A replay attack occurs because both the main Bitcoin chain and the new minority chain would initially accept identical transactions. If a user sells their fork-coins, the transaction could be 'replayed' on the main Bitcoin chain, effectively spending their real Bitcoin. This means that a buyer of the fork-coins could end up receiving an equivalent amount of actual BTC from the seller's wallet.
Kevin Loaec, a Bitcoin developer, highlighted this vulnerability on X (formerly Twitter), advising that large holders could be particularly targeted. He stressed that the safest course of action for those who lack the technical expertise to separate the two balances is to avoid moving their coins entirely. 'Doing nothing will be a safer option,' Loaec stated, as unmoving coins cannot be replayed due to the absence of a signed transaction to copy.
Crucially, a replay attack does not completely drain a wallet. Instead, only the specific coins put up for sale are affected, and they are spent as real Bitcoin, not the fork version. This also incurs a transaction fee on both chains, adding to the potential losses.
The underlying cause of this potential split is BIP-110, a proposal designed to exclude non-payment data, such as pictures and text, from Bitcoin transactions for a year. The implementation of such a change could lead to the creation of a minority chain, posing this replay risk to unsuspecting users.
Experts advise that until built-in replay protection is established, which may not be until early September, non-experts should exercise extreme caution. The perceived 'free money' from selling fork-coins could lead to substantial losses of legitimate Bitcoin. Therefore, for the average Bitcoin holder, patience and inaction are the recommended strategies to safeguard their assets during this period of potential volatility and technical complexity.
