Authenticated key exchange protocols are a fundamental cryptography building block for establishing a secret shared key among participating parties over an open network model. Mohamed et al. proposed a tightly-secure authenticated key exchange without NAXOS approach based on decision linear problem in order to solve an open problem for designing an authenticated key exchange protocol without using NAXOS trick. Mohamed et al.'s protocol has tight security proof in the eCK model under the random oracle problem and its security claims verified by using the games sequence tool. However, we show that Mohamed et al.'s protocol cannot withstand the key compromise impersonation attacks and man in the middle attacks. Furthermore, Mohamed et al.'s protocol cannot provide an implicit entity authentication property since it is a basic security property for an authenticated key exchange protocol. Therefore, the protocol is not secure in the eCK model.
Authenticated key exchange protocols are a fundamental cryptography building block for establishing a secret shared key among participating parties over an open network model. Mohamed et al. proposed a tightly-secure authenticated key exchange without NAXOS approach based on decision linear problem in order to solve an open problem for designing an authenticated key exchange protocol without using NAXOS trick. Mohamed et al.'s protocol has tight security proof in the eCK model under the random oracle problem and its security claims verified by using the games sequence tool. However, we show that Mohamed et al.'s protocol cannot withstand the key compromise impersonation attacks and man in the middle attacks. Furthermore, Mohamed et al.'s protocol cannot provide an implicit entity authentication property since it is a basic security property for an authenticated key exchange protocol. Therefore, the protocol is not secure in the eCK model.
Design Secure Authenticated Key Exchange (AKE) protocol without NAXOS approach is remaining as an open problem.NAXOS approach [4] is used to hide the ephemeral secret key from an adversary even if the adversary in somehow may obtain the ephemeral secret key.Using NAXOS approach will cause two main drawbacks: (i) leaking of the static secret key which will be utilized in computing the exponent of the ephemeral public key; (ii) maximization of using random oracle when applying to the exponent of the ephemeral public key and session key derivation.In this paper, we present another AKE-secure without NAXOS approach based on decision linear assumption in the random oracle model.We fasten our security using games sequences tool which gives tight security for our protocol.
Two-party key exchange protocol is a mechanism in which two parties communicate with each other over an insecure channel and output the same session key.A key exchange protocol that is secure against an active adversary who can control and modify the exchanged messages is called authenticated key exchange (AKE) protocol.LaMacchia, Lauter and Mityagin presented a strong security definition for public key infrastructure (PKI) based two-pass protocol, which we call the extended Canetti-Krawczyk (eCK) security model, and some researchers have provided eCK-secure AKE protocols in recent years.However, almost all protocols are provably secure in the random oracle model or rely on a special implementation technique so-called the NAXOS trick.In this paper, we present a PKI-based two-pass AKE protocol that is secure in the eCK security model.The security of the proposed protocol is proven without random oracles (under three assumptions), and does not rely on implementation techniques such as the NAXOS trick.
LaMacchia, Lauter and Mityagin presented a strong security model for authenticated key agreement, namely the eCK model. They also constructed a protocol, namely the NAXOS protocol, that enjoys a simple security proof in the eCK model. However, the NAXOS protocol uses a random-oracle-based technique to combine the long-term secret key and the per-session-randomness; so-called NAXOStrick, in order to achieve the eCK security definition. For NAXOS-trick-based protocols, the leakage of per-session-randomness modelled in the eCK model is somewhat unnatural, because the eCK model leaks per-session-randomness, while the output of the NAXOS-trick computation remains safe. In this work, we present a standard model eCK-secure protocol construction, eliminating the NAXOS-trick. Moreover, our protocol is a generic constructions, which can be instantiated with arbitrary suitable cryptographic primitives. Thus, we present a generic eCK-secure, NAXOS-free, standard model key exchange protocol. To the best of our knowledge this is the first paper on generic transformation of a CCA2-secure public key encryption scheme to an eCK-secure key exchange protocol in the standard model.
Nowadays many crucial network applications rely on the existence of a confidential channel established by authenticated key exchange (AKE) protocols over public networks.With the rapid development of cyber technology, novel attacks to cryptosystem emerge in an endless stream.This has also led to the development of AKE solutions to provide increasingly stronger security guarantees.In this thesis we focus on provision of practical constructions for AKE protocols which are provably secure in a strong sense without resorting to random oracles.We first we present three new efficient compilers to generically turn passively secure key exchange protocols (KE) into authenticated key exchange protocols (AKE) where security also holds in the presence of active adversaries.Our compilers are not only a useful tool for the design of new AKE systems with many additional security properties in a modular and less error-prone fashion, but they also help to relax the assumptions on existing, practical key exchange mechanisms which are not known to be provably secure AKE protocols.Security of our compilers is shown in a strong modified CK model where the adversary is allowed to reveal either long-term secret key or state information of the protocol participants.On the second, we study the open problem on constructing eCK secure two party AKE protocol without random oracles and NAXOS trick.A generic construction satisfying those requirements is given based on well-known cryptographic primitives following the guideline of efficiency.Then a concrete protocol is proposed which is the first eCK secure protocol in the standard model under both standard assumptions and post-specified peer setting (i.e.without knowing any cryptographic information about its communication peer).Both proposed schemes can be more efficiently implemented with secure device than previous works which are eCK secure in the standard model, where the secure device might be normally used to store the long-term private key and to implement codes of protocol which need to be resilience of state leakage.Finally, we generalize our one-round two party AKE construction to group case that yields an efficient tripartite AKE protocol based on bilinear maps and a candidate group AKE protocol (with more than three members) based on multilinear maps.Up to now they are the first solutions which can be proved secure in the g-eCK model without random oracles.Meanwhile we make first step to show how to simplify the security proof for one-round group AKE under g-eCK model.i
The extended Canetti–Krawczyk (eCK) security models, are widely used to provide security arguments for authenticated key exchange protocols that capture leakage of various kinds of secret information like the long-term private key and session-specific secret state. In this paper, we study the open problem on constructing eCK secure AKE protocol without random oracles and NAXOS like trick. A generic construction GC-KKN satisfying those requirements is first given relying on standard cryptographic primitives following the guideline of efficiency. On the second a concrete protocol is proposed which is the first eCK secure protocol in the standard model under both standard assumptions and post-specified peer setting. Both proposed schemes can be more efficiently implemented with secure device than previous eCK secure protocols in the standard model, where the secure device might be normally used to store the long-term private key and implement algorithms of protocol which require to be resilience of state leakage.