NCPA: A Scheduling Algorithm for Multi-cipher and Multi-mode Reconfigurable Cryptosystem

Multi-cipher and multi-mode reconfigurable cryptosystems are widely used for hardware acceleration in modern security protocols, such as SSL and IPsec, but there has been hardly any work which can process multiple cipher algorithms with varied block lengths, key lengths and operation modes at a session of communication owing to the lack of suitable scheduling algorithms for the crypto-coprocessors and reverse schemes for the ciphertext. This paper proposes a NOP-cycle-padding algorithm (NCPA) which enables crypto-coprocessors reconfigured with diverse encrypting bursts to be pipeline scheduled. With NCPA, the output ciphertext is reversible and can be orderly sent out without any added cost in hardware or software. Moreover, the throughput can be upgraded to the maximum with an optimized number of crypto-coprocessors derived from NCPA.