Who must move their coins

tftc-who-must-move

https://www.tftc.io/coldcard-rng-failed-move-your-coins

Organisation

TFTC

Evidence role

Secondary analysis

Published

2026-07-31

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Unreviewed

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Copies held

2

Every check is recorded, including checks that found no text change. A detected edit is therefore bounded between two checks. The publisher's exact save time is not observable from this record. Last checked 15 Aug 2026, 12:53 UTC.

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   Bitcoin Brief
   COLDCARD's RNG Failed. Move Your Coins.
   An urgent warning for anyone whose seed was generated on affected COLDCARD firmware. Updating the device will not repair the seed. Generate a new one and migrate carefully.
   Marty Bent
   ·July 31, 2026·8 min read
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   Bitcoin BriefEmergency Edition
   TFTC · Truth for the Commoner
   Bitcoin Brief
   Sup, freaks.
   We are sending a single-story emergency edition of the Bitcoin Brief because time matters.
   URGENT WARNING
   COLDCARD's RNG Failed. Move Your Coins.
   I have been a vocal COLDCARD advocate for years. I have trusted the product, recommended it to people I care about, and used it as an example of serious bitcoin self-custody. What came to light overnight is an absolute disaster.
   Coinkite has now confirmed that affected COLDCARD firmware used the wrong random-number generator while creating wallet seeds. Instead of drawing the intended randomness from the device's hardware, seed generation reached a deterministic MicroPython software fallback. Block's Bitcoin Engineering and Security team independently found the same failure in the source code.
   That means some wallets that looked like normal cold storage were protected by keys drawn from a search space far smaller than users had every reason to expect.
   The most acute danger is on Mk2 and Mk3 devices running version 4 firmware. Coinkite's advisory warns about Mk3 seeds generated on firmware 4.0.1 or later and currently estimates an effective search space of roughly 40 bits under its attack assumptions. Block traces the vulnerable path to version 4.0.0. Do not gamble on that one-version discrepancy. If a Mk2 or Mk3 running version 4 firmware generated your seed, treat the seed as compromised and migrate.
   The problem extends beyond the Mk3. Coinkite now says seeds generated on Mk4 and Mk5 before firmware 5.6.0, and on Q before 1.5.0Q, are also affected. Coinkite currently estimates roughly 72 bits of entropy for those later devices instead of the intended 128 bits. The later models are less exposed than the Mk3, but Coinkite still calls the weakness serious and tells users to generate a new seed after installing the fixed firmware.
   A firmware update cannot repair a seed that already exists. The weakness is baked into the private keys derived from that seed. Updating the device and continuing to use the same words leaves the problem in place.
   This disclosure arrived after a coordinated on-chain sweep moved 594.47722484 BTC into one collector address across 500 transactions and four consecutive blocks. We independently reproduced that chain event. Several reported victims said they used COLDCARD single-sig wallets, but the blockchain cannot identify the hardware that generated a key. It would be irresponsible to claim that every coin in the sweep came from this bug or that 500 transactions equal 500 victims. The firmware failure is confirmed. The exact share of the theft tied to it is still being investigated.
   That is why the priority now is action, not tribal warfare between hardware-wallet brands.
   Who should move now
   Assume the seed is at risk and prepare a migration if any of these describe you:
   A Mk2 or Mk3 running version 4 firmware generated your seed.
   A Mk4 or Mk5 generated your seed before firmware 5.6.0.
   A Q generated your seed before firmware 1.5.0Q.
   Affected firmware generated your seed, regardless of whether you also used dice rolls or a passphrase.
   You cannot remember the model, firmware, or entropy method used when the seed was created.
   The affected cohort is defined by the firmware that generated the secret, not the firmware installed today. Updating the device or restoring the same seed onto newer hardware does not strengthen the keys. You still have to create a new seed and move the coins.
   What dice and a passphrase change
   Coinkite says the dice input was hashed together with the device-generated seed. Fair, independent, private dice rolls can add real entropy, and a strong, unique BIP39 passphrase can add another independent barrier. But neither should be treated as permission to keep using a seed created by affected firmware.
   If you cannot say with complete confidence that you used at least 100 fair, independent, private dice rolls when the original seed was created, assume the keys remain vulnerable. Even if you did use at least 100 rolls or a genuinely strong passphrase, the safe response is still to replace the seed and move the coins. A device PIN is not a BIP39 passphrase.

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