block 961,635.The proposal’s authors are Antoine Poinsot, a Bitcoin Core contributor associated with Chaincode Labs, and Matt Corallo, a longtime Bitcoin developer. Corallo first raised the broader idea in 2019. Poinsot revived and expanded the work in late 2023 and early 2024, and the proposal received its formal BIP-54 designation in April 2025. The specification was marked complete in May 2026 after testing and implementation work.
The Proposal Aims to Close Four Old GapsBIP-54 would add timestamp limits at the start and end of each 2,016-block period. The rules are meant to block the classic timewarp method and a related variation known as the Murch-Zawy attack, while leaving ordinary mining unchanged.
BIP-54 Also Intends to Protect Smaller Node OperatorsBIP-54 would cap older, pre-Segregated Witness (SegWit) transactions at 2,500 legacy signature operations. Signature operations are the cryptographic checks used to prove that someone is authorized to spend bitcoin. Normal transactions use far fewer, and SegWit and Taproot transactions would not be subject to this limit. Supporters estimate the change could reduce the worst-case verification burden by about 40 times in some cases.
The third change closes a problem in Bitcoin’s Merkle tree, the system that combines transactions into one summary for each block. A transaction exactly 64 bytes long can resemble an internal piece of that structure. That creates a way to forge a proof that could mislead some simplified payment verification, or SPV, wallets into accepting a transaction that was never confirmed.
BIP-54 would simply make 64-byte transactions invalid. Those transactions have been nonstandard for years and are rarely used. The proposal’s supporters argue that banning them fixes the underlying problem more cleanly than expecting every light wallet to use a workaround.
A Final Rule Could Simplify Bitcoin’s FutureBIP-54 would require new coinbase transactions to include settings tied to the block height, or its position in the blockchain. That would guarantee uniqueness going forward and could eventually allow nodes to remove the older duplicate-transaction checks. The change could make validation simpler and support future designs aimed at reducing the storage burden of operating a full node.
F2pool’s Position Makes Activation HarderSupporters see bundling differently. They argue that every consensus change carries a high social cost, so combining several defensive fixes can reduce the number of difficult networkwide activation efforts. They also say Bitcoin’s rising value gives attackers more reason to explore weaknesses that once looked theoretical.
BIP-110’s Collapse Adds Fresh CautionThat episode does not make BIP-54 a similar proposal. BIP-54 does not add or remove general-purpose script features, nor is it a path to covenants or OP_CAT, proposals that would expand Bitcoin’s programmable spending options. Still, BIP-110 demonstrated how quickly a disputed upgrade can become a broader argument about who should decide Bitcoin’s future.
The next question is whether developers, the community, businesses, node operators, and miners can agree that fixing known but rarely exploited risks is worth another hard-fork-level coordination effort. Readers should watch for a formal BIP-9 signaling proposal, additional miner readiness announcements, and whether F2pool’s resistance prevents the broad support Bitcoin upgrades have traditionally required.
