"" Replay Attack Raises Concerns for BIP-110 Hard Fork
A planned revival of the failed BIP-110 stalled fork is putting an old cryptocurrency hazard back in the spotlight: replay attacks, where a transaction intended for one blockchain can potentially be copied onto another.
The issue matters because BIP-110 supporters are discussing a hard fork that would replace the minority chain’s SHA-256d mining algorithm with BLAKE2b. Such a move would permanently create a whole new design, but the two networks would still share their transaction history from before the split.
Imagine someone holds 1 bitcoin before a hard fork. When the blockchain divides, the same historical unspent transaction output, or UTXO, exists on both networks. In practical terms, the owner controls corresponding coins on each chain with the same private key.
Trouble begins if both networks also recognize the same transaction and signature rules. Suppose the owner sends the coin to an exchange on Chain A. If that signed transaction is also valid on Chain B, another party can copy it and broadcast it there. Chain B may accept the transaction because, cryptographically, nothing distinguishes the authorization from one intended for its network.
That is a replay. Nobody steals the private key or breaks Bitcoin’s cryptography. The problem is simpler: the user created one valid authorization, but two blockchains recognize it.
The emerging plan for BIP-110 does not appear to provide automatic, comprehensive two-way replay protection. Instead, at least according to Discord discussions, Bitcoin Knots is implementing a new sighash option that can create a transaction valid on the RDTS chain but invalid under Bitcoin Core.
BIP-110 supporter Luke Dashjr has taken an unusual position on which network should bear responsibility for replay protection. He has argued that “legitimate Bitcoin transactions need to remain valid on Bitcoin.” His reasoning rests on his assertion that the BIP-110/RDTS minority network is Bitcoin, while the overwhelmingly dominant SHA-256d Bitcoin blockchain is the breakaway network.
However, the majority network retained essentially all meaningful Bitcoin hashrate, the longest chain, weight of work, liquidity, and economic recognition. The BIP-110 proposal was subsequently marked closed, while supporters moved toward plans for a BLAKE2b proof-of-work change intended to revive the minority network.
The Bitcoin community is frustrated with Dashjr’s repeated claims and the intended opt-in styled replay protection being discussed is a bone of contention. “Lol. Luke isn’t gonna launch his sh**coin with replay protection, is he? I guess it won’t be listed on exchanges then,” one X user wrote on Wednesday.
The Future of Replay Protection for BIP-110
If the BLAKE2b fork proceeds around Sept. 1, replay protection will therefore be more than an obscure technical detail. It will become a critical issue for wallets, exchanges, and holders. Infrastructure providers, particularly crypto exchanges, are unlikely to touch a chain that chooses opt-in protection over a universal replay barrier.
The decision is strange, especially for a new chain and crypto asset with zero exchange support. The outcome will depend on how the BIP-110 community handles replay protection. Will they implement a universal barrier or continue with an opt-in approach? Only time will tell.
