How Weak Was the Coldcard Bug, Really? A New Video Puts It in Atoms and Galaxies
Understanding why the Coldcard entropy bug was so damaging requires understanding what protects a Bitcoin wallet in the first place: sheer numerical scale. Simply Bitcoin aired a video from the Bitcoin Policy Institute this week that tries to make that scale tangible, translating the size of a Bitcoin seed phrase's search space into physical objects a viewer can actually picture.
THE MATH BEHIND A SEED PHRASE
A Bitcoin wallet's seed phrase is only as safe as the number of possibilities an attacker would have to search through to guess it. A properly generated wallet is designed to produce recovery seeds with roughly 128 bits of entropy. The video's premise is to let a single atom stand in for a single possible seed phrase, then scale up through real objects, a protein, a virus, a grain of sand, a planet, an entire galaxy, to show how enormous that number actually is when seeds are generated correctly.
FROM A GRAIN OF SAND TO TWO BILLION GALAXIES
Under that framing, a correctly generated 256-bit space would require roughly two billion Milky Way-sized galaxies' worth of atoms to represent every possible seed, according to the video's model. The affected Coldcard firmware shrank that search space down to something a modern computer could brute force in a matter of hours, the visual equivalent of finding one marked atom inside a single virus rather than hidden across billions of galaxies.
WHAT ACTUALLY WENT WRONG ON COLDCARD
The flaw affected firmware versions that caused wallets to generate recovery seeds with approximately 40 bits of entropy instead of the intended 128 bits. Coinkite has said the effective entropy landed even lower on older Mk3 units and somewhat higher, though still far short of the standard, on Mk4, Mk5 and Q devices. The gap between those numbers and the 128-bit standard is the entire story: a seed that looks identical to a properly generated one on a device screen can, in practice, be searchable in hours instead of being effectively unguessable.
THE AI QUESTION HANGING OVER THE BUG
Part of what has unsettled the Bitcoin community is not just the bug itself but how it may have been found. Coinkite has stated in its own writeup that because Coldcard's source code is open and public, it must assume an attacker used advanced AI models to review older firmware versions and identify the entropy flaw, and the company acknowledged that its own earlier AI-assisted code reviews had missed the bug. Simply Bitcoin's hosts framed this as a preview of the kind of threat a future quantum computer could pose to public keys more broadly, a comparison raised on the show rather than a claim about the current attack, which the hosts were careful to note has nothing to do with quantum computing.
WHY THE VISUAL MATTERS
The point of the exercise is not to relitigate who is to blame for the bug. It is to make an abstract cryptographic concept, entropy, concrete enough that a non-technical Bitcoin holder can understand exactly why a working hardware wallet with a working screen and a normal-looking seed phrase could still leave funds exposed for years without anyone noticing. That is also the argument for not relying on any single device to protect a life's savings in the first place.
This story comes from the Simply Bitcoin Live show. Watch the full episode.
