[Wallets](https://revain.org/wallets/) › COLDCARD

# COLDCARD: keys, security, fees and reviews

## In short

- **Key control**: Self-custody: private keys stay offline on the device and transactions are signed without the keys touching the internet.
- **Fees**: Device price: List price COLDCARD Q $369, COLDCARD Mk5 $269 in the official store (as of 31 October 2026); a one-day discount was running.
- **Risks and caveats**: Seeds created on affected firmware before July 2026 remain weak after a firmware update; funds must be moved to a newly generated seed.
- **Checked**: 31 October 2026

## Key facts

- **Official site**: [coldcard.com](https://coldcard.com/)

Key facts checked on 31 October 2026 against official sources.

## What is COLDCARD

COLDCARD is a Bitcoin-only hardware wallet made by Coinkite Inc. of Toronto, Canada (founded 2012). The current models are the COLDCARD Q, with a QWERTY keyboard and QR scanner, and the smaller Mk5. It signs transactions air-gapped through MicroSD, QR or NFC and works with third-party wallet software instead of a required companion app.

## Who holds the keys

| Parameter | Details |
|---|---|
| Key control | Self-custody: private keys stay offline on the device and transactions are signed without the keys touching the internet. |
| Account model | No COLDCARD account or companion app needed; works with coordinator software such as Sparrow, Nunchuk or Specter. |
| Seed phrase | BIP-39 seed words (24); optional passphrase, encrypted MicroSD backups, Seed XOR and, since September 2026, Codex32 and Shamir backups. |
| Recovery | Support never asks for seed words, passphrases, dice rolls or backup files. |

## Features and supported networks

| Parameter | Details |
|---|---|
| Supported networks | Bitcoin only. |
| Connectivity | QR (Q only), MicroSD, NFC, USB-C and virtual disk; all are off by default. |
| Secure element | Two secure elements from different vendors: Microchip ATECC608 and Maxim DS28C36B. |
| Display | Q: 3.2-inch LCD with full keyboard and AAA battery option; Mk5: 1.54-inch Gorilla Glass screen with numeric keypad. |
| Multisig | Multisig, descriptor export, BIP-85 child seeds, duress and brick-me PINs, temporary seeds. |

## Security and audits

- Firmware source is public on GitHub (Coldcard/firmware) under MIT terms plus the Commons Clause, which restricts selling the software; builds are reproducible since firmware 4.0.0 (March 2021).
- No Common Criteria or other certification is claimed for the two secure elements (Microchip ATECC608, Maxim DS28C36B).
- Coinkite's advisory of 30 July 2026 disclosed a firmware bug that weakened seed generation; attackers regenerated keys of affected seeds offline and stole funds. Mk2/Mk3 firmware 4.0.1-4.1.9 was most affected; Mk4, Mk5 and Q seeds made before the fixes had about 72 bits of entropy instead of 128.
- Fixed firmware exists for every model (Mk2/Mk3 4.2.0, Mk4/Mk5 5.6.0, Q 1.5.0Q and later), but updating does not repair an existing affected seed; owners must move funds to a new seed unless the dice-roll exception applies.
- Independent reviewers made targeted checks of the fix; Coinkite states this is not a complete audit of every firmware binary.

## Security incidents

| Date | What happened | Source |
|---|---|---|
| 30 July 2026 | Exploit: Coinkite disclosed a firmware bug that weakened seed generation (Mk2/Mk3 firmware 4.0.1-4.1.9 most affected; Mk4, Mk5 and Q seeds before the fixes had about 72 bits of entropy). Attackers regenerated private keys of affected seeds offline and stole funds; amounts were not stated. Fixed firmware was released for all models; affected seeds must be migrated. Funds returned: not stated | [blog.coinkite.com](https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/) |

## Fees

| Parameter | Details |
|---|---|
| Device price | List price COLDCARD Q $369, COLDCARD Mk5 $269 in the official store (as of 31 October 2026); a one-day discount was running. |
| Wallet | No account or subscription; network fees are paid through the chosen coordinator software. |

## History

| Date | Event |
|---|---|
| 2012 | Coinkite founded in Toronto, Canada. |
| 24 July 2018 | COLDCARD firmware source published; first public release in August 2018. |
| March 2022 | Mk4 firmware line released. |
| March 2024 | COLDCARD Q firmware released. |
| March 2026 | Mk5 source published. |
| 30 July 2026 | Security advisory on weakened seed generation; fixed releases published for all firmware tracks. |

## Risks and caveats

- Seeds created on affected firmware before July 2026 remain weak after a firmware update; funds must be moved to a newly generated seed.
- Air-gapped signing still requires checking destination, amount, fee and change on the device screen.
- Coinkite recommends moving long-term custody off legacy Mk2/Mk3 devices.

## About the developer

- **Developer**: Coinkite Inc., Toronto, Canada; devices designed and assembled in Canada.
- **Founded**: 2012 (Coinkite).
- **Other products**: Opendime, Tapsigner, Satscard, Seedplate, Blockclock.

## Official links

- Website: [coldcard.com](https://coldcard.com/)
- Security: [coldcard.com/security/status](https://coldcard.com/security/status)
- Docs: [coldcard.com/docs](https://coldcard.com/docs/)
- Source code: [github.com/Coldcard/firmware](https://github.com/Coldcard/firmware)
- Blog: [blog.coinkite.com](https://blog.coinkite.com/)
- Download: [store.coinkite.com/store](https://store.coinkite.com/store)

## Questions and answers

**Is COLDCARD self-custodial?**

Yes. Keys stay offline on the device, no COLDCARD account is needed, and it works with third-party Bitcoin wallet software.

**Is COLDCARD open source?**

The firmware source is public and reproducible, under MIT terms plus the Commons Clause, which restricts commercial resale of the software.

**Which coins does COLDCARD support?**

Bitcoin only.

**Was COLDCARD hacked?**

In July 2026 Coinkite disclosed a firmware bug that weakened seed generation; attackers stole funds from affected seeds offline. Fixed firmware is out, but affected seeds must be replaced.

**Who makes COLDCARD?**

Coinkite Inc. of Toronto, Canada, founded in 2012.

## Sources

- [COLDCARD — Home](https://coldcard.com/)
- [COLDCARD — About](https://coldcard.com/about)
- [COLDCARD — Security status](https://coldcard.com/security/status)
- [Coinkite blog — Coldcard Security Advisory (30 July 2026)](https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/)
- [Coinkite — Store](https://store.coinkite.com/store)
- [GitHub — Coldcard/firmware](https://github.com/Coldcard/firmware)
- [GitHub — Coldcard/firmware COPYING-CC](https://github.com/Coldcard/firmware/blob/master/COPYING-CC)

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Page updated: 2026-10-31

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Source: https://revain.org/wallets/coldcard/