The document discusses secure multi-owner data sharing for dynamic groups in clouds. It outlines Mona, a scheme that uses dynamic broadcast encryption for access control and group signatures for authentication. Mona allows efficient revocation without updating other users' keys and supports anonymity and traceability. The document compares Mona to other schemes and finds Mona addresses issues around identity privacy and revocation more effectively. Future work aims to make Mona more reliable and scalable by handling failures of the group manager.