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IEEE Information Theory Workshop (ITW)

Pairwise Oblivious Transfer

Rémi A. Chou

Published Apr 11, 2021• 11 citations
Publisher

Abstract

We consider oblivious transfer between one client and two non-colluding servers that store independent contents. The client requests one file from each server such that (i) the servers do not learn the file selection of the client, and (ii) the client does not learn information about the non-selected files. We show under the honest-but-curious assumption that oblivious transfer with non-zero rates can be achieved with a multiuser protocol between the client and the servers. This contrasts with the case where the client engages in independent protocols with each of the two servers, for which it is known that oblivious transfer with information-theoretic security is impossible in the absence of additional resources. Furthermore, we derive a capacity result for the proposed setting.

DOI
10.1109/itw46852.2021.9457601

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We consider oblivious transfer between one client and two non-colluding servers that store independent contents. The client requests one file from each server such that (i) the servers do not learn the file selection of the client, and (ii) the client does not learn information about the non-selected files. We show under the honest-but-curious assumption that oblivious transfer with non-zero rates can be achieved with a multiuser protocol between the client and the servers. This contrasts with the case where the client engages in independent protocols with each of the two servers, for which it is known that oblivious transfer with information-theoretic security is impossible in the absence of additional resources. Furthermore, we derive a capacity result for the proposed setting.
In this paper, we study the information-theoretic limits of oblivious transfer via noisy channels. We also investigate oblivious transfer over a noisy multiple-access channel with two non-colluding senders and a single receiver. The channel is modeled through correlations among the parties, who may be honest-but-curious or, in the case of the receiver, potentially malicious. We first revisit the information-theoretic limits of two-party oblivious transfer and then extend these results to the multiple-access setting. For honest-but-curious participants, we introduce a multiparty protocol that reduces a general multiple access channel to a suitable correlation model. In scenarios with a malicious receiver, we characterize an achievable oblivious transfer rate region.
We consider the problem of oblivious transfer (OT) over OFDM and MIMO wireless communication systems where only the receiver knows the channel state information. The sender and receiver also have unlimited access to a noise-free real channel. Using a physical layer approach, based on the properties of the noisy fading channel, we propose a scheme for honest-but-curious parties that enables the transmitter to send obliviously one-of-two files, i.e., without knowing which one has been actually requested by the receiver, while also ensuring that the receiver does not get any information about the other file.
Abstract Oblivious transfer is considered as a cryptographic primitive task for quantum information processing over a quantum network. It is an essential building block for secure multiparty computation. It is known that one‐server oblivious transfer is impossible. When the task is the transmission of classical messages, protocols for two‐server oblivious transfer exist, i.e., existing protocols work under the assumption that two servers do not communicate with each other. However, when the task is the transmission of a quantum state, no existing method works even under the above two‐server assumption. Two‐server oblivious transfer protocols for quantum messages are proposed for the first time.
We study the following private data transfer problem: Alice has a database of files. Bob and Cathy want to access a file each from this database (which may or may not be the same file), but each of them wants to ensure that their choices of file do not get revealed even if Alice colludes with the other user. Alice, on the other hand, wants to make sure that each of Bob and Cathy does not learn any more information from the database than the files they demand (the identities of which will be unknown to her). Moreover, they should not learn any information about the other files even if they collude. It turns out that it is impossible to accomplish this if Alice, Bob, and Cathy have access only to private randomness and noiseless communication links. We consider this problem when a binary erasure broadcast channel with independent erasures is available from Alice to Bob and Cathy in addition to a noiseless public discussion channel. We study the file-length-per-broadcast-channel-use rate in the honest-but-curious model. We focus on the case when the database consists of two files, and obtain the optimal rate. We then extend to the case of larger databases, and give upper and lower bounds on the optimal rate.
Both the oblivious transfer (OT) problem and the symmetric private information retrieval (SPIR) problem studies the scenario where a client retrieves information privately and securely from databases, i.e., the privacy of the client is protected from the databases, and the undesired information is protected from the client. The OT problem studies the case of one database plus additional noisy resources between the database and the client. The SPIR problem studies the case of multiple replicated and non-colluding databases. In this paper, we combine the two models and propose a new problem of oblivious transfer (OT) with two replicated databases and a binary erasure multiple access channel connecting the databases and the client. We first provide an upper bound on the OT capacity. We then propose a protocol which achieves the upper bound. Therefore, we obtain the capacity of OT for this model. In our achievability and converse proofs, we utilized the techniques from both traditional OT and PIR. Compared to schemes that utilizes only techniques from OT, we see a 100% increase in the achieved OT rate.
Assume A owns t secret k-bit strings. She is willing to disclose one of them to B, at his choosing, provided he does not learn anything about the other strings. Conversely, B does not want A to learn which secret he chose to learn. A protocol for the above task is said to implement one-out-of-t string oblivious transfer, denoted (/sup t//sub 1/)-OT/sup k//sub 2/. This primitive is particularly useful in a variety of cryptographic settings. An apparently simpler task corresponds to the case k=1 and t=2 of two 1-bit secrets: this is known as one-out-of-two bit oblivious transfer, denoted (/sup 2//sub 1/)-OT/sub 2/. We address the question of implementing (/sup t//sub 1/)-OT/sup k//sub 2/ assuming the existence of a (/sup 2//sub 1/)-OT/sub 2/. In particular, we prove that unconditionally secure (/sup 2//sub 1/)-OT/sup k//sub 2/ can be implemented from /spl Theta/(k) calls to (/sup 2//sub 1/)-OT/sub 2/. This is optimal up to a small multiplicative constant. Our solution is based on the notion of self-intersecting codes. Of independent interest, we give several efficient new constructions for such codes. Another contribution of this paper is a set of information-theoretic definitions for correctness and privacy of unconditionally secure oblivious transfer.