Milinda Perera 	

Outsider-Anonymous Broadcast Encryption

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, we propose the first broadcast encryption scheme with
sublinear ciphertexts to attain meaningful guarantees of receiver
anonymity.  We 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. We also describe
two constructions with enhanced decryption, one under the gap
Diffie-Hellman assumption, in the random oracle model, and the other
under the decisional Diffie-Hellman assumption, in the standard model.

Joint work with Nelly Fazio.