Cryptanalysis of Two Identification Schemes

Identification scheme is a cryptographic authentication protocol which allows a client to convince the corresponding server on the authenticity of his identity, without the need to share his secret with the server. In this paper, we cryptanalyze two identification schemes and show that they are not secure against impersonation under passive attack. We also propose a fix for one of the schemes to upgrade their security to secure against impersonation under passive, active and concurrent attacks.