Wrench attack ($5 wrench attack)
Also · $5 wrench attack · Physical attack · Coercion
The $5 wrench attack is coercion by physical threat to extract a seed phrase or force a transfer. It bypasses all cryptography by targeting the person rather than the keys.
The name comes from an xkcd comic. Rather than spend millions breaking encryption, the attacker buys a 5-dollar wrench and hits the owner until the password comes out. Applied to Bitcoin, it covers kidnappings, home invasions and threats aimed at seed phrases, hardware wallets or forced transfers. France saw a series of such attacks against crypto holders and their families in 2025 and 2026.
No key length protects against it. What helps is not being a target and not being able to comply instantly. Discretion about holdings, minimising KYC data that can leak, multisig with keys in different places, time-delayed spending and decoy wallets all raise the cost or lower the payoff. Physical security is part of self-custody, not an afterthought.
In French · Attaque à la clé à molette