The Coldcard Disaster: Everything You Need to Know | Lloyd Fournier & Nick Farrow — Key Takeaways
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The Coldcard Disaster: Everything You Need to Know | Lloyd Fournier & Nick Farrow
What Bitcoin Did1h 23mAug 21, 2026
Watch the originalMove funds off Cold Card Mark III immediately — ~1,200 wallets holding ~2,000 BTC were compromised by entropy so weak (2²⁰ possibilities) that the attack runs on a laptop in hours.
Key takeaways
Cold Card Mark III entropy was ~2^20 bits, making brute-force feasible on a laptop
Cold Card Mark III entropy was ~2^20 bits, making brute-force feasible on a laptop
- Initial estimates were 2^40 bits; Wizard Sardine analysis revised it to millions of possibilities, empirically verified.
- Attacker swept ~1,000 BTC from 1,200+ wallets; researcher replicated the full attack overnight using Claude as coding assistant.
Yasmarang RNG is a toy 32-bit PRNG — cryptographically unsuitable, yet was Cold Card's entropy source
Yasmarang RNG is a toy 32-bit PRNG — cryptographically unsuitable, yet was Cold Card's entropy source
- Yasmarang originated in MicroPython (hobbyist toolkit), has tiny state, and is not a cryptographic CSPRNG.
- A secure CSPRNG needs ~256-bit secret key state; Yasmarang's state is so small it cannot absorb sufficient entropy.
Dark Skippy: a malicious device leaks your full seed phrase in just 2 signatures via nonce manipulation
Dark Skippy: a malicious device leaks your full seed phrase in just 2 signatures via nonce manipulation
- Previous literature assumed ~50 transactions needed; Lloyd and Robin Linus reduced it to one transaction (two signatures).
- Applies to any device that chooses its own signing nonce without anti-exfil protocol (Jade, BitBox, Frostnap implement anti-exfil).
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In this video
- 1mIntroduction
- 1mThe Coldcard Disaster
- 3mHow AI Found the Bug Humans Missed
- 7mColdcard’s Fatal Randomness Failure
- 12m1,200 Wallets, Nearly 2,000 Bitcoin
- 18mMapping the Attackers On-Chain
- 19mReproducing the Attack With AI
- 32mHardware Wallets Are Trusted Third Parties
- 36mHow Frostsnap Removes Device Trust
- 41mIs Every Hardware Wallet at Risk?
- 48mOpen Source Security in the Age of AI
- 56mThe Human Cost of the Coldcard Hack
- 1h 4mHow Frostsnap Works
- 1h 11mProtecting Bitcoin From Physical Attack
- 1h 18mFrostsnap
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