Exetools - micro-ecc

A small and fast ECDH and ECDSA implementation for 8-bit, 32-bit, and 64-bit processors.

Features:

Resistant to known side-channel attacks.
Written in C, with optional GCC inline assembly for AVR, ARM and Thumb platforms.
Supports 8, 32, and 64-bit architectures.
Small code size.
No dynamic memory allocation.
Support for 5 standard curves: secp160r1, secp192r1, secp224r1, secp256r1, and secp256k1.
BSD 2-clause license.

src:

Code:

https://github.com/kmackay/micro-ecc