Coldcard strengthens seed generation with firmware update

Coinkite released a new security upgrade to strengthen seed phrase generation by requiring user-supplied entropy mixed with improved device randomness.

Coinkite announced firmware 5.6.1 for Coldcard Mk4 and Mk5 devices and 1.5.1Q for the Coldcard Q in a Thursday blog post.

The release requires newly generated seeds to include user-supplied entropy through at least 65 keypresses with unpredictable timing, 50 rolls of a six-sided die or 128 coin flips. That input is combined with randomness from multiple device sources, including its secure elements and hardware random-number generator (RNG).

The combined randomness is used to create the wallet’s seed phrase and is intended to keep its private keys unpredictable even if one of the device’s entropy sources fails.

Coinkite told users to upgrade immediately, emphasizing that existing seed phrases remain vulnerable even after upgrading and must be replaced with new seeds before migrating funds. 

Confirmed losses from the Coldcard exploit reached 1,778 Bitcoin (BTC), worth about $112 million, according to an Aug. 14 report by Galaxy Research. This makes the Coldcard hack the third-largest cryptocurrency exploit of 2026, according to data aggregated by DefiLlama.