[om42]

Seems like they're not using the CryptoCell to drive crypto ops and have instead written the cypto algos in software in Rust... from the README (https://github.com/google/OpenSK):

We're currently still in the process on making the ARM® CryptoCell-310 embedded in the Nordic nRF52840 chip work to get hardware-accelerated cryptography. In the meantime we implemented the required cryptography algorithms (ECDSA, ECC secp256r1, HMAC-SHA256 and AES256) in Rust as a placeholder. Those implementations are research-quality code and haven't been reviewed. They don't provide constant-time guarantees and are not designed to be resistant against side-channel attacks.