Experimental Implementation of Oblivious Transfer in the Noisy Storage Model

Abstract

Cryptography's importance in our everyday lives continues to grow in our increasingly digital world. Oblivious transfer (OT) has long been a fundamental and important cryptographic primitive since it is known that general two-party cryptographic tasks can be built from this basic building block. Here we show the experimental implementation of a 1-2 random oblivious transfer (ROT) protocol by performing measurements on polarization-entangled photon pairs in a modified entangled quantum key distribution system, followed by all of the necessary classical post-processing including one-way error correction. We successfully exchange a 1,366 bits ROT string in ∼3 min and include a full security analysis under the noisy storage model, accounting for all experimental error rates and finite size effects. This demonstrates the feasibility of using today's quantum technologies to implement secure two-party protocols.Cryptography, prior to the modern computing age, was synonymous with the protection of private communications using a variety of encryption techniques, such as a wax seal or substitution cypher. However, with the advent of modern digital computing and an increasingly internet-driven society, important new cryptographic challenges have arisen. People now wish to do business and interact with others they neither know nor trust. In the field of cryptography this is known as secure two-party computation. Here we have two users, Alice and Bob, who wish to perform a computation on their private inputs in such a way that they obtain the correct output but without revealing any additional information about their inputs.A particularly important and familiar example is the task of secure identification, which we perform any time we use a bank's ATM to withdraw money. Here honest Alice (the bank) and honest Bob (the legitimate customer) share a password. When authenticating a new session, Alice checks to make sure she is really interacting with Bob by validating his password before dispensing any money. However, we do not want Bob to simply announce his password since a malicious Alice could steal his password and impersonate him in the future. What we require is a method for checking whether Bob's password is valid without revealing any additional information. While protocols for general two-party cryptographic tasks such as this one may be very involved, it is known that they can be built from a basic cryptographic building block called oblivious transfer (OT) [1].Many classical cryptography techniques currently in use have their security based on conjectured mathematical assumptions such as the hardness of finding the prime factors of a large number, assumptions which no longer hold once a sufficiently large quantum computer is built [2]. Alternatively, quantum cryptography offers means to accomplish cryptographic tasks which are provably secure using fewer assumptions that are ideally much more stringent than those employed classically. However, until now almost all of the experimental work has focused exclusively on q...

Experimental plug and play quantum coin flipping

“…However, although in principle the cheating probability bound in this protocol is independent of losses, a gain was shown in practice for a distance of a few metres. The closely related primitives of quantum bit commitment and oblivious transfer were experimentally demonstrated in the noisy storage model, where adversaries have access to an imperfect quantum memory 26,27 ; however, these protocols do not offer security against all-powerful adversaries. Finally, quantum bit commitment with relativistic constraints was also recently implemented 28,29 .…”

Modified E91 protocol demonstration with hybrid entanglement photon source

“…It enables us to implement various protocols such as bit commitment or oblivious transfer on the optical fiber. Those protocols provide features different from the QKD function, and proof of principle demonstrations have been carried out with polarization qubit [33,34]. Our hybrid entanglement photon source can integrate the advantages of polarization and time-bin qubits and implement such protocols with one-to-many service system easily.…”

A brief review on quantum bit commitment

“…8,34 Since the discovery of Mayers in 1997, efforts on bit commitment were put in combining quantum theory with relativity and in theoretical analysis and experimental realizations of practical protocols with noisy/bounded memories. 6,32,[35][36][37][38] It was shown that if the memory is not ideal but has a finite noise, there are protocols whose security will not be compromised as long as the time difference between the commitment and the opening phase is bigger than some threshold value, determined by the noisy characteristics of the memory used. 25 Regarding protocols based on relativistic effects, Kent has been working in this topic for several years, proposing several protocols for unconditionally secure bit commitment.…”