On forward secrecy in one-round key exchange

  • Authors:
  • Colin Boyd;Juan González Nieto

  • Affiliations:
  • Information Security Institute, Queensland University of Technology, Brisbane, Australia;Information Security Institute, Queensland University of Technology, Brisbane, Australia

  • Venue:
  • IMACC'11 Proceedings of the 13th IMA international conference on Cryptography and Coding
  • Year:
  • 2011

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Abstract

Most one-round key exchange protocols provide only weak forward secrecy at best. Furthermore, one-round protocols with strong forward secrecy often break badly when faced with an adversary who can obtain ephemeral keys. We provide a characterisation of how strong forward secrecy can be achieved in one-round key exchange. Moreover, we show that protocols exist which provide strong forward secrecy and remain secure with weak forward secrecy even when the adversary is allowed to obtain ephemeral keys. We provide a compiler to achieve this for any existing secure protocol with weak forward secrecy.