A CRYPTOGRAPHIC SCHEME FOR THE TIME DEPENDENT ACCESS IN A HIERARCHY

Abstract

The access control problem in a hierarchical, organization consists of the management of information among a number of users who are divided into different security classes according to their suitability in accessing the information. With in the scope of cryptography the problem can be reduced to generate cryptographic key for each security class in such a way that the cryptographic key of a higher class can be used to derive the keys of all lower security classes. In time dependent cryptographic key assignment scheme the cryptographic keys of a class are different for each time period, that is, the cryptographic key of a class C; at time t is K1,1. Key derivation is constrained not only by the class relation, but also the time period. In this each user holds some secret parameters whose number is independent of the number of classes in the hierarchy and the total time periods. As part of our dissertation we have implemented the time dependent cryptographic scheme by using Lucas functions and SHA —1 as hash function. We presented how this time dependent scheme can be used in the development of cryptographic key back up system. We have also made interfaces that provide the user friendliness. This software is written in Java under Windows environment. 111