Fast Recursive SHA256

A fast recursive SHA-256 (SHA256) implementation in C++ intrinsics with Intel SHA Extensions or ARM Cryptography Extensions, and extra source code optimizations.

Created as a contribution to optimize the VDF (verifiable delay function) creation part by TimeLord in MMX blockchain.

The SHA256 algorithm used recursively can be a method for securing that an amount of sequential computation time has passed (VDF). Once created, easy to verify with checkpoints and parallel SHA256 processing. A valid, but niche way of using SHA256.

There is also a pipelined edition for verifying VDF.

TLDR;

I just want free fast recursive SHA256:

• Use at own responsibility (LICENSE)
• Copy rsha256_fast_x64.cxx into project (Intel)
• Copy rsha256_fast_arm.cxx into project (ARM)
• Call rsha256_fast() function

Recommended:

• Make checks/fallback if Extensions not available

Requirement

CPU: Intel/AMD x64 (w/ SHA Extensions).
CPU: ARMv8 (w/ Cryptography Extensions).
Model: Intel 11th-gen (Rocket Lake), AMD Zen, or later (a few exceptions).
Model: ARMv8, or later (Extensions are optional license, check spec sheet).

Windows: CPU-Z (Instructions) or HWiNFO64 (Features), look for SHA.
Linux: grep -o 'sha_ni' /proc/cpuinfo, empty if not available (Intel).
Linux: grep -o 'sha2' /proc/cpuinfo, empty if not available (ARM).

Usage

To use in your own project. Copy rsha256_fast_x64.cxx or rsha256_fast_arm.cxx file (only one needed). Remaining files are to illustrate optimizations done and perform benchmark. Function call:

void rsha256_fast(        //-- no return value, result to *hash
uint8_t*       hash,      //-- input/output 32bytes hash/data SHA256 value
const uint64_t num_iters) //-- number of times to SHA256 32bytes given in *hash

Benchmark

Intel 13th-gen CPU P-core at 6.0 GHz (Windows/VS2022): 42.48 MH/s

Look BENCHMARK.md for more information, and results.

Optimization

Look OPTIMIZE.md for more information, and CHANGES.md for revisions.

Donation

If you find implementation useful, donations are welcome:

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