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Tweaking TBE/IBE to PKE transforms with chameleon hash functions. (English) Zbl 1214.94058
Katz, Jonathan (ed.) et al., Applied cryptography and network security. 5th international conference, ACNS 2007, Zhuhai, China, June 5–8, 2007. Proceedings. Berlin: Springer (ISBN 978-3-540-72737-8/pbk). Lecture Notes in Computer Science 4521, 323-339 (2007).
Summary: We present two transforms to acquire chosen ciphertext security from tag based techniques. The first one requires the separability of underlying primitives. By separability, informally, we mean the encryption algorithm has special structures and can process the identity and the message independently. Compared with generic transforms [D. Boneh et al., “Chosen-ciphertext security from identity-based encryption”, SIAM J. Comput. 36, No. 5, 1301–1328 (2006; Zbl 1138.94010)], it significantly reduces the ciphertext size overhead with only marginal computation cost. Compared with [X. Boyen, Q. Mei and B. Waters, “Direct chosen ciphertext security from identity-based techniques”, in: ACM CCS’05. New York: ACM Press, 320–329 (2005)], the only known technique which directly achieves chosen ciphertext secure public key encryption from separable identity based primitives, it only requires selective-Tag/ID security of underlying primitives. Our second transform is less efficient but performs generically. Both transforms preserve the public verifiability of underlying primitives, and can be extended to hierarchical identity based encryption (HIBE) and threshold settings. As an independent interest, we also investigate the security requirements of chameleon hash functions to build strongly unforgeable one-time signatures.
For the entire collection see [Zbl 1121.94002].

94A60 Cryptography
94A62 Authentication, digital signatures and secret sharing
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