In this work we: (1) Show the inadequacy of both the Halevi-Krawczyk formalization and protocol in the case where there is more than a single user: using a simple and realistic attack, we prove failure of the HK solution in the two-user case. (2) Propose a new definition of security for the multi-user case, expressed in terms of transcripts of the entire system, rather than individual protocol executions. (3) Suggest several ways of achieving this security against both static and dynamic adversaries.
In a recent revision of their paper, Halevi and Krawczyk attempted to handle the multi-user case. We expose a weakness in their approach.
Category / Keywords: Password Authentication, Chosen Ciphertext Attacks, Non-Malleability Publication Info: Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive. Date: received September 16, 1999. To appear in the 6th ACM Conference on Computer and Communication Security, 1999. Contact author: mkboyarsky at yahoo com Available formats: Postscript (PS) | Compressed Postscript (PS.GZ) | BibTeX Citation Discussion forum: Show discussion | Start new discussion