Guides / Glossary / Hardware signing device
Glossary

Hardware signing device: keeping keys off ordinary computers

A device dedicated to holding a key and signing, so the key never sits on a general purpose computer.

Education only

Definition. A device dedicated to holding a key and signing, so the key never sits on a general-purpose computer.

How it works

A hardware signing device, often sold as a hardware wallet, generates a private key internally and keeps it there. The computer or phone running the wallet software prepares an unsigned transaction and sends it to the device. The device shows the key details on its own screen, waits for the holder to approve with a button or PIN, signs inside the device and returns only the signature. The private key never leaves.

Devices differ in how they connect (USB, QR code, memory card, Bluetooth or NFC), whether they use a secure element chip, whether their firmware is open source, and whether there is a bitcoin-only edition. The site's hardware page compares published facts about several devices without ranking them.

Why it matters for a company

Ordinary office computers are exposed to email attachments, browser extensions and malware. Keeping a company's keys on dedicated devices removes the most common attack route. The screen on the device also gives each signer a trusted place to check the destination and amount, which is the main defence against address swapping malware.

For multisig, many companies deliberately use devices from two or three different makers. A design flaw or firmware bug in one brand then affects only one key, not the threshold. The 2026 COLDCARD seed advisory, described by the maker as a firmware weakness in affected versions, shows why firmware notices need an owner in the company.

Example only, fictional. A company buys three devices from three makers, directly from each manufacturer, records serial numbers and firmware versions in the key register, and puts a quarterly calendar reminder on the finance director to check each maker's security page.

Common mistakes

Sources

Primary sources only. Each link was checked on 9 November 2026. Rules change, so confirm the current version with your adviser.

  1. Bitcoin developer documentationWallets guide: signing-only wallets and hardware wallets
  2. CoinkiteCOLDCARD security advisory: weakened seed generation in affected firmware (July 2026)
  3. Bitcoin BIPsBIP 174: Partially Signed Bitcoin Transaction format (PSBT)
Education, not advice.

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Rules change. This information is correct to our understanding at the last-reviewed date, but it may be incomplete or out of date, and official sources take precedence. Bitcoin is volatile. A company that buys it could lose some or all of the money it puts in.

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