Does anybody know how to break monoalphbetic substitution cipher, if it is applied to some pseudorandom text (for example to some surrogate key filed in a database)?
Let us assume that we have only cipher text, and don't know anything about distribution of different characters appearance probabilities, so frequency analysis doesn't work. Is there some other approach?
Background: I just need to "encrypt" (not really encrypt, possibility to decrypt is not necessary) key fields in a db, keeping the length of it and avoiding collisions (don't ask why).
And I just cannot google out some encryption algorithm which will satisfy both clauses. Cryptographic hash functions are too long, common encryption algorithms can not guaranty absence of collisions, and actually also basically have a limit of length. So the only solution which I can imagine is a substitution cipher, and I want to know how weak it would be in my case.