C implementation of SHA256

Implementation of SHA256 (Secure Hash Algorithm 256 bit) in C. Algorithm is based on Merkle–Damgård construction and was first published under NIST FIPS PUB 180-2.

Test vectors: NIST CAVP Testing (https://csrc.nist.gov/projects/cryptographic-algorithm-validation-program/secure-hashing#shavs)

Instructions for buiding and running the code

Compile

    make
    make SHA256
    make MAIN

Run

    ./sha256
    ./main

Sample Output:

    passed!