One-Round Exposure-Resilient Identity-Based Authenticated Key Agreement with Multiple Private Key Generators

Abstract

This paper considers identity-based authenticated key agreement (IBAKA) with multiple private key generators (PKGs). In conventional IBAKA scenarios, a single PKG manages all parties in a system, whereas in a multiple PKG setting, several PKGs exist in a system, and each party is given a private key by a PKG who manages the party. IBAKA is expected to maintain security against exposing private information such as static or ephemeral private keys even in a multiple PKG setting. We define a security model for IBAKA with multiple PKGs to achieve this exposure-resilience property. Based on a security notion, we propose a one-round secure protocol under the gap bilinear Diffie–Hellman assumption in the random oracle model. The protocol utilize the NAXOS approach to embed the gap bilinear Diffie–Hellman instance even when both ephemeral private keys are exposed.