Recipient Revocable Broadcast Encryption Schemes Without Random Oracles

Abstract

Public key broadcast encryption system is a fundamental cryptographic primitive that enables a broadcaster to transmit encrypted content to a set of users allowing only a privileged subset of users to decrypt the content. Traditionally, it is not possible to remove any receiver from the encrypted content without decryption. Recipient revocable broadcast encryption (RRBE) is an useful cryptographic primitive whereby a trusted third party can revoke a set of users from the encrypted content without having the ability to decrypt it. This property is not achievable in traditional broadcast encryption (BE) schemes. However, the currently existing RRBE schemes are secure only in the random oracle model. In this paper, we propose two new constructions for RRBE with constant number of pairing, linear exponentiation operations and analyze their security in the standard model. Our first construction achieves adaptive security in the standard model with constant communication cost as opposed to the existing adaptively secure RRBE schemes all of which use random oracles and have linear communication cost. The storage and computation complexity are linear to the total number of users and the number of subscribed users respectively.