The Deterministic Fallacy: How a Zero Bit Broke Coldcard's Trust
0xBen
The most dangerous bugs are not the ones hidden in complex algorithms. They are the ones that exist in plain sight, disguised as a boolean. A single feature flag, defined as zero, was interpreted as present by the MicroPython runtime. That is the root cause. A Zero. Not a hardware failure, not an advanced side-channel attack, but a logic error in the deterministic path of a device whose entire value proposition is security. Coldcard, the bitcoin hardware wallet for the paranoid, has been compromised at the seed generation layer. The code executed a fallback routine for its random number generator, a deterministic one, and the device never noticed. The hardware wallet is a safe, but the combination lock was set to '1234' by a software bug. Code is law, but bugs are reality.