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.
Known issues
- EUCLEAK (2024). Researchers at NinjaLab found a side-channel flaw in Infineon’s cryptographic library that also affects the OPTIGA Trust M. With the device in hand, lab equipment and expert skills, an attacker could extract the chip’s own signing key, which in theory weakens the authenticity check. Your seed isn’t at risk: that cryptography isn’t used to create or protect it (NinjaLab’s write-up).
- BitBox02 Nova chip configuration (2025). A Trezor researcher reported two issues in how the Nova’s firmware configured the chip. BitBox fixed them in its 01.2026 firmware update. They needed physical access and only mattered if the same device password was used on several devices; the original BitBox02 isn’t affected (BitBox’s announcement).
Reviews: Trezor Safe 5 · BitBox02 vs BitBox02 Nova