COLDCARD Mk5

The COLDCARD Mk5 is a Bitcoin-only signing device from Coinkite, which says its devices are designed and assembled in Canada. Coinkite introduced it on 10 March 2026. It has a numeric keypad, a 1.54-inch screen behind Gorilla Glass, two secure elements and three ways to move data: USB-C, NFC and a microSD slot. It was listed at $219, marked down from $269, on Coinkite’s store on 14 October 2026. This page is built from Coinkite’s documentation and advisories; we have not used the device.

Who is the COLDCARD Mk5 for?

It is built for people who hold only bitcoin and already know which wallet software they want. Coinkite’s product page says there is “No COLDCARD account or required companion app”, and its setup guide walks through Sparrow Wallet as the coordinator (the program that tracks balances and builds transactions). The Mk5 supports BIP-39 passphrases and multisig wallets.

It is a weaker fit if you:

• hold coins other than bitcoin, since Coinkite describes itself as a Bitcoin-only company;
• want a maker app that guides setup and shows balances;
• want to sign by QR code: the setup guide says the Mk5 can show QR codes but “has no camera”, so it cannot scan them (the COLDCARD Q has one);
• want a battery: the guide says the Mk5 “has no internal battery” and needs USB-C power the whole time it is on.

What changed from the COLDCARD Mk4?

The changes are hardware. Coinkite’s Mk5 vs Mk4 page lists a new 1.54-inch screen, a redesigned keypad, a USB-C port moved to the bottom edge, faster and more reliable NFC with the tap point in the top-right corner, and a tougher case. The launch announcement adds a choice of colours. The Mk5 vs Mk4 page says the Mk5 “runs exactly the same firmware image as Mk4”, with the same pair of secure elements.

Coinkite’s spec sheet gives the Mk5 as 87 x 52 x 10.3 mm with its cover on and approximately 55 g, against 88 x 52 x 10 mm and about 30 g for the Mk4.

Is the COLDCARD Mk5 air-gapped?

It can be used without a data cable. The setup guide recommends a microSD card as the signing method, and Coinkite’s microSD signing guide describes the round trip: the coordinator saves an unsigned transaction in the PSBT format (BIP-174) to the card, you move the card to the Mk5 for review and signing, and the Mk5 writes the signed PSBT back to the card for the coordinator to load and broadcast. Coinkite’s NFC guide, which covers the Mk5 and the Q, describes a tap link of about 4 centimetres and says “NFC is disabled by default”. Power still comes over USB-C. Our air-gapped wallets guide covers the trade-offs.

Does the COLDCARD Mk5 have a secure element?

Two, from different vendors: a Microchip ATECC608 and a Maxim DS28C36B, which Coinkite says protect the master secret. The product page also describes firmware signatures checked at boot, shown by a green or red light, and a clear case meant to make physical implants visible. The setup guide’s two-part PIN shows anti-phishing words after the first half, and 13 wrong attempts permanently brick the device; “there is no way to recover a forgotten PIN”. Trick PINs include a duress PIN and a “Brick Me” PIN that destroys the secure elements. Our records include no security certification level for either chip.

Is COLDCARD open source?

The firmware source is public on GitHub under MIT plus the Commons Clause, which withholds the right to sell the software. The Open Source Definition does not allow that restriction, so the code is source-available: anyone can read and audit it, but the licence limits commercial reuse. COLDCARD vs Trezor compares Trezor’s approach.

How do you back up a COLDCARD Mk5?

The setup guide offers a 12- or 24-word BIP-39 seed, and requires your own randomness first: at least 65 key presses with unpredictable timing, 50 fair physical dice rolls or 128 physical coin flips. BIP-39 words restore in other compatible wallets. An optional passphrase creates a separate wallet from the same words; lose the passphrase and you lose that wallet.

From firmware 5.6.3, Coinkite’s codex32 page lists the Mk5 among models that can generate and import codex32 secrets and Shamir shares. Codex32 (BIP-93) is not SLIP-39, and we found no native SLIP-39 support documented for the Mk5. The product page also lists encrypted backups, Seed XOR and BIP-85. Our seed phrase guide compares the formats.

What happened with the COLDCARD seed-generation bug?

On 30 July 2026 Coinkite published an advisory stating that a firmware bug weakened seed generation on several COLDCARD models and that attackers regenerated private keys from weak seeds offline and stole funds; the devices were not remotely accessed. On the Mk5, seeds generated before standard firmware 5.6.0, or Edge firmware 6.6.0X, are affected; the advisory puts Mk4 and Mk5 seeds from those releases at about 72 bits of entropy rather than the expected 128. Seeds made with at least 50 fair, independent dice rolls that were never recorded or exposed are not considered at risk from this issue alone.

What Coinkite tells owners:

• Updating firmware does not repair an existing seed. Update, create a new seed on fixed firmware, verify the backup, send a small test, then move the rest.
• A strong, unique BIP-39 passphrase reduces the immediate exposure but does not repair the affected seed; passphrase users should also migrate.
• Keep the old backup until the move is confirmed.

Coinkite’s security status page, revised on 1 October 2026, lists 5.6.3 as the current standard release for the Mk4 and Mk5. The setup guide tells new owners to check that page and install the recommended firmware before creating or importing a seed.

What we could not verify

• The screen’s resolution. Coinkite’s setup guide identifies the display as a monochrome LCD but gives no pixel count.
• A certification level for either secure element.
• Which firmware version new units ship with.
• Which mobile wallets support NFC signing; Coinkite’s guide names only Nunchuk.
• How the July 2026 losses split by model.

How we source these facts: methodology.