In this paper we study security definitions for authenticated key exchange (AKE) protocols.

Abstract. KEA is a Diffie-Hellman based key-exchange protocol developed by NSA which provides mutual authentication for the parties. It became publicly available in 1998 and since then it was neither attacked nor proved to be secure. We analyze the security of KEA and find that the original protocol is susceptible to a class of attacks. On the positive side, we present a simple modification of the protocol which makes KEA secure. We prove that the modified protocol, called KEA+, satisfies the strongest security requirements for authenticated key-exchange and that it retains some security even if a secret key of a party is leaked. Our security proof is in the random oracle model and uses the Gap Diffie-Hellman assumption. Finally, we show how to add a key confirmation feature to KEA+ (we call the version with key confirmation KEA+C) and discuss the security properties of KEA+C. 1

LaMacchia, Lauter and Mityagin recently presented a strong security definition for authenticated key agreement strengthening the well-known Canetti-Krawczyk definition. They also described a protocol, called NAXOS, that enjoys a simple security proof in the new model. Compared to MQV and HMQV, NAXOS is less efficient and cannot be readily modified to obtain a one-pass protocol. On the other hand MQV does not have a security proof, and the HMQV security proof is extremely complicated. This paper proposes a new authenticated key agreement protocol, called CMQV (‘Combined’ MQV), which incorporates design principles from MQV, HMQV and NAXOS. The new protocol achieves the efficiency of HMQV and admits a natural one-pass variant. Moreover, we present a relatively simple and intuitive proof that CMQV is secure in the LaMacchia-Lauter-Mityagin model.

Proofs are invaluable tools in assuring protocol implementers about the security properties of protocols. However, several instances of undetected flaws in the proofs of protocols (resulting in flawed protocols) undermine the credibility of provably-secure protocols. In this work, we examine several protocols with claimed proofs of security by Boyd & González Nieto (2003), Jakobsson & Pointcheval (2001), and Wong & Chan (2001), and an authenticator by Bellare, Canetti, & Krawczyk (1998). Using these protocols as case studies, we reveal previously unpublished flaws in these protocols and their proofs. We hope our analysis will enable similar mistakes to be avoided in the future.

Abstract. The HMQV protocols are ‘hashed variants ’ of the MQV key agreement protocols. They were introduced at CRYPTO 2005 by Krawczyk, who claimed that the HMQV protocols have very significant advantages over their MQV counterparts: (i) security proofs under reasonable assumptions in the (extended) Canetti-Krawczyk model for key exchange; and (ii) superior performance in some situations. In this paper we demonstrate that the HMQV protocols are insecure by presenting realistic attacks in the Canetti-Krawczyk model that recover a victim’s static private key. We propose HMQV-1, patched versions of the HMQV protocols that resists our attacks (but do not have any performance advantages over MQV). We also identify some fallacies in the security proofs for HMQV, critique the security model, and raise some questions about the assurances that proofs in this model can provide. 1.

In the pre-specified peer model for key agreement, it is assumed that a party knows the identifier of its intended communicating peer when it commences a protocol run. On the other hand, a party in the post-specified peer model for key agreement does not know the identifier of its communicating peer at the outset, but learns the identifier during the protocol run. In this paper we compare the security assurances provided by the Canetti-Krawczyk security definitions for key agreement in the pre- and post-specified peer models. We give examples of protocols that are secure in one model but insecure in the other. We also enhance the Canetti-Krawczyk security models and definitions to encompass a class of protocols that are executable and secure in both the pre- and post-specified peer models.

[1,2], a new security model for authenticated key exchange protocols (eCK) is proposed. The new model is suggested to be at least as strong as previous models for key exchange protocols. The model includes a new notion of an Ephemeral Key Reveal adversary query, which is claimed in e. g. [2–4] to be at least as strong as the Session-state Reveal query. We show that Session-state Reveal is stronger than Ephemeral Key Reveal, implying that the eCK security model is incomparable to the CK model [5, 6]. In particular we show that the proposed NAXOS protocol from [1, 2] does not meet its security requirements if the Session-state Reveal query is allowed in the eCK model. We discuss the implications of our result for some related protocols proven correct in the eCK model, and discuss the interaction between Session-state Reveal and protocol transformations.

Key agreement protocols are a fundamental building block for ensuring authenticated and private communications between two parties over an insecure network. This paper focuses on key agreement protocols in the asymmetric authentication model, wherein parties hold a public/private key pair. In particular, we consider a type of known key attack called key compromise impersonation that may occur once the adversary has obtained the private key of an honest party. This attack

In this paper we overview a large number of currently known group key ex-change protocols while focusing on the protocols designed for more than three par-ticipants (for an overview of two- and three-party key exchange protocols we refer to [BM03, DB05c]). For each mentioned protocol we briefly describe the current state of security based on the original analysis as well as later results appeared in the liter-ature. We distinguish between (i) protocols with heuristic security arguments based on informally defined security requirements and (ii) protocols that have been proven secure in one of the existing security models for group key exchange. Note, this paper continues the work started in [Man06] which provides an analytical survey on security requirements and currently known models for group key exchange. We emphasize that the following survey focuses on the security aspects of the protocols and does not aim to provide any efficiency comparison. The reader interested in this kind of surveys we

The GSM network with the greatest worldwide number of users, succumbs to several security vulnerabilities. The short message service (SMS) is one of its superior and well-tried services with a global availability in the GSM networks. The main contribution of this paper is to introduce a new secure application layer protocol, called SSMS, to efficiently embed the desired security attributes in the SMS messages to be used as a secure bearer in the m-payment systems. SSMS efficiently embeds the confidentiality, integrity, authentication, and non-repudiation in the SMS messages. It provides an elliptic curve-based public key solution that uses public keys for the secret key establishment of a symmetric encryption. It also provides the attributes of public verification and forward secrecy. It efficiently makes the SMS messaging suitable for the m-payment applications where the security is the great concern.