Date Added: Mar 2012
In the standard setting of broadcast encryption, information about the receivers is transmitted as part of the ciphertext. In several broadcast scenarios, however, the identities of the users authorized to access the content are often as sensitive as the content itself. In this paper, the authors propose the first broadcast encryption scheme with sublinear ciphertexts to attain meaningful guarantees of receiver anonymity. They formalize the notion of outsider-Anonymous Broadcast Encryption (oABE), and describe generic constructions in the standard model that achieve outsider-anonymity under adaptive corruptions in the chosen-plaintext and chosen-ciphertext settings.