SHAmwow

Sometimes you just want to understand how an algorithm works, so you implement it yourself.

The sha2 function in shamwow.rb implements the SHA-256 hashing function in Ruby. shamwow_test.rb contains a few sanity tests for the right-rotate function and for SHA2 itself, testing against the output of the Digest::SHA2.hexdigest method in the Ruby standard library.

It should go without saying that this was just for fun, and you should never, ever roll-your-own cryptography primatives for any reasonable purpose!

This was fun.

Sources

• the actual spec: http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf
• wikipedia's pseudocode breakdown: https://en.wikipedia.org/wiki/SHA-2#Pseudocode
• a JS implementation that helped as I was debugging some boneheaded mistakes: http://www.movable-type.co.uk/scripts/sha256.html

Obligatory