Cryptology ePrint Archive: Report 2016/524

Single-Key to Multi-Key Functional Encryption with Polynomial Loss

Sanjam Garg and Akshayaram Srinivasan

Abstract: Functional encryption (FE) enables fine-grained access to encrypted data. In a FE scheme, the holder of a secret key $\SK_f$ (associated with a function $f$) and a ciphertext $c$ (encrypting plaintext $x$) can learn $f(x)$ but nothing more.

An important parameter in the security model for FE is the number of secret keys that adversary has access to. In this work, we give a transformation from a FE scheme for which the adversary gets access to a single secret key (with ciphertext size sub-linear in the circuit for which this secret key is issued) to one that is secure even if adversary gets access to an {unbounded} number of secret keys. A novel feature of our transformation is that its security proof incurs only a {\em polynomial} loss.

Category / Keywords: public-key cryptography / Functional Encryption, IND-based security, generic transforms

Original Publication (with minor differences): IACR-TCC-2016

Date: received 27 May 2016, last revised 22 Aug 2016

Contact author: akshayaram at berkeley edu

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Version: 20160823:022352 (All versions of this report)

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