Interactive diffie-hellman assumptions with applications to password-based authentication
FC'05 Proceedings of the 9th international conference on Financial Cryptography and Data Security
Security Analysis of the PACE Key-Agreement Protocol
ISC '09 Proceedings of the 12th International Conference on Information Security
A New Protocol for the Nearby Friend Problem
Cryptography and Coding '09 Proceedings of the 12th IMA International Conference on Cryptography and Coding
Inscrypt'10 Proceedings of the 6th international conference on Information security and cryptology
Restricted identification scheme and diffie-hellman linking problem
INTRUST'11 Proceedings of the Third international conference on Trusted Systems
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This note discusses two Decisional Diffie-Hellman assumption variants introduced by Abdalla and Pointcheval at Financial Cryptography' 05. Those authors introduce two new problems and associated assumptions called the Chosen-Basis Decisional Diffie-Hellman assumption #1 (CDDH1), and the Chosen-Basis Decisional Diffie-Hellman assumption #2 (CDDH2), and suggest that these assumptions warrant further analysis. The problems are each defined in terms of a formal experiment, and advantage function, and the assumption is that an adversary should have negligible advantage. However, in this note, we exhibit a simple adversary for each problem, such that the advantage is significant. These new assumptions were motivated by the requirements of a proof of security for a three-party password authentication scheme described by the same authors. We conclude that the level of security assurance provided by this scheme is an open question.