Cryptology ePrint Archive: Report 2015/491

Re-encryption, functional re-encryption, and multi-hop re-encryption: A framework for achieving obfuscation-based security and instantiations from lattices

Nishanth Chandran and Melissa Chase and Feng-Hao Liu and Ryo Nishimaki and Keita Xagawa

Abstract: In this work we define multiple relaxations to the definition of correctness in secure obfuscation. While still remaining meaningful, these relaxations provide ways to obfuscate many primitives in a more direct and efficient way. In particular, we first show how to construct a secure obfuscator for the re-encryption primitive from the Decisional Learning with Errors (DLWE) assumption, without going through fully homomorphic encryption. This can be viewed as a meaningful way to trade correctness for efficiency.

Next, we show how our tools can be used to construct secure obfuscators for the functional re-encryption and multi-hop unidirectional re-encryption primitives. In the former case, we improve upon the efficiency of the only previously known construction that satisfies the stronger notion of collusion-resistant obfuscation (due to Chandran et al. - TCC 2012) and obtain a construction with input ciphertexts of constant length. In the latter case, we provide the first known obfuscation-based definition and construction; additionally, our scheme is the first scheme where the size of the ciphertexts does not grow with every hop.

Category / Keywords: public-key cryptography / re-encryption, average-case obfuscation

Original Publication (in the same form): IACR-PKC-2014

Date: received 22 May 2015

Contact author: melissac at microsoft com

Available format(s): PDF | BibTeX Citation

Version: 20150525:144721 (All versions of this report)

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