Finney Attack
Security● Common
A double-spend attack named after Hal Finney. Attacker pre-mines a block containing a transaction to themselves, then makes a conflicting payment to a merchant. When merchant accepts zero-conf, attacker broadcasts pre-mined block, invalidating the payment.
Technical Notes
Requires: attacker is mining, finds block, withholds it. Risk: block becomes stale if honest block found first. Defense: wait for confirmations. Theoretical attack; requires mining capability and precise timing. More practical with significant hashrate.
Metadata
Visibility: Public
Created:1/3/2026by System