Physical Security: Wrench Attacks and Precautions

Physical attacks on crypto holders skip the technology entirely. Instead of attacking a key, someone attacks the person who can move the funds, and the coercion can be as simple as a demand made in your own hallway. Crypto physical security is the discipline of making that demand less profitable and less likely to be made at all.

The category is often called a wrench attack, after the idea that the cheapest way past encryption is a threat of violence against the owner. Crypto physical security is not about locks and cameras alone; it is about what an attacker believes you can produce under pressure, and how quickly.

• Coercion targets access, not storage. Whatever you can reach in ten minutes is what an attacker will assume exists.
• Information is the first exposure. Public associations between your identity and a balance precede almost every case.
• Time locks convert a demand into a delay. Structure that cannot be rushed is the most useful defence.
• Compliance first, resistance never. Physical safety outranks every balance.

What a wrench attack actually is

It is a robbery with a technical pretext. The attacker does not need to understand your setup, only to believe you can transfer funds, and only to apply enough pressure to make transferring faster than refusing.

Why coercion works

Because it is fast. A signature takes seconds, and the attacker’s leverage is entirely about compressing your decision time. Everything that slows the transfer, or reduces what a single transfer can reach, works against that leverage.

Who becomes a target

People whose holdings are known or suspected, usually through public association rather than confirmed balances. Speaking at events, posting portfolio screenshots, receiving large transfers to an address linked to your name, or appearing in a public list of holders all create the association. The attacker rarely needs an exact figure; a plausible guess is enough motivation.

Crypto physical security as a design problem

The useful framing is architectural. Assume a demand will be made and design what happens next, rather than assuming you will think clearly in the moment.

The first design decision is separation. A wallet you can access quickly should hold an amount you would hand over without a second thought. Funds that require a hardware device, a second person, or a delay should be structurally unreachable in a single sitting. This is not deception for its own sake; it is the difference between a loss and a catastrophe.

The second is delay. Multisignature arrangements with a co-signer who is not physically present, and time-locked withdrawals, both convert an immediate demand into a negotiation the attacker cannot win quickly. The delay has a cost: it also slows you down in an emergency, and it requires planning before you need it.

Both decisions should be written down, because a plan that exists only in your head is a plan you will improvise. A single page stating what is accessible, who holds the other key, and whom to call is enough.

The best outcome in a physical incident is that you can hand over something, the attacker leaves, and the amount is one you had already decided was expendable. Everything else is a plan built on the assumption that you will perform well under threat.

Comparing exposure and mitigation

A crypto physical security checklist

Work through this once, then review it annually or after any change in circumstances. The order reflects effort against benefit.

1. Decide the amount you would surrender without hesitation, and keep only that in an immediately accessible wallet.
2. Move the remainder behind a hardware device, a multisignature arrangement, or a time lock that cannot be completed alone.
3. Remove your home address from people-search sites and use a separate mailing address for anything financial.
4. Stop publishing balance screenshots, portfolio percentages and holdings comparisons on accounts linked to your name.
5. Tell one trusted person where the recovery material is and how to reach it, and nothing more widely than that.
6. Agree a household response: comply, do not resist, and call emergency services once it is safe.
7. Review travel plans and carry only what the trip requires.
8. Rehearse the response once, out loud, so the first time you say it is not the first time you have thought it.

If an incident happens

Comply. Physical safety is the only priority in the moment, and no balance is worth an injury. Resistance increases the chance of harm without protecting the funds, because a determined attacker with time will get what is reachable.

Afterwards, treat the transferred funds as gone and focus on the remaining accounts. Move whatever the attacker did not reach, revoke approvals, and change credentials from a device that was not present. Then report to local police; the report is also what insurers, venues and, in some jurisdictions, tax authorities will ask for.

Expect the aftermath to be administrative and slow. Document what was taken, when, and by whom if known, and keep it in one place. Rules on reporting, insurance and tax treatment differ by jurisdiction, so confirm the local requirements rather than relying on general guidance.