Bitcoin Holders Warned of Replay Attack Risk From Possible BIP-110 Fork

A potential Bitcoin chain split tied to the controversial BIP-110 proposal could expose holders to losing real bitcoin if they try selling coins from the new fork, according to developer Kevin Loaec.

How the Risk Works

If bitcoin splits into two chains this weekend, holders would end up with identical balances on both chains. Since both chains initially accept the same signed transactions, selling fork coins to a buyer could allow that buyer to replay the same transaction on the actual bitcoin chain, effectively taking the seller’s real BTC as well. Loaec warned large holders could be targeted first, and said doing nothing is the safest approach since coins that never move can’t be replayed.

What’s Driving the Potential Split

The situation stems from BIP-110, a proposal aimed at keeping non-payment data out of bitcoin transactions for a year. While the standard miner-approval threshold of 55% hasn’t been reached, the proposal includes a fallback: starting around block 961,632 this weekend, nodes running BIP-110 software will reject any block lacking the required marking, regardless of miner consensus. Since nearly all current mining power doesn’t include that marking, a minority chain split becomes possible, though not guaranteed, especially with signaling currently near just 2.6%.

No Automatic Protection Yet

Replay protection built into BIP-110 doesn’t activate until block 965,664, expected around early September, meaning holders would need to manually separate their coins before spending safely in the meantime.