International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: TMAC: Two-Key CBC MAC

Kaoru Kurosawa
Tetsu Iwata
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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.
  title={TMAC: Two-Key CBC MAC},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography / AES, secret-key cryptography, message authentication codes},
  note={NIST submission 11879 received 10 Jul 2002, last revised 11 Jul 2002},
  author={Kaoru Kurosawa and Tetsu Iwata},