This is a small, simple implementation of the various SHA2 varieties, including HMAC versions.

Advantages:

• Small (<500 lines, including header).
• Simple to integrate (single .c and .h).
• Public domain.
• Includes HMAC support.
• Simple API, for example removing version complications.
• Code clearly maps to standard.
• Only requires memcpy/memset and uint*_t from your build environment.
• No dynamic allocation.

Disadvantages:

• Probably not the very fastest implementation (but not slow, either).

Use cases:

• Simple drop-in for a project written under any license (including commercial).
• Clear code and unencumbered license means can be easily instrumented and used when debugging a new implementation, perhaps in an uncommon language or IP-restricted environment.

100% human authored.