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Fully collusion secure dynamic broadcast encryption with constant-size ciphertexts or decryption keys. (English) Zbl 1151.94502
Takagi, Tsuyoshi (ed.) et al., Pairing-based cryptography – Pairing 2007. First international conference, Tokyo, Japan, July 2–4, 2007. Proceedings. Berlin: Springer (ISBN 978-3-540-73488-8/pbk). Lecture Notes in Computer Science 4575, 39-59 (2007).
Summary: This paper puts forward new efficient constructions for public-key broadcast encryption that simultaneously enjoy the following properties: receivers are stateless; encryption is collusion-secure for arbitrarily large collusions of users and security is tight in the standard model; new users can join dynamically i.e. without modification of user decryption keys nor ciphertext size and little or no alteration of the encryption key.We also show how to permanently revoke any subgroup of users. Most importantly, our constructions achieve the optimal bound of $$O(1)$$-size either for ciphertexts or decryption keys, where the hidden constant relates to a couple of elements of a pairing-friendly group. Our broadcast-KEM trapdoor technique, which has independent interest, also provides a dynamic broadcast encryption system improving all previous efficiency measures (for both execution time and sizes) in the private-key setting.
For the entire collection see [Zbl 1119.94003].

##### MSC:
 94A60 Cryptography 94A62 Authentication, digital signatures and secret sharing
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