COLDCARD

What is COLDCARD?

COLDCARD is a range of hardware walletsGlossaryHardware walletA small dedicated device that keeps your private keys offline and signs transactions internally. The key never leaves the device, so malware on your computer can’t get at it.On the learning path: Stage 6 · Step 1 – Hardware wallets compared →In the glossary →× from Coinkite, founded in Toronto in 2012; the devices are developed and assembled in Canada.^[2] Coinkite currently sells the COLDCARD Q with a large display, keyboard and QR scanner, and the compact Mk5 with a number pad. Both are built for Bitcoin only and use two secure elementsGlossarySecure element (security chip)A chip specially hardened against physical attacks, like the ones in bank cards and passports. In many hardware wallets it protects the PIN and secrets if the device falls into the wrong hands.On the learning path: Stage 6 · Step 1 – Hardware wallets compared →In the glossary →× from different manufacturers (Microchip and Maxim).^[1]

Features

• Signing without a cable (air gapGlossaryAir gapAn air-gapped signing device has no cable or wireless connection to other devices. Transactions travel back and forth by QR code or memory card – so the private key stays completely offline.On the learning path: Stage 6 · Step 1 – Hardware wallets compared →In the glossary →×): transactions are passed via microSD card, NFC or – on the Q – QR code.^[1]
• Protection against coercion (wrench attackGlossaryWrench attack ($5 wrench attack)An attack using violence or threats instead of technology: criminals force Bitcoin owners to unlock their wallet or transfer bitcoin. The best protection is discretion – if nobody knows you own bitcoin, you are less likely to become a target.On the learning path: Stage 6 · Step 2 – Spotting scams →In the glossary →×): one PIN opens a decoy wallet, another makes the device unusable.^[1]
• Works with software wallets such as SparrowProvider · Software walletSparrow WalletBitcoin desktop wallet with no purchase price and full transparency: coin control, PSBT, multisig and support for most hardware wallets.Non-custodial software – no financial licence required · reviewed Sept 2026Price: no purchase price (donations welcome); network fee when sending (as of Sept 2026)On the learning path: Stage 5 · Step 2 – Setting up your first wallet →Our profile →Official website ↗×, NunchukProvider · Software walletNunchukMultisig wallet for smartphone and desktop – no subscription if you do it yourself, subscriptions for assisted multisig and inheritance.Non-custodial software – no financial licence required · reviewed Sept 2026Price: Basic version $0; subscriptions $120 to $2,100 a year (as of Sept 2026)On the learning path: Stage 5 · Step 2 – Setting up your first wallet →Our profile →Official website ↗× or Specter, including for multisigGlossaryMultisig (multi-signature)A wallet in which several keys jointly control the bitcoin – for example 2 of 3. If one key is lost or stolen, the bitcoin stays safe. In return, setting it up and backing it up is considerably more demanding.On the learning path: Stage 6 · Step 4 – Inheritance & emergency plan →In the glossary →×.^[1]

Prices (as of September 2026)

Coinkite lists the Q at $319 and the Mk5 at $219 – promotional prices instead of the regular $369 and $269. USB cables are not included, and the Q comes without batteries.^[4] If you buy directly from Coinkite in Canada, import charges may apply in the EU, the UK or Switzerland. Coinkite also lists resellers in several European countries, including Germany, France, the Netherlands and Switzerland.^[5]

Open code, restricted licence

Coinkite describes the firmware as open source and reproducible: advanced users can check what runs on the device.^[1] However, the licence (MIT with a ‘Commons Clause’) prohibits selling products or services whose value derives substantially from this code – strictly speaking, that is not open source but publicly viewable code.^[3]

Security warning, July 2026

On 30 July 2026 (updated 1 August 2026), Coinkite warned that a firmware bug had weakened the randomness used to generate new seeds – on the Mk4, Mk5 and Q to around 72 bits instead of 128, and even more on the older Mk2/Mk3.^[7],[6] Attackers recomputed the private keys offline and stole funds; the devices themselves were not taken over remotely.^[6]

Seeds generated with this firmware are affected:^[7],[6]

• Mk2/Mk3: firmware 4.0.1 to 4.1.9
• Mk4/Mk5: before 5.6.0 (Edge firmware before 6.6.0X)
• Q: before 1.5.0Q (Edge firmware before 6.6.0QX)

A firmware update does not repair a seed that has already been generated. Coinkite advises affected users to update the firmware, generate a new seed, check the backup and a receive address, send a test transaction and only then move the funds – without rushing, and keeping the old backup until the move is complete.^[7] A strong, unique BIP-39 passphraseGlossaryPassphrase (the ‘25th word’)An extra word of your choice added to your seed phrase. The same words then produce a completely different wallet. This protects you if someone finds your words – but if you forget the passphrase, access is lost for good.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× reduces the immediate risk but does not replace the move. The only seeds not considered at risk from this bug are those created with at least 50 fair, independent dice rolls added, whose sequence was never written down or disclosed.^[7],[6]

For the Mk2/Mk3, 4.2.0 is the final firmware; Coinkite recommends moving long-term custody to a current Mk4, Mk5 or Q.^[6] According to the shop, new devices ship with corrected firmware; Coinkite still advises updating as soon as you receive one.^[4] Devices that are easier to use for getting started are covered in Hardware wallets compared.