Making Public Key Functional Encryption Function Private, Distributively

Xiong Fan, Qiang Tang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations


We put forth a new notion of distributed public key functional encryption. In such a functional encryption scheme, the secret key for a function f will be split into shares skif. Given a ciphertext ct that encrypts a message x, a secret key share skif, one can evaluate and obtain a shared value yi. Adding all the shares up can recover the actual value of f(x), while partial shares reveal nothing about the plaintext. More importantly, this new model allows us to establish function privacy which was not possible in the setting of regular public key functional encryption. We formalize such notion and construct such a scheme from any public key functional encryption scheme together with learning with error assumption. We then consider the problem of hosting services in the untrusted cloud. Boneh, Gupta, Mironov, and Sahai (Eurocrypt 2014) first studied such application and gave a construction based on indistinguishability obfuscation. Their construction had the restriction that the number of corrupted clients has to be bounded and known. They left an open problem how to remove such restriction. We resolve this problem by applying our function private (distributed) public key functional encryption to the setting of hosting service in multiple clouds. Furthermore, our construction provides a much simpler and more flexible paradigm which is of both conceptual and practical interests. Along the way, we strengthen and simplify the security notions of the underlying primitives, including function secret sharing.

Original languageEnglish (US)
Title of host publicationPublic-Key Cryptography - PKC 2018 - 21st IACR International Conference on Practice and Theory of Public-Key Cryptography, Proceedings
EditorsMichel Abdalla, Ricardo Dahab
PublisherSpringer Verlag
Number of pages27
ISBN (Print)9783319765778
StatePublished - 2018
Event21st IACR International Conference on Practice and Theory of Public-Key Cryptography, PKC 2018 - Rio de Janeiro, Brazil
Duration: Mar 25 2018Mar 29 2018

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume10770 10769 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other21st IACR International Conference on Practice and Theory of Public-Key Cryptography, PKC 2018
CityRio de Janeiro

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • General Computer Science


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