micro-ecc

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

The static version of micro-ecc (ie, where the curve was selected at compile-time) can be found in the “static” branch.

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.

Usage Notes

Point Representation

Compressed points are represented in the standard format as defined in http://www.secg.org/sec1-v2.pdf; uncompressed points are represented in standard format, but without the 0x04 prefix. All functions except uECC_decompress() only accept uncompressed points; use uECC_compress() and uECC_decompress() to convert between compressed and uncompressed point representations.

Private keys are represented in the standard format.

Using the Code

I recommend just copying (or symlink) the uECC files into your project. Then just #include "uECC.h" to use the micro-ecc functions.

For use with Arduino, you can use the Library Manager to download micro-ecc (Sketch=>Include Library=>Manage Libraries). You can then use uECC just like any other Arduino library (uECC should show up in the Sketch=>Import Library submenu).

See uECC.h for documentation for each function.

Compilation Notes

Should compile with any C/C++ compiler that supports stdint.h (this includes Visual Studio 2013).
If you want to change the defaults for any of the uECC compile-time options (such as uECC_OPTIMIZATION_LEVEL), you must change them in your Makefile or similar so that uECC.c is compiled with the desired values (ie, compile uECC.c with -DuECC_OPTIMIZATION_LEVEL=3 or whatever).
When compiling for a Thumb-1 platform, you must use the -fomit-frame-pointer GCC option (this is enabled by default when compiling with -O1 or higher).
When compiling for an ARM/Thumb-2 platform with uECC_OPTIMIZATION_LEVEL >= 3, you must use the -fomit-frame-pointer GCC option (this is enabled by default when compiling with -O1 or higher).
When compiling for AVR, you must have optimizations enabled (compile with -O1 or higher).
When building for Windows, you will need to link in the advapi32.lib system library.