Cryptology ePrint Archive: Report 2014/598

Privacy-Free Garbled Circuits with Applications To Efficient Zero-Knowledge

Tore Kasper Frederiksen and Jesper Buus Nielsen and Claudio Orlandi

Abstract: In the last few years garbled circuits (GC) have been elevated from being merely a compo- nent in Yao’s protocol for secure two-party computation, to a cryptographic primitive in its own right, following the growing number of applications that use GCs. Zero-Knowledge (ZK) protocols is one of these examples: In a recent paper Jawurek et al. [JKO13] showed that GCs can be used to construct efficient ZK proofs for unstructured languages. In this work we show that due to the property of this particular scenario (i.e., one of the parties knows all the secret input bits, and therefore all intermediate values in the computation), we can construct more efficient garbling schemes specifically tailored to this goal. As a highlight of our result, in one of our constructions only one ciphertext per gate needs to be communicated and XOR gates never require any cryptographic operations. In addition to making a step forward towards more practical ZK, we believe that our contribution is also interesting from a conceptual point of view: in the terminology of Bellare et al. [BHR12] our garbling schemes achieve au- thenticity, but no privacy nor obliviousness, therefore representing the first natural separation between those notions.

Category / Keywords: cryptographic protocols / zero-knowledge, garbled circuits

Original Publication (with minor differences): IACR-EUROCRYPT-2015

Date: received 4 Aug 2014, last revised 11 May 2015

Contact author: orlandi at cs au dk

Available format(s): PDF | BibTeX Citation

Note: Fixed typos and minor corrections.

Version: 20150511:160916 (All versions of this report)

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