Efficient, Pairing-Free, Authenticated Identity Based Key Agreement in a Single Round

Abstract

Ever since Shamir introduced identity based cryptography in 1984, there has been a tremendous interest in designing efficient key agreement protocols in this paradigm. Since pairing is a costly operation and the composite order groups must be very large to ensure security, we focus on pairing free protocols in prime order groups. We propose a new protocol that is pairing free, working in prime order group and having tight reduction to Strong Diffie Hellman (SDH) problem under the CK model. Thus, the first major advantage is that smaller key sizes are sufficient to achieve comparable security. Our scheme has several other advantages. The major one being the capability to handle active adversaries. All the previous protocols can offer security only under passive adversaries. Our protocol recognizes the corruption by an active adversary and aborts the process. Achieving this in single round is significantly challenging. Ours is the first scheme achieving this property. In addition to this significant property, our scheme satisfies other security properties that are not covered by CK model such as forward secrecy, resistance to reflection, key compromise impersonation attacks and ephemeral key compromise impersonation attacks.