Simple integer encryption

Question

Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integ

Answer 1

I wrote an article some time ago about how to generate a 'cryptographically secure permutation' from a block cipher, which sounds like what you want. It covers using folding to reduce the size of a block cipher, and a trick for dealing with non-power-of-2 ranges.