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Security and Communication Networks

Deniable Key Establishment Resistance against eKCI Attacks

Łukasz Krzywiecki, Tomasz Wlisłocki

Published Jan 1, 2017• 4 citations
Publisher

Abstract

In extended Key Compromise Impersonation (eKCI) attack against authenticated key establishment (AKE) protocols the adversary impersonates one party, having the long term key and the ephemeral key of the other peer party. Such an attack can be mounted against variety of AKE protocols, including 3-pass HMQV. An intuitive countermeasure, based on BLS (Boneh–Lynn–Shacham) signatures, for strengthening HMQV was proposed in literature. The original HMQV protocol fulfills the deniability property: a party can deny its participation in the protocol execution, as the peer party can create a fake protocol transcript indistinguishable from the real one. Unfortunately, the modified BLS based version of HMQV is not deniable. In this paper we propose a method for converting HMQV (and similar AKE protocols) into a protocol resistant to eKCI attacks but without losing the original deniability property. For that purpose, instead of the undeniable BLS, we use a modification of Schnorr authentication protocol, which is deniable and immune to ephemeral key leakages.

DOI
10.1155/2017/7810352

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In extended Key Compromise Impersonation (eKCI) attack against authenticated key establishment (AKE) protocols the adversary impersonates one party, having the long term key and the ephemeral key of the other peer party. Such an attack can be mounted against variety of AKE protocols, including 3-pass HMQV. An intuitive countermeasure, based on BLS (Boneh–Lynn–Shacham) signatures, for strengthening HMQV was proposed in literature. The original HMQV protocol fulfills the deniability property: a party can deny its participation in the protocol execution, as the peer party can create a fake protocol transcript indistinguishable from the real one. Unfortunately, the modified BLS based version of HMQV is not deniable. In this paper we propose a method for converting HMQV (and similar AKE protocols) into a protocol resistant to eKCI attacks but without losing the original deniability property. For that purpose, instead of the undeniable BLS, we use a modification of Schnorr authentication protocol, which is deniable and immune to ephemeral key leakages.
Abstract: Key establishment protocols are among the most important security mechanisms via which two or more parties can generate a common session key to in order to encrypt their communications over an otherwise insecure network. This paper is concerned with the vulnerability of one-pass two-party key establishment protocols to key-compromise impersonation (K-CI) attacks. The latter may occur once an adversary has obtained the long-term private key of an honest party, and represents a serious — but often underestimated — threat. This is because an entity may not be aware that her computer has been compromised and her private key is exposed, and because a successful impersonation attack may result in far greater harm than the reading of past and future conversations. Our aim is to describe two main classes of K-CI attacks that can be mounted against all of the best-known one-pass protocols, including MQV and HMQV. We show that one of the attacks described can be somewhat avoided (though not completely eliminated) through the combined use of digital signatures and time-stamps; however, there still remains a class of K-CI threats for which there is no obvious solution. 1
The extended Canetti-Krawczyk(eCK) model proposed by LaMacchia et al.is currently regarded as the strongest security model for authenticated key exchange(AKE) protocols.In the eCK model,the adversary can make queries on the test session,and reveal both ephemeral private keys,both long-term keys,or one of each from the two different parties.In this paper,we analyze two AKE protocols designed in the eCK model based on the definition of eCK model.We propose ephemeral keys compromised attacks and long-term keys compromised attacks on one of them,and also propose ephemeral keys compromised attacks on the other one.The results of analysis show that both of them are insecure in the eCK model.
Abstract This paper investigates the security model for authenticated key exchange protocols. We further enhance the enhanced Canetti‐Krawczyk (eCK) model by introducing a notion called strong key compromise impersonation (SKCI) resilience which is first identified in this paper. SKCI resilience guarantees that the adversary cannot masquerade as another party B to communicate with party A even if the static private key and the ephemeral private key of party A are compromised. We point out that the three‐pass authenticated key exchange protocol generically transformed from the two‐pass one secure in the eCK model cannot resist the SKCI attack. Finally, we introduce a new authenticated key exchange protocol SIG‐DH+ and prove that it satisfies our new definition. Copyright © 2010 John Wiley & Sons, Ltd.
In 2003, Boyd et al. have proposed two deniable authenticated key establishment protocols for Internet key exchange (IKE). However, both schemes have been broken by Chou et al. in 2005 due to their susceptibility to key-compromise impersonation (KCI) attack. In this paper, we put forward the improved variants of both Boyd et al.'s schemes in order to defeat the KCI attack. On top of justifying our improvements, we further present a detailed security analysis to ensure that the desired security attributes: deniability and authenticity remain preserved.
Authenticated Key Exchange (AKE) is a cryptographic protocol to share a common session key among multiple parties. At ISC 2021, Liu, Tang, and Zhou proposed a modular multi-factor AKE framework resilient to a characteristic attack called server compromise impersonation based on big data in the bounded-retrieval model and concrete post-quantum big data-based AKE schemes. They also formulated a security model (LTZ model) that captures perfect forward secrecy, key compromise impersonation, and server compromise impersonation. However, the LTZ model does not consider the compromise of ephemeral secret keys, and their schemes rely on the random oracle model. In this paper, we extend the LTZ model (LTZ-eCK model) to capture the compromise of ephemeral secret keys and propose a generic construction of big data-based AKE resilient to both server compromise impersonation and ephemeral key leakage in the standard model. Our generic construction allows us to achieve the post-quantum big data-based AKE scheme (from isogenies, lattice, etc.) in the LTZ-eCK model without random oracles.
Identity-based authenticated key exchange (ID-AKE) protocol is an important cryptographic primitive, which is used to establish a session key between two communication participants while authenticating each other. Indeed, most of the existing ID-AKE protocols do not concern with side-channel attacks in the sense that adversaries could obtain partial information of ephemeral/permanent secret keys of users. Recently, several leakage-resilient ID-AKE (LR-ID-AKE) protocols have been proposed to address such attacks. However, these LR-ID-AKE protocols have a restriction that the total leakage information during the life time of the LR-ID-AKE protocol must be bounded to some ratio of ephemeral/permanent secret keys. In this paper, the authors define a new adversary model, termed as identity-based continuous-leakage extended Canetti-Krawczyk (ID-CL-eCK) model. Using the key refreshing procedure (i.e., the multiplicative blinding technique) of permanent secret keys, the first LR-ID-AKE protocol resilient to continuous key leakage is proposed, and it possesses overall unbounded leakage property. Comparisons are given to demonstrate that the proposed protocol is better than the previously proposed ID-AKE protocols in terms of security models and leakage properties. Under the generic bilinear group model, security analysis is made to show that the proposed LR-ID-AKE protocol is secure against adversaries in the new ID-CL-eCK model.