Replay Attack Prevention in Kerberos Authentication Protocol Using Triple Password

Replay attack and password attacks are serious issues in the Kerberos authentication protocol. Many ideas have been proposed to prevent these attacks but they increase complexity of the total Kerberos environment. In this paper we present an improved method which prevents replay attacks and password attacks by using Triple password scheme. Three passwords are stored on Authentication Server and Authentication Server sends two passwords to Ticket Granting Server (one for Application Server) by encrypting with the secret key shared between Authentication server and Ticket Granting server. Similarly, Ticket Granting Server sends one password to Application Server by encrypting with the secret key shared between TGS and application server. Meanwhile, Service-Granting-Ticket is transferred to users by encrypting it with the password that TGS just received from AS. It helps to prevent Replay attack.