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 protoc...

The Diffie-Hellman key exchange scheme is a standard component of cryptographic protocols. In this paper, we propose a way in which protocols that use this computational primitive can be verified using formal methods. In particular, we separate the computational aspects of such an analysis from the formal aspects. First, we use Strand Space terminology to define a security condition that summar...

In this paper, we describe a brand new key exchange protocol based on a semidirect product of (semi)groups (more specifically, on extension of a (semi)group by automorphisms), and then focus on practical instances of this general idea. Our protocol can be based on any group, in particular on any non-commutative group. One of its special cases is the standard Diffie-Hellman protocol, which is ba...

One of the most famous key exchange protocols is Diffie-Hellman Protocol (DHP) which a widely used technique on systems around world depend. This protocol simple and uncomplicated, its robustness based Discrete Logarithm Problem (DLP). Despite this, he considered weak against man-in-the-middle attack. article presents completely different version DHP protocol. The proposed two verification stag...

The Diffie Hellman key exchange and the ElGamal oneway trapdoor function are the basic ingredients of public key cryptography. Both these protocols are based on the hardness of the discrete logarithm problem in a finite ring. In this paper we show how the action of a ring on a module gives rise to a generalized Diffie-Hellman and ElGamal protocol. This leads naturally to a cryptographic protoco...

In this paper we study a key exchange protocol similar to DiffieHellman key exchange protocol using abelian subgroups of the automorphism group of a non-abelian nilpotent group. We also generalize group no.92 of HallSenior table [15], for arbitrary prime p and show that for those groups, the group of central automorphisms commute. We use these for the key exchange we are studying. MSC: 94A62, 2...

A key agreement protocol is the most important part to establish a secure cryptographic system and the effort to standardize the key agreement protocols is in rapid progress. Several efficient and secure key agreement protocols have been proposed so far since Diffie-Hellman proposed a public key agreement system in 1976. But, since Diffie-Hellman based key agreement protocols need a lot of comp...