Practical Attribute-Based Encryption: Traitor Tracing, Revocation and Large UniverseaEuro

A blackbox traceable Attribute-Based Encryption (ABE) can identify a malicious user called traitor, which created a decryption box with respect to an attribute set (respectively, access policy), out of all the users who share the same attribute set (respectively, access policy). However, none of the existing traceable ABE schemes can also support revocation and large attribute universe, that is, being able to revoke compromised keys, and can take an exponentially large number of attributes. In this paper, we formalize the definitions and security models, and propose constructions of both Ciphertext-Policy ABE and Key-Policy ABE that support (i) public and fully collusion-resistant blackbox traceability, (ii) revocation, (iii) large universe and (iv) any monotonic access structures as policies (i.e. high expressivity). We also show that the schemes are secure and blackbox traceable in the standard model against selective adversaries.