Abstract

Identity Based Encryption (IBE) has been constructed from bilinear pairings, lattices and quadratic residuosity. The latter is an attractive basis for an IBE owing to the fact that it is a well-understood hard problem from number theory. Cocks constructed the first such scheme, and subsequent improvements have been made to achieve anonymity and improve space efficiency. However, the anonymous variants of Cocks’ scheme thus far are all less efficient than the original. In this paper, we present a new universally-anonymous IBE scheme based on the quadratic residuosity problem. Our scheme has better performance than the universally anonymous scheme from Ateniese and Gasti (CT-RSA 2009) at the expense of more ciphertext expansion.