In many content distribution systems it is important both to restrict access to content to authorized users and to protect the identities of these users. We discover that current systems for encrypting content to sets of users are subject to attacks on user privacy. We propose a new mechanism, private broadcast encryption, to protect the privacy of users of encrypted file systems and content de...

Broadcast Encryption schemes enable a center to broadcast encrypted programs so that only designated subsets of users can decrypt each program. The stateless variant of this problem provides each user with a fixed set of keys which is never updated. The best scheme published so far for this problem is the “subset difference” (SD) technique of Naor Naor and Lotspiech, in which each one of the n ...

In a predicate encryption scheme an authority generates master public and secret keys, and uses the master secret key to derive personal secret keys for authorized users. Each user’s personal secret key SKf corresponds to a predicate f defining the access rights of that user, and each ciphertext is associated (by the sender) with an attribute. The security provided is that a ciphertext associat...

A proxy re-encryption (PRE) scheme supports the delegation of decryption rights via a proxy, who makes the ciphertexts decryptable by the delegatee. PRE is useful in various applications such as encrypted email forwarding. In this paper, we introduce a more generalized notion of conditional proxy broadcast re-encryption (CPBRE). A CPBRE scheme allows Alice to generate a re-encryption key for so...

The problem we address is how to communicate securely with a set of users (the target set) over an insecure broadcast channel. In order to solve this problem, several broadcast encryption schemes have been proposed. In these systems, the parameters of major concern are the length of transmission and number of keys held by each user's set top terminal (STT). Due to the need to withstand hardware...

We rst present two tight lower bounds on the size of the secret keys of each user in an unconditionally secure one-time use broadcast encryption scheme (OTBES). Then we show how to construct a computa-tionally secure multiple-use broadcast encryption scheme (MBES) from a key predistribution scheme (KPS) by using the ElGamal cryptosystem. We prove that our MBES is secure against chosen (message,...

This paper describes the first identity-based broadcast encryption scheme (IBBE) with constant size ciphertexts and private keys. In our scheme, the public key is of size linear in the maximal size m of the set of receivers, which is smaller than the number of possible users (identities) in the system. Compared with a recent broadcast encryption system introduced by Boneh, Gentry and Waters (BG...

Broadcast encryption provides an efficient way to encrypt a message for a large number of receivers. This paper investigates whether it is possible to further improve efficiency of an existing state-of-the-art broadcast encryption scheme by re-using a subset of the random choices among different encryptions, without compromising the security of the original scheme. We introduce two schemes: the...

Multi-service oriented broadcast encryption is a mechanism that allows a center to securely distribute multiple services to its authorized users. In this paper, we suggest a framework called M framework from the subset cover method [12] using RSA exponentiation technique. In this framework, each user’s secret storage is independent of the number of services. Service subscriptions and service pr...