Multi-cycle non-parallel data encryption engine

A multi-cycle, non-parallel DES encryption scheme that supports CBC, OFB, CFB, and ECB modes of operation. Three independent cipher stages are coupled together in series in order to implement a high-speed DES core. Sixteen cipher operations are required for DES encryption and decryption. Hence, the data is routed through the DES core five times. On the sixth pass, the encrypted/decrypted data is taken from the output of the first cipher stage. This output can then be used to encrypt/decrypt any subsequent input data. A different key is supplied to each of the cipher stages for each cycle.