Non-Interactive Key Exchange

Non-interactive key exchange (NIKE) is a fundamental but much-overlooked cryptographic primitive. It appears as a major contribution in the ground-breaking paper of Diffie and Hellman, but NIKE has remained largely unstudied since then. In this paper, we provide different security models for this primitive and explore the relationships between them. We then give constructions for secure NIKE in the Random Oracle Model based on the hardness of factoring and in the standard model based on the hardness of a variant of the decisional Bilinear Diffie Hellman Problem for asymmetric pairings. We also study the relationship between NIKE and public key encryption (PKE), showing that a secure NIKE scheme can be generically converted into an IND-CCA secure PKE scheme. This conversion also illustrates the fundamental nature of NIKE in public key cryptography

Generalization of the Selective-ID Security Model for HIBE Protocols

Abstract. We generalize the selective-ID security model for HIBE by introducing two new security models. Broadly speaking, both these models allow the adversary to commit to a set of identities and in the challenge phase choose any one of the previously committed identities. Two constructions of HIBE are presented which are secure in the two models. Further, we show that the HIBEs can be modified to obtain a multiple receiver IBE which is secure in the selective-ID model without the random oracle assumption.