In Distributed environment authentication and keyexchange mechanisms plays a major role. Generally in authentication a client and server agree upon a cryptographic key which is mutually exchanged. Earlier passwords were stored in a single server where if an intruder gains access of that server by some malicious attacks then all the passwords stored in the database are to be compromised and therefore the e-commerce application security is endangered. In-order to improve the efficiency and performance of the authentication mechanisms we involve multiple servers to store the passwords and participate in key-exchange and authentication process so as to ensure that even a single server is compromised the whole system's security is not in threat and also generating a nonce values randomly for every session corresponds to a two level security mechanism where the scope of an attacker to pretend as the legitimate user and login into the system is completely restricted.In this model the passwords are stored in their equivalent hash values and they are spitted into multiple servers. Making it even more difficult for the attacker to determine the password even by reverse engineering he cannot intercept the actual password form segments of hash value. Hence, we can present this model as safe and secure password based authentication scheme using key exchange mechanism.

Abstract.We discuss two-party mutual authentication protocols providing authenticated key exchange, focusing on those using asymmetric techniques. A simple, efficient protocol referred to as the station-to-station (STS) protocol is introduced, examined in detail, and considered in relation to existing protocols. The definition of a secure protocol is considered, and desirable characteristics of secure protocols are discussed.

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Akmct-This paper plesenfs a tutorial introduction to contempomy ayptography. The basic information li~eoretic and computational properties of d a d d and modern cryptographic systems are presented, fobwed by uyptanalytic examination of seved important systems and an exlminrtion o f the a p p t i a t i o n of uyptography to the security of timeduring systems and computer networks. The paper concludes with I guide to the cryptographic literature.

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