Circuits, methods, and apparatus for encrypting and decrypting data using a field programmable gate array. The underlying encryption algorithm is tailored for implementation using programmable logic elements such as lookup tables or macrocells. A specific embodiment of the present invention provides a method of encryption that is optimized for implementation using a reduced number of lookup tables. The method makes efficient use of a long key, 512 bits in a specific embodiment, and incorporates substitution or S-boxes, input whitening, permutation, and a variable number of rounds.