Broadcast Steganography

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Abstract

We initiate the study of steganography (BS), an extension of steganography to the multi-recipient setting. BS enables a sender to communicate covertly with a dynamically designated set of receivers, so that the recipients recover the original content, while unauthorized users and outsiders remain unaware of the covert communication. One of our main technical contributions is the introduction of a new variant of anonymous broadcast encryption that we term outsider-anonymous broadcast encryption with pseudorandom ciphertexts((oABE$). Our oABE$ construction achieves sublinear ciphertext size and is secure in the standard model. Besides being of interest in its own right, oABE$ enables an efficient construction of BS secure in the standard model against adaptive adversaries with sublinear communication complexity.