Abstract
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In this work, we present an adaptively secure
identity-based broadcast encryption system featuring constant
sized ciphertext in the standard model. The size of the public
key and the private keys of our system are both linear in
the maximum number of receivers. Also, our system is fully
collusion-resistant and has stateless receivers. Compared with the
state-of-the-art, our scheme is well optimized for the broadcast
encryption. The computational complexity of decryption of our
scheme depends only on the number of receivers, not the
maximum number of receivers of the system. Technically, we
employ dual system encryption technique and our proposal
offers adaptive security under the general subgroup decisional
assumption. Our scheme demonstrates that the adaptive security
of the schemes utilizing a composite order group can be proven
under the general subgroup decisional assumption while many
existing systems working in a composite order group are secure
under multiple subgroup decision assumptions. We note that this
finding is of an independent interest, which may be useful in other
scenarios.