Authenticated Key Exchange and Key Encapsulation Without Random Oracles

This paper presents a new paradigm to realize cryptographic primitives such as authenticated key exchange and key encapsulation without random oracles under three assumptions: the decisional Diffie-Hellman (DDH) assumption, target collision resistant (TCR) hash functions and a class of pseudo-random functions (PRFs), $\pi$PRFs, PRFs with pairwise-independent random sources. We propose a (PKI-based) two-pass authenticated key exchange (AKE) protocol that is comparably as efficient as the existing most efficient protocols like MQV and that is secure without random oracles (under these assumptions). Our protocol is shown to be secure in the (currently) strongest security definition, the extended Canetti-Krawczyk (eCK) security definition introduced by LaMacchia, Lauter and Mityagin. We also show that a variant of the Kurosawa-Desmedt key encapsulation mechanism (KEM) using a $\pi$PRF is CCA-secure under the three assumptions. This scheme is secure in a stronger security notion, the chosen public-key and ciphertext attack (CPCA) security, with using a generalized TCR (GTCR) hash function in place of a TCR hash function. The proposed schemes in this paper are validity-check-free and the implication is that combining them with validity-check-free symmetric encryption (DEM) will yield validity-check-free (e.g., MAC-free) CCA-secure hybrid encryption

Review on Leakage Resilient Key Exchange Security Model

In leakage resilient cryptography, leakage resilient key exchange protocols are constructed to defend against leakage attacks. Then, the key exchange protocol is proved with leakage resilient security model to determine whether its security proof can provide the security properties it claimed or to find out any unexamined flaw during protocol building. It is an interesting work to review the meaningful security properties provided by these security models. This work review how a leakage resilient security model for a key exchange protocol has been evolved over years according to the increasing security requirement which covers a different range of attacks. The relationship on how an adversary capability in the leakage resilient security model can be related to real-world attack scenarios is studied. The analysis work for each leakage resilient security model here enables a better knowledge on how an adversary query addresses different leakage attacks setting, thereby understand the motive of design for a cryptographic primitive in the security model

Authenticated Key Exchange and Key Encapsulation without Random Oracles

This paper presents a new paradigm to realize cryptographic primitives such as authenticated key exchange and key encapsulation without random oracles under three assumptions: the decisional Diffie-Hellman (DDH) assumption, target collision resistant (TCR) hash functions and a class of pseudo-random functions (PRFs), πPRFs, PRFs with pairwise-independent random sources. We propose a (PKI-based) two-pass authenticated key exchange (AKE) protocol that is comparably as efficient as the existing most efficient protocols like MQV and that is secure without random oracles (under these assumptions). Our protocol is shown to be secure in the (currently) strongest security definition, the extended Canetti-Krawczyk (eCK) security definition introduced by LaMacchia, Lauter and Mityagin. We also show that a variant of the Kurosawa-Desmedt key encapsulation mechanism (KEM) using a πPRF is CCA-secure under the three assumptions. This scheme is secure in a stronger security notion, the chosen public-key and ciphertext attack (CPCA) security, with using a generalized TCR (GTCR) hash function in place of a TCR hash function. The proposed schemes in this paper are validity-check-free and the implication is that combining them with validity-check-free symmetric encryption (DEM) will yield validity-check-free (e.g., MAC-free) CCA-secure hybrid encryption