In distributed systems users need to share sensitive objects with others based on the recipients' ability to satisfy a policy. Attribute-Based Encryption (ABE) is a new paradigm where such policies are specified and cryptographically enforced in the encryption algorithm itself. Ciphertext-Policy ABE (CP-ABE) is a form of ABE where policies are associated with encrypted data and attributes are associated with keys. In this work we focus on improving the flexibility of representing user attributes in keys. Specifically, we propose Ciphertext Policy Attribute Set Based Encryption (CP-ASBE) - a new form of CP-ABE - which, unlike existing CP-ABE schemes that represent user attributes as a monolithic set in keys, organizes user attributes into a recursive set based structure and allows users to impose dynamic constraints on how those attributes may be combined to satisfy a policy. We show that the proposed scheme is more versatile and supports many practical scenarios more naturally and efficiently. We provide a prototype implementation of our scheme and evaluate its performance overhead.
Rakesh Bobba is a Security Engineer at the National Center for Supercomputing Applications (NCSA), University of Illinois, Urbana-Champaign. His research interests are in distributed system security and critical infrastructure protection. Topics of interest include authentication, access control, key management, security protocols and their formal analysis, and applied cryptography, among others. He is currently involved in the design and development of secure communication and data sharing infrastructures for the next-generation Power Grid, and in the design of secure attribute-based systems.