Paper 2013/758

A Revocable Online-Offline Certificateless Signature Scheme without Pairing

Karthik Abinav, Saikrishna Badrinarayanan, C. Pandu Rangan, S. Sharmila Deva Selvi, S. Sree Vivek, and Vivek Krishna Pradhan

Abstract

Certificateless Public key Cryptography is a widely studied paradigm due to its advantages of not having the key-escrow problem and the lack of use of certificates. Online-Offline signature schemes are extremely relevant today because of their great practical applications. In an online-offline signature scheme all the heavy computation is done on powerful processors and stored securely in the offline phase, and the online component requires only light computation. Hence, it is widely used in several low-resource devices like mobile phones, etc. Revocation is another important problem of wide interest as it helps to keep a check on misbehaving users. Currently, there are very few revocable certificateless signature schemes in the literature. We have addressed some of the limitations of the previously existing schemes and designed a new model for the same that involves periodic time generated keys. We present a revocable online-offline certificateless signature scheme without pairing. Pairing, though a very useful mathematical function, comes at the cost of heavy computation. Our scheme is proved secure in the random oracle model using a tight security reduction to the computational Diffie-Hellman problem.