3rdparty/p256-m/README.md

The files within the `p256-m/` subdirectory originate from the [p256-m GitHub repository](https://github.com/mpg/p256-m), which is distributed under the Apache 2.0 license. They are authored by Manuel Pégourié-Gonnard. The files `p256-m.c` and `.h` have been taken from the repository. p256-m is a minimalistic implementation of ECDH and ECDSA on NIST P-256, especially suited to constrained 32-bit environments. Mbed TLS documentation for integrating drivers uses p256-m as an example of a software accelerator, and describes how it can be integrated alongside Mbed TLS.

It should be noted that p256-m does not supply its own cryptographically secure RNG function. An implementation based on `rand()` (taken from `benchmark.c` in the p256-m repo) has been added to `p256-m.c` to support key generation. This means that while key generation will work, p256-m's key generation entry point should not be called in production builds.