New Constructions and Proof Methods for Large Universe Attribute-Based Encryption.

Abstract

We propose two large universe Attribute-Based Encryption constructions. In a large universe ABE construction any string can be used as an attribute and attributes need not be enumerated at system setup. Our first construction establishes a novel large universe Ciphertext-Policy ABE scheme on prime order bilinear groups, while the second achieves a significant efficiency improvement over the large universe Key-Policy ABE systems of Lewko-Waters and Lewko. Both schemes are selectively secure in the standard model under two “q-type ” assumptions similar to ones used in prior works. Our work brings back “program and cancel ” techniques to this problem. We provide implementations and benchmarks of our constructions in Charm; a programming environment Traditionally, public key encryption schemes provided any user with the ability to share data with another specific user in a private manner. However, in many applications we would like to have the additional capability to encrypt data for a set of users according to a specific policy on their credentials. For example, one might want to store data in a public server such that only parties with credentials of specific forms are