Security of Truncated MACs

  • Authors:

  • Peng Wang;Dengguo Feng;Changlu Lin;Wenling Wu

  • Affiliations:

  • State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, China 100049;State Key Laboratory of Information Security, Institution of Software of Chinese Academy of Sciences, Beijing, China 100080;State Key Laboratory of Information Security, Graduate University of Chinese Academy of Sciences, Beijing, China 100049 and Key Laboratory of Network Security and Cryptology, Fujian Normal Univers ...;State Key Laboratory of Information Security, Institution of Software of Chinese Academy of Sciences, Beijing, China 100080

  • Venue:
  • Information Security and Cryptology
  • Year:
  • 2009

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Abstract

In all of the MAC standard documents, the tag truncation is defined. Even if a MAC can be proved to be secure in the sense of unforgeability, the truncated MAC may suffer from sudden loss of security. We propose a new notion of robust unforgeability to address this problem, which is strictly stronger than the notion of unforgeability. We also give some generic methods to turn the unforgeable MAC into robustly unforgeable one. Furthermore we propose a notion of variationally XOR universal hash function, which is strictly weaker than the previously proposed notion of variationally universal hash function by Krovetz and Rogaway, to strengthen the security of Wegman-Carter MACs to be robustly unforgeable.