## Cryptology ePrint Archive: Report 2016/848

From Weakly Selective to Selective Security in Compact Functional Encryption, Revisited

Linfeng Zhou

Abstract: We provide a generic transformation from weakly selective secure $\mathsf{FE}$ to selective secure $\mathsf{FE}$ through an approach called \textit{hybrid functional key generation}. Furthermore, our transformation preserves the compactness of the $\mathsf{FE}$ scheme. Additionally, we note that this transformation is much simpler than the prior work \cite{garg2016single}. We consider the simplicity of the construction in this work as a positive feature and the hybrid functional key generation approach as a new method that can be applied in functional encryption schemes. Furthermore, we try to weaken the input $\mathsf{FE}$ scheme of our transformation to be a non-compact one instead of a fully-compact one, by additionally assuming the hardness of LWE (or Ring-LWE) assumption. We achieve this result by utilizing the $\mathsf{FE}$ scheme for bounded collusions with \textit{decomposable and succinct ciphertext property}, which can be solely based on the LWE (or Ring-LWE) assumption. Finally we present the implications of our result, which improves previous results, in building general-purpose indistinguishability obfuscator from (well-expressed) functional encryption.

Category / Keywords: Functional Encryption, Minimal Assumptions, Weakly Selective Security, Selective Security, iO

Date: received 2 Sep 2016, last revised 17 Feb 2017

Contact author: daniel linfeng zhou at gmail com

Available format(s): PDF | BibTeX Citation

Note: Extended results.

Short URL: ia.cr/2016/848

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