Duplexing the sponge: single-pass authenticated encryption and other applications

  • Authors:
  • Guido Bertoni;Joan Daemen;Michaël Peeters;Gilles Van Assche

  • Affiliations:
  • STMicroelectronics, Belgium;STMicroelectronics, Belgium;NXP Semiconductors, Belgium;STMicroelectronics, Belgium

  • Venue:
  • SAC'11 Proceedings of the 18th international conference on Selected Areas in Cryptography
  • Year:
  • 2011

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Abstract

This paper proposes a novel construction, called duplex, closely related to the sponge construction, that accepts message blocks to be hashed and---at no extra cost---provides digests on the input blocks received so far. It can be proven equivalent to a cascade of sponge functions and hence inherits its security against single-stage generic attacks. The main application proposed here is an authenticated encryption mode based on the duplex construction. This mode is efficient, namely, enciphering and authenticating together require only a single call to the underlying permutation per block, and is readily usable in, e.g., key wrapping. Furthermore, it is the first mode of this kind to be directly based on a permutation instead of a block cipher and to natively support intermediate tags. The duplex construction can be used to efficiently realize other modes, such as a reseedable pseudo-random bit sequence generators and a sponge variant that overwrites part of the state with the input block rather than to XOR it in.