Wrench Attack

A wrench attack is coercion of the key holder rather than an attack on the key: robbery, kidnapping, extortion or threats intended to make someone hand over a recovery phrase or sign a transfer themselves. The name comes from a well-known cartoon making the point that cryptography does not help when the cheapest attack is physical. Self-custody is what creates the exposure, because an asset that moves irreversibly, with no bank to call and no transaction anyone can reverse, is worth taking by force in a way a bank balance is not. The defences are mostly behavioural: do not publish holdings, do not discuss them with people who introduced the subject, keep ownership separate from your public identity where you can, and remember that an address shared once can be watched by anyone afterwards. Arrangements that limit what can be taken under pressure — keys held in more than one place, a signer who is not present, a delay before a large withdrawal completes — reduce what a coerced signature is worth, though the honest limit is that they change what an attacker can obtain rather than whether the attempt happens. Personal safety comes before any balance.