Continuous after-the-fact leakage-resilient group password-authenticated key exchange

During the past two decades, side-channel attacks have become a familiar method of attacking cryptographic systems, which allow an attacker to learn partial information about the internal secrets such as the secret key. A scheme that is secure in the traditional model will be vulnerable in the leakage environments, thus designing a strong, meaningful, and achievable security scheme to capture the practical leakage attacks is one of the primary goals of leakage-resilient cryptography. In this work, we first formalize a continuous after-the-fact (AF) security model for leakage-resilient (LR) group password-authenticated key exchange (GPAKE) protocol, where the leakages are continuous and are allowed even after the adversary is given the challenges. Then, by combining Diffie-Hellman group key exchange protocol and Dziembowski-Faust leakageresilient storage scheme appropriately, we propose the first LR GPAKE protocol and present a formal security proof in the standard model. © 2019, International Journal of Network Security.