Coldcard review
Last reviewed 2026-08-25
Security warning
Do not generate a new seed on a Coldcard until you have installed the fixed firmware for your model, and if your current seed was created on a Coldcard before that firmware, move your coins to a new one. Coinkite's own advisory is unusually clear about this, and the flaw behind it ran for more than five years.
What happened: in March 2021 Coinkite moved Coldcard's elliptic-curve code onto Bitcoin Core's libsecp256k1 through an embedded library called libNgU. The cryptography was sound; the build was not. A link-time error meant the call that was supposed to reach the hardware random number generator resolved instead to MicroPython's general purpose software generator, so seeds were drawn from far less randomness than the design intended. Coinkite estimates the effective search space at about 40 bits on the Mk2 and Mk3 and about 72 bits on the Mk4, Mk5 and Q, against a 128 bit target, and calls both figures preliminary.
Two exceptions matter, and Coinkite states both. A seed created with at least 50 fair, independent, private dice rolls is not at risk from this issue alone, because the dice supplied the entropy the device did not: Coldcard hashed every roll together with the device entropy, and 50 to 98 rolls contribute at least 128 bits on their own. And a strong, unique BIP-39 passphrase is an independent barrier that reduced seed entropy alone does not get past, though it repairs nothing, so Coinkite still tells passphrase users to migrate as soon as practical. TAPSIGNER, OPENDIME and SATSCARD run different codebases and are not affected.
On the size of the losses, Coinkite's advisory names no dollar or bitcoin total. TRM Labs published its analysis as the largest hardware wallet exploit of 2026, putting it at about $116 million; Galaxy Research put the figure at $130 million and counting. Treat those as two outside estimates rather than a settled number.
What Coldcard is, underneath all of that, has not changed: a bitcoin-only signer with two secure elements from different vendors, reproducible open source firmware, duress and brick PINs, and signing over QR, microSD, NFC or a virtual disk, all of which are off by default. Coinkite sells the Q at $289 and the Mk5 at $189, and says new units ship with corrected firmware. This record sits at caution because of the migration burden owners are carrying, not because the secure elements failed.
- Made by
- Coinkite
- Type
- Hardware device
- Price
- $189
- Runs on
- Windows, macOS, Linux
- Who holds the keys
- self-custodial, keys held behind two secure elements from different vendors, signing air-gapped by choice
- Bitcoin only
- Yes
- Screen
- Q: 3.2 inch LCD with a full keyboard. Mk5: bright OLED with a numeric keypad
- Connectivity
- USB-C, microSD, NFC, QR scanner on the Q and a virtual disk mode, every path off by default
- Released
- Coinkite has made Coldcard since 2017; the Q and the Mk5 are the current models
- Coin support
- Bitcoin only, and it doubles as an offline vault for seeds, passwords and notes belonging to other wallets
Pros and cons
What works
- Bitcoin only, which keeps every other chain's parsing code off the device
- Two secure elements from independent vendors, so one chip flaw is not enough
- Air-gapped signing over QR, microSD, NFC or virtual disk, with all data paths disabled by default
- Reproducible open source firmware that advanced users can build and verify themselves
- Duress PIN, brick PIN and login countdown for coercion scenarios
- Coinkite's advisory published the technical cause, the entropy estimates and step by step migration instructions
What to watch
- A March 2021 build error weakened seed generation for over five years, and updating the firmware does not repair an affected seed
- Migrating means generating a new seed and moving every coin, which costs an on-chain transaction and real care
- Coinkite publishes no loss total, so the scale rests on outside estimates from TRM Labs and Galaxy Research
- Steeper learning curve than a Ledger or a Trezor, with no companion app of its own
- Coinkite publishes no shipping country policy at all
Worth comparing
- BitBox02Swiss made, fully open source, sold in Multi and Bitcoin-only editions, with a Nova model that works from an iPhone.
- Blockstream JadeBitcoin-only line from $79 to $149 that ships no secure element on purpose: a locked Jade holds nothing worth extracting.
- Foundation PassportBitcoin-only hardware from a US company, now sold as the $349 Passport Prime: keys, two factor codes, security keys and encrypted storage in one device.
Frequently asked questions
Is my Coldcard affected by the seed entropy bug?
If the seed was generated on a Mk2 or Mk3 running firmware 4.0.1 through 4.1.9, or on an Mk4, Mk5 or Q before the fixed release for your track, then yes, unless you added at least 50 fair, independent, private dice rolls when you created it. Coinkite's advisory walks through the migration step by step.
Does a passphrase protect me?
A strong, unique BIP-39 passphrase is an independent barrier, and Coinkite says the reduced seed entropy alone is not enough to reach funds behind one. It does not repair the seed, and a short, patterned or reused passphrase does not count, so Coinkite still tells passphrase users to migrate as soon as practical.
Are TAPSIGNER, OPENDIME and SATSCARD affected?
No. Coinkite states that all three run different codebases and are not affected by this bug.
How much was stolen in the Coldcard hack?
Coinkite's own advisory names no total. TRM Labs put it at roughly $116 million and called it the largest hardware wallet exploit of 2026; Galaxy Research put it at $130 million and counting. Those are two outside on-chain estimates, not a confirmed figure.
Should I still buy a Coldcard?
New units ship with corrected firmware, and Coinkite tells buyers to update on receipt anyway. If you want a bitcoin-only signer with dual secure elements and open firmware, it is still that. If the episode has cost you confidence, the closest alternatives here are the BitBox02 Bitcoin-only edition, Blockstream Jade and Foundation Passport.