Cryptology ePrint Archive: Report 2002/092


Kaoru Kurosawa and Tetsu Iwata

Abstract: In this paper, we propose TMAC, Two-Key CBC Message Authentication Code. TMAC is a refinement of XCBC (which is a variant of CBC MAC) shown by Black and Rogaway. We use only $(k+n)$-bit key for TMAC while XCBC uses $(k+2n)$-bit key, where $k$ is the key length of the underlying block cipher and $n$ is its block length. The cost for reducing the size of secret keys is almost negligible; only one shift and one conditional XOR. Similarly to XCBC, our algorithm correctly and efficiently handles messages of arbitrary bit length.

Category / Keywords: secret-key cryptography / AES, secret-key cryptography, message authentication codes

Publication Info: NIST submission

Date: received 10 Jul 2002, last revised 11 Jul 2002

Contact author: iwata at cis ibaraki ac jp

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Version: 20020711:093538 (All versions of this report)

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