ProvablySecure Authenticated Group Diffie-Hellman Key Exchange

Abstract: Authenticated key exchange protocols allow two participants A and B, communicating over a public network and each holding an authentication means, to exchange a shared secret value. Methods designed to deal with this cryptographic problem ensure A (resp. B) that no other participants aside from B (resp. A) can learn any information about the agreed value, and often also ensure A and B that their respective partner has actually computed this value. A natural extension to this cryptographic method is to consider a pool of participants exchanging a shared secret value and to provide a formal treatment for it. Starting from the famous 2-party Diffie-Hellman (DH) key exchange protocol, and from its authenticated variants, security experts have extended it to the multi-party setting for over a decade and completed a formal analysis in the framework of modern cryptography in the past few years. The present paper synthesizes this body of work on the provably-secure authenticated group DH key exchange. The present paper revisits and combines the full versions of the following four papers

Security proofs for an efficient password-based key exchange

Abstract. Password-based key exchange schemes are designed to provide entities communicating over a public network, and sharing a (short) password only, with a session key (e.g, the key is used for data integrity and/or confidentiality). The focus of the present paper is on the analysis of very efficient schemes that have been proposed to the IEEE P1363 Standard working group on password-based authenticated key-exchange methods, but for which actual security was an open problem. We analyze the AuthA key exchange scheme and give a complete proof of its security. Our analysis shows that the AuthA protocol and its multiple modes of operation are provably secure under the computational Diffie-Hellman intractability assumption, in both the random-oracle and the ideal-cipher models.

A Practical Approach to the InterGroup Protocols

Existing reliable ordered group communication protocols have been developed for local-area networks and do not, in general, scale well to large numbers of nodes and wide-area networks. The InterGroup suite of protocols is a scalable group communication system that introduces an unusual approach to handling group membership, and supports a receiver-oriented selection of service. The protocols are intended for a wide-area network, with a large number of nodes, that has highly variable delays and a high message loss rate, such as the Internet. The levels of the message delivery service range from unreliable unordered to reliable timestamp ordered. We also present a secure group layer that builds on InterGroup to provide SSL-like security for groups

Letter to the editor: acute myeloid leukemia cells exhibit selective down-regulation of DNMT3A isoform 2

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An Integrated Solution for Secure Group Communication in Wide-Area Networks

Many distributed applications require a secure reliable group communication system to provide coordination among the application components. This paper describes a secure group layer (SGL) which bundles a reliable group communication system, a group authorization and access control mechanism, and a group key agreement protocol to provide a comprehensive and practical secure group communication platform. SGL also encapsulates the standard message security services (i.e, confidentiality, authenticity and integrity). A number of challenging issues encountered in the design of SGL are brought to light and experimental results obtained with a prototype implementation are discussed

How to extract and expand randomness: a summary and explanation of existing results

We examine the use of randomness extraction and expansion in key agreement (KA) pro- tocols to generate uniformly random keys in the standard model. Although existing works provide the basic theorems necessary, they lack details or examples of appropriate cryptographic primitives and/or parameter sizes. This has lead to the large amount of min-entropy needed in the (non-uniform) shared secret being overlooked in proposals and efficiency comparisons of KA protocols. We therefore summa- rize existing work in the area and examine the security levels achieved with the use of various extractors and expanders for particular parameter sizes. The tables presented herein show that the shared secret needs a min-entropy of at least 292 bits (and even more with more realistic assumptions) to achieve an overall security level of 80 bits using the extractors and expanders we consider. The tables may be used to �nd the min-entropy required for various security levels and assumptions. We also �nd that when using the short exponent theorems of Gennaro et al., the short exponents may need to be much longer than they suggested