This counter is reset every time you login correctly.)Įven if there was some critical security bug in the dual secure element that completely exposed the secrets it holds, your bitcoin would still be safe, because we encrypt the contents of the dual secure element with a one-time pad known only to the main micro. Get 13 tries before the ATECC608B bricks itself. The second Secure Element, DS28C36B), the attacker would still only Secrets of the main micro fully-known (and all the secrets held in In fact,Įven with the secure element removed from the system, and all the This remains true even if they removed the chip from the board orįully-replaced the firmware in the main microprocessor. An attackerĬannot brute-force combinations or replay a previous login sequence. The attacker must know the PIN to access the secrets. Communication isĬontrolled by complex challenges and SHA-256 responses which

To store the critical master secret: the 24-word seed phrase for your BIP39 wallet. Specifically, the Coldcard (Mk4) uses Microchip's ATECC608A and Maxim's DS28C36B, Instead, Coldcard uses two Secure Elements, from different vendors, We find it quite scary that some signing devices trust the main microprocessor with their most valuable secrets.

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