Hardware realization of OCB mode for efficient authenticated encryption

by Al Faresi, Ahmed

Authenticated-Encryption modes of operation have recently received great atten-

tion amongst researchers. Such modes of operation provide both privacy and authentic-

ity. A proposed mode in this category is the Offset Codebook mode (OCB) by Rogaway

et al. This mode shows great substantial advantages over conventional modes. In the

past when one wanted a shared-key mechanism that provided both privacy and authen-

tication one would first encrypt separately and then use a Message Authentication Code

(MAC). The cost of such a mechanism is equal to the cost of encryption plus the cost

of producing the MAC, usually done with different keys for each operation. The OCB

mode however uses one key and provides privacy and authenticity simultaneously and

with lower costs and higher speed then conventional methods.

Since this mode is relatively new, the proposed work provides a synthesizable

hardware implementation of the OCB encryption algorithm. Furthermore an efficient

hardware realization of the Advanced Encryption Standard (AES) to be incorporated

in the OCB mode is provided. The architectural designs presented are analyzed and

synthesized in terms of performance and overall throughput. The results are evaluated

against other conventional modes in this area.