International Association
for Cryptologic Research

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.