Replay attack fears grow as BIP-110 backers plan RDTS fork

Backers of the stalled BIP-110 fork are discussing a restart that has renewed concern about replay attacks on two blockchains that would share the same transaction history.

The BIP-110 minority branch briefly produced blocks on Aug. 8 and reached block height 961,636, but miner signaling peaked at about 2.53% and the chain stalled after two immediate blocks. Supporters now propose changing the minority chain’s proof-of-work to BLAKE2b and reviving the network under the name RDTS. Developers working on Bitcoin Knots plan to add a new sighash option that would let users create transactions valid on RDTS but invalid on the dominant Bitcoin chain; that protection would be opt-in rather than mandatory.

A replay attack occurs when a single signed transaction is valid on both chains that share pre-split history and signature rules. If an owner holds one bitcoin before a split, the same unspent output exists on each chain afterward. If the same signed transaction is accepted by both networks, a third party can copy and rebroadcast it on the other chain and move the matching funds without the owner’s private key being revealed.

Mempool.space developer Mononaut wrote that many of the minority chain’s blocks have replayed older transactions from the main chain. Under the approach discussed for RDTS, ordinary transactions would remain compatible with Bitcoin Core sighash types and so could be replayable across chains. Users seeking protection would need wallets or hardware that support the new RDTS-specific sighash or would have to split coins manually by creating transactions that one chain accepts and the other rejects.

Luke Dashjr argued that replay protection should be the minority chain’s responsibility, writing, “Replay protection was Spamcoin’s responsibility since it’s the airdrop altcoin,” and adding that “legitimate Bitcoin transactions need to remain valid on Bitcoin.” Dashjr has repeatedly described the dominant SHA-256d chain as an altcoin while calling the BIP-110 branch the legitimate Bitcoin.

Some users on social media questioned the plan and potential exchange support. One user wrote, “I guess it won’t be listed on exchanges then.” Another cautioned that spreading misleading claims could cause financial harm to holders.

If backers proceed with a BLAKE2b fork around early September, decisions about replay protection will determine whether holders can safely separate assets that share the same pre-split history. Exchanges, wallet developers and hardware-signing firmware vendors would need to decide whether to support the new sighash type for opt-in protection to be effective.