[difficulty: 6][protection: custom finite field cipher activity]
Contains a block cipher utilizing finite field arithmetic. You can invert it by reversing the operations and inverting certain field operations. Your serial must encrypt to some values generated from the name and Allen Ginsberg's poem "Howl" (what is an angelheaded hipster anyways!?).
Check out the code for some real calculation of multiplicative inverses in the field using the Euclidean algorithm (no bruteforcing this time!!)