International Association
for Cryptologic Research

In this paper, we present a single round two-party attribute-based authenticated key exchange protocol. 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 Attribute-based CK model which is a natural extension of the CK model for the public key setting. 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 Attribute-Based authenticated key exchange protocols can offer security only under passive adversaries. Our protocol recognizes the corruption by an active adversary and aborts the process. Ours is the first scheme achieving this property. We also show how to modify our construction to achieve anonymity of access structure of users. Our attribute-based authenticated key exchange is also the first that enjoys this property. In addition to this property, our scheme satisfies other security properties that are not covered by CK model such as forward secrecy, key compromise impersonation attacks and ephemeral key compromise impersonation attacks.