## Cryptology ePrint Archive: Report 2009/428

Efficiently from Semi-honest to Malicious OT via OLFE

Jürg Wullschleger

Abstract: A combiner securely implements a functionality out of a set implementations of another functionality from which some may be insecure. We present two efficient combiners for oblivious linear function evaluation (OLFE). The first is a constant-rate OLFE combiner in the semi-honest model, the second combiner implements Rabin string oblivious transfer (RabinOT) from OLFE in the malicious model.

As an application, we show a very efficient reductions in the malicious model of RabinOT over strings to one-out-of-two oblivious transfer over bits (OT) that is only secure in the semi-honest model. For string of size $\ell = \omega(k^2)$, our reductions uses only $4 \ell + o(\ell)$ instances of OT, while previous results required $\Omega(\ell k^2)$. Our new reduction leads to an efficiency improvement for general multi-party computation (MPC) based on semi-honest OT, and makes it almost as efficient as MPC based on malicious OT.

All reductions are unconditionally secure, black-box, universally composable and secure against adaptive adversaries.

Category / Keywords: cryptographic protocols / oblivious transfer, multi-party computation, black-box reductions, combiners, universal composability

Date: received 2 Sep 2009

Contact author: j wullschleger at bristol ac uk

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2009/428

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