Security analysis of a practical “on the fly” authentication and signature generation

Abstract

In response to the current need for fast, secure and cheap public-key cryptography, we study an interactive zero-knowledge identification scheme and a derived signature scheme that combine provable security based on the general problem of computing discrete logarithms modulo any number, short identity-based keys, very short transmission and minimal on-line computation. This leads to both efficient and secure applications well suited to the implementation on low cost smart cards. We develop complete proofs of completeness, soundness and statistical zero-knowledge property of the identification scheme. The security analysis of the signature scheme leads to present a novel number theoretical lemma of independent interest and an original use of the “forking lemma” technique. From a practical point of view, the possible choice of parameters is discussed and we submit performances of an actual implementation on a cheap smart card. As an example, a complete and secure authentication can be performed in less than 20 ms with low cost equipment.