Add sha224

[BRULE Herman Jacques Roger]

Hi, can you add sha224?

[Stephan Brumme]

What exactly do you mean ?
a) SHA-224 (based on SHA2) or
b) SHA3-224

[BRULE Herman Jacques Roger]

SHA-224 (based on SHA2)

[Stephan Brumme]

I added a #define SHA2_224_SEED_VECTOR in file sha256.cpp which is disabled by default.

If you enable it then you "almost" get SHA2/224: you still need to throw away the last 32 bits of getHash().

Example: an empty string will give you a hash value
d14a028c2a3a2bc9476102bb288234c415a2b01f828ea62ac5b3e42fbdd387cb
but the actual SHA2/224 of that empty string is
d14a028c2a3a2bc9476102bb288234c415a2b01f828ea62ac5b3e42f
so you need to remove the last 32/4 = 8 hexadecimal characters bdd387cb
(basically getHash().resize(224/4) will do the trick).

Since the whole class is called SHA256 I'm reluctant to fully integrate SHA2-224 and hope you can work with that limitation.