Portable C code

The parts of ocrypto that are not speed-critical are implemented in portable C89 code.

Assembly-language optimizations

For the following instruction set architectures, ocrypto provides optimized assembly-language implementations of the performance-critical functions, for 32-bit processor cores:

Instruction set architectures Processor cores (examples)
ARMv6 ARM1176 (e.g., as on Raspberry Pi Zero)
ARMv6-M Cortex-M0/M0+
ARMv7-M Cortex-M3
ARMv7E-M Cortex-M4/M7 (two variants: with/without FPU)
ARMv8-M Baseline Cortex-M23
ARMv8-M Mainline Cortex-M33/M35P (four variants: with/without DSP, with/without FPU)
ARMv7-A Cortex-A7
ARMv8-A (T32) Cortex-A53/72 (e.g., as on Raspberry Pi 3/4 Model B using a 32-bit OS)
MIPS32R2-LE MIPS microAptiv UP without DSP, little endian
MIPS32R2-LE-DSP MIPS microAptiv UP with DSP, little endian
MIPS32R2-BE MIPS microAptiv UP without DSP, big endian
MIPS32R2-BE-DSP MIPS microAptiv UP with DSP, big endian

Supported compilers are GCC, and for Cortex-M additionally Keil and IAR.

If no assembly-language optimizations are used, make sure that your C compiler only emits constant-time add and multiply operations.