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Private Functional Encryption: Indistinguishability-Based Definitions and Constructions from Obfuscation

2016; Springer Science+Business Media; Linguagem: Inglês

10.1007/978-3-319-49890-4_13

1611-3349

Afonso Arriaga, Manuel Barbosa, Pooya Farshim,

Privacy-Preserving Technologies in Data

Private functional encryption guarantees that not only the information in ciphertexts is hidden but also the circuits in decryption tokens are protected. A notable use case of this notion is query privacy in searchable encryption. Prior privacy models in the literature were fine-tuned for specific functionalities (namely, identity-based encryption and inner-product encryption), did not model correlations between ciphertexts and decryption tokens, or fell under strong uninstantiability results. We develop a new indistinguishability-based privacy notion that overcomes these limitations and give constructions supporting different circuit classes and meeting varying degrees of security. Obfuscation is a common building block that these constructions share, albeit the obfuscators necessary for each construction are based on different assumptions. In particular, we develop a composable and distributionally secure hyperplane membership obfuscator and use it to build an inner-product encryption scheme that achieves an unprecedented level of privacy, positively answering a question left open by Boneh, Raghunathan and Segev (ASIACRYPT 2013) concerning the extension and realization of enhanced security for schemes supporting this functionality.