For a company working with a legacy system I’m trying to reverse engineer an old encryption method they use. The sourcecode for this software is missing or so I’ve been told. (or maybe they don’t want me to see the complete workings of the system).
Anyway the system uses a UNIQUE identifier and some other information to create a key.
This key is used to encrypt some data.
I need to reverse engineer this algorithm. (I may be in waaay over my head here but I’m gonna try).
I am in posession of the information used to create the key, and the encrypted AND unencrypted data.
So my best bet was to use a “Know Plaintext attack”. But I’m looking for some tips or sites with more information on how to proceed.
I know this might be an impossible task, but hey it’s nice to try, right?
Your task is not impossible – just improbable.
If you’re in possession of the key and the plaintext then I’d suggest running them through as many standard algorithms as you can. It’s very likely that whoever implemented the system used a common implementation of a standard algorithm.
You might fall short, since any sufficiently modern cipher should not be susceptible to a known plaintext attack: http://en.wikipedia.org/wiki/Known-plaintext_attack