I am building a Rust application to run on my dev board which has a Cortex M4. And I want to generate a certificate and validate a signature with it. I looked it up on the web and found Rust based like Ring and rustls, but Ring failed to compile when I set my target to thumbv7em-none-eabi. Then I tried to build my application with openssl crate but it failed cargo check with error[E0463]: can't find crate for std.
Has anyone had any experience with Rust crypto library for Cortex M processor? I am not sure what has been supported on this particular processor.
sodiumoxide would theoretically be really nice for interoperability with other libsodium things but, i have yet to solve the compiling-on-arm problems in libsodium-sys sodiumoxide#363. If you just need elliptic curve things you might also be interested in dalek-cryptography/ed25519-dalek