TL;DR
The OPTIGA Trust M V3 is a secure element from Infineon, certified CC EAL6+. Trezor and BitBox use it as a guard: it checks your PIN and releases a secret that unlocks the keys, while the bitcoin code stays on an open-source microcontroller.
Why this chip
Most secure elements come with non-disclosure agreements that stop wallet makers from publishing how they use them. Trezor says it picked the OPTIGA Trust M because its documentation is available without an NDA, which fits open-source firmware. BitBox uses the same chip in the BitBox02 Nova, for the same reason.
What it does in a Trezor Safe 5
- Checks your PIN, without storing the PIN itself.
- Holds a secret that, together with your PIN, decrypts the keys stored on the main chip. It only releases that secret after a correct PIN.
- Adds its own randomness when a new seed is created.
- Holds a certificate that proves the device is genuine, used by Trezor Suite’s authenticity check.
What it doesn’t do
Sign transactions. That happens on the main microcontroller, running Trezor’s open-source firmware. The secure element provides physical protection, and all the code that handles your bitcoin can be checked by anyone. See what is a secure element.
Certification
Common Criteria EAL6+, with protection against fault injection and side-channel attacks. What that level means is explained in CC EAL6+ explained.
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