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On Session Identifiers in Provably Secure Protocols: The Bellare-Rogaway Three-Party Key Distribution Protocol Revisited

Publication Date
  • 080600 Information Systems
  • 080000 Information And Computing Sciences
  • Session Identifiers
  • Provably Secure Protocols
  • Key Establishment Protocols


We examine the role of session identifiers (SIDs) in security proofs for key establishment protocols. After reviewing the practical importance of SIDs we use as a case study the three-party server-based key distribution (3PKD) protocol of Bellare and Rogaway, proven secure in 1995. We show incidentally that the partnership function used in the existing security proof is flawed. There seems to be no way to define a SID for the 3PKD protocol that will preserve the proof of security. A small change to the protocol allows a natural definition for a SID and we prove that the new protocol is secure using this SID to define partnering.

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