CryptoSlate
Coldcard maker Coinkite released new standard firmware on Aug. 20 that forces Bitcoin hardware wallet users to add physical randomness whenever they generate a seed: at least 65 key presses at unpredictable intervals, 50 rolls of a six-sided die, or 128 physical coin flips. The mandate comes after a flaw that let attackers reconstruct private keys from a single button press on affected firmware, and Coinkite says some customers have already suffered severe losses. Installing the fixed firmware does not retroactively secure existing seeds, so affected owners must generate a fresh seed and migrate balances unless a documented dice-roll exception applies.
Why it matters
The root cause, traced independently by Block, was code that routed requests to a deterministic MicroPython fallback because a feature flag defined as zero was treated as present. That kind of bug is structural rather than a random glitch, which is why Coinkite is treating every seed generated under the affected firmware as potentially reconstructible. The mandatory human input now required for new standard seeds adds outside entropy and limits damage if device randomness fails again, but it cannot retrofit entropy onto a seed that already exists. Coinkite says law enforcement is investigating and some customers suffered severe losses, though no verified victim count or loss total has been published.
Market impact
The exposure boundary is wider than Coinkite's own advisory. Coinkite's migration guidance covers Mk2 and Mk3 firmware 4.0.1 through 4.1.9, Mk4 and Mk5 standard firmware before 5.6.0 and Edge firmware before 6.6.0X, and Q standard firmware before 1.5.0Q and Edge firmware before 6.6.0QX, while Block's technical analysis extends the Mk2 and Mk3 boundary to include 4.0.0. Owners of version 4.0.0 should not treat the vendor boundary as proof of safety. Current fixed releases are 5.6.1 for Mk4 and Mk5 and 1.5.1Q for Q devices.
Frequently asked questions
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What changed in Coldcard's new firmware?
Coinkite released firmware on Aug. 20 that requires physical randomness for every new seed: at least 65 key presses at unpredictable intervals, 50 die rolls, or 128 coin flips, alongside signing-path hardening like blocking SIGHASH_SINGLE modes by default.
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Which Coldcard firmware versions are affected?
Coinkite's migration guidance covers Mk2 and Mk3 firmware 4.0.1 through 4.1.9, Mk4 and Mk5 standard firmware before 5.6.0 and Edge firmware before 6.6.0X, and Q standard firmware before 1.5.0Q and Edge firmware before 6.6.0QX. Block's analysis extends the Mk2 and Mk3 boundary to include 4.0.0.
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Does installing the fixed firmware secure an existing seed?
No. The firmware update only hardens new seeds. Owners of affected firmware must generate a fresh seed, verify its fingerprint, send a test transaction, and migrate every balance tied to the old seed, unless the documented dice-roll exception applies.
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What is the dice-roll exception to migration?
Migration is not required when the user added at least 50 fair, independent, and private physical die rolls through the affected workflow and never recorded or exposed the sequence. Fewer rolls, or any uncertainty about those conditions, means the user should migrate.
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What was the root cause of the flaw?
Block traced the defect to code that could route requests to a deterministic MicroPython fallback because a feature flag defined as zero was treated as present, a structural bug that let attackers reconstruct private keys from a single button press.
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