ABSTRACT BASED CRYPTOGRAPHY

The issues of confidentiality, authenticity and anonymity have been known from long time in Security i.e. Cryptography , and the idea of provable security is the basic foundation for most, if not all, latest cryptographic research. With highly advance and improved technology, there is also a need to define these me thods of security under various approaches. One such current approach of security is the attribute based view that has been established by the requirements in a distributed setting. Attribute based encryption and signature concept have been developed in or der to give a more better grained access control. Currently attribute - based method have large area applicability in a number of new decentralized settings and address some already exciting problems. In this thesis we studied an efficient attribute - based en cryption(ABE) method , with support for multi - level threshold predicates. We also discuss regarding the security of some attribute - based signature(ABS) schemes and give the implementation for a threshold ABS method based on a novel approach. In this paper we first look at ABE. Anonymous access control is a highly required property in various applications, e.g. encrypted data in distributed Systems; and attribute based encryption method is a cryptographic methods that is targeted to achieve this property. A BE is an encryption mechanism that is helpful in settings where the list of users may not be known apriority. Here, all users may possess some credentials, and these are used to know access control and also give a reasonable degree of anonymity with respec t to the user’s identity. Cipher text policy attribute based encryption is a scheme that gives a natural way to separate the credentials from the access policy and cleverly combine them at a later stage to provide secure access to protected data. In most A BE schemes the size of the cipher text is quite large and is of the order of the number of attributes. In this work we present our approach for a multi - level threshold attribute based encryption which is independent of the number of attributes.