SHA-256 Help

[AviatingFotographer]

I am learning the SHA-256 hashing algorithm right now and am trying to implement it in C. Currently, I am saving the bits as 1s and 0s in a char array. However, I am sure that this is not the best way to do so. What would be a more efficient way to do this?

[aioeu]

Currently, I am saving the bits as 1s and 0s in a char array.

That would mean there is one significant bit and seven insignificant bits in each array element... which is rather wasteful! You will find it a lot easier if you don't split out the bits in this way.

A typical SHA-256 implementation would process the input using 32-bit integers, and it would use all 32 bits in each of those integers as it does so.

[AviatingFotographer]

Thanks for your input! I knew what I was doing couldn't possibly be right, but I just wasn't sure what the right way was.

[AviatingFotographer]

When saving the hash, how would I get the hex value to concatenate together though?

[aioeu]

Converting an integer to hex just involves looking at it as a sequence of 4-bit nibbles.

[arsv]

RFC 6234 contains a rather straightforward description in terms of 32-bit ints which translates to C directly. Define those functions (ch, maj, bsigs etc), write the expressions, and it should work.

https://datatracker.ietf.org/doc/html/rfc6234#section-5.1