Date Added: Aug 2012
The authors 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. Their construction establishes a novel large universe Ciphertext-Policy ABE scheme on prime order bilinear groups and the other 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. Their work brings back "program and cancel" techniques to this problem. They provide implementations and benchmarks of their constructions in Charm; a programming environment for rapid prototyping of cryptographic primitives.