Content distribution is an important application domain for cryptographic techniques. Existing security solutions for multi recipient communication, like broadcast encryption, focus mostly on the concerns of the content originator. This project tackles the problem from a broader perspective that includes the privacy concerns of the recipients, and develops cryptographic models and protocols for content distribution that provide guarantees beyond the mere secrecy of the data. The outcomes of this research will enable solutions that address the privacy issues associated with cloud storage. The techniques developed in the course of the research will be stimulating for researchers across the cryptography and information-hiding communities, thus potentially fostering collaborations between the fields.
The project has four specific research objectives: (1) the design of cryptographic constructions for receiver-anonymous broadcast encryption that at once provide transmission secrecy, afford anonymity to the receivers, and enjoy performance comparable to standard broadcast encryption; (2) the exploration of the relationship between receiver anonymity and ciphertext ambiguity, which refers to the possibility that a given ciphertext might appear valid to multiple decryptors; (3) the formulation of the concept of broadcast steganography to enable the use of a broadcast channel as a medium for covert communication; and (4) the investigation of applications like collaborative remote storage, whereby a group of users accesses shared content in the cloud privately and obliviously.
