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

  • Afonso ArriagaEmail author
  • Manuel Barbosa
  • Pooya Farshim
Conference paper
First Online:
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10095)

Abstract

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.

Keywords

Function privacy Functional encryption Obfuscation Keyword search Inner-product encryption 
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Notes

Acknowledgements

Afonso Arriaga was supported by the National Research Fund, Luxembourg (AFR Grant No. 5107187). Manuel Barbosa was funded by project “NanoSTIMA: Macro-to-Nano Human Sensing: Towards Integrated Multimodal Health Monitoring and Analytics/NORTE-01-0145-FEDER-000016”, which is financed by the North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF). Pooya Farshim was supported in part by grant ANR-14-CE28-0003 (Project EnBid).

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Copyright information

© Springer International Publishing AG 2016

Authors and Affiliations

  1. 1.SnT, University of LuxembourgLuxembourg CityLuxembourg
  2. 2.HASLab - INESC TECDCC FC University of PortoPortoPortugal
  3. 3.ENS, CNRS & Inria, PSL Research UniversityParisFrance

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