Scalable Policy Based Cryptography using ROBDD

Abstract

Policy-based cryptography is a cryptographic method which makes possible to perform policy enforcement in large-scale open environments. Policy based cryptosystems have data minimization principle that strictly ensures that only the necessary information is encrypted. In open computing environments, many interactions occur between the entities from different domains without pre-existing trust relationships which may require the exchange of sensitive resources and hence they need to be carefully protected through clear and concise policies.

The policy-based cryptography uses a digital credential which is basically a digitally signed assertion by a trusted authority of a specific user. The policy-based crypto-systems suffer from the problems like scalability and are not suitable in a multilevel hierarchal structure.

In the present policy based crypto-system the policies are strictly defined using the monotone binary expressions. The min-terms and the max-terms defined in such expressions always produce multiple and redundant optimized policy, which need to change dynamically upon adding or removing the users. This task has been simplified in the present work with the use of Reduced Ordered Binary Decision Diagrams (ROBDD). The policies defined using the ROBDD can ensure that the system is flexible and scalable. ROBDD has another advantage of reducing the decision of resolving the policies amongst the communicating parties.






References:


1. S.S. Al-Riyami, J. Malone-Lee, and N.P. Smart. Escrow-free encryption supporting 
    cryptographic workflow. Cryptology ePrint Archive, Report 2004/258, 2004.
    http://eprint.iacr.org/


2. Establishment of Ad-Hoc Communities through Policy-Based Cryptography-Walid Bagga
    http://www.argreenhouse.com/society/wcan06/wcan06s4p2.pdf


3. http://en.wikipedia.org/wiki/Binary_decision_diagram