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arXiv:quant-ph/0502030 · IEEE International Symposium on Information Theory (ISIT)

Oblivious transfer and quantum non-locality

Stefan Wolf, Jürg Wullschleger

Published Jan 1, 2005• 32 citations
arXivHTMLPDF

Abstract

Oblivious transfer, a central functionality in modern cryptography, allows a party to send two one-bit messages to another who can choose one of them to read, remaining ignorant about the other, whereas the sender does not learn the receiver's choice. Oblivious transfer the security of which is information-theoretic for both parties is known impossible to achieve from scratch. The joint behavior of certain bi-partite quantum states is non-local, i.e., cannot be explained by shared classical information. In order to better understand such behavior, which is classically explainable only by communication, but does not allow for it, Popescu and Rohrlich have described a "non-locality machine": Two parties both input a bit, and both get a random output bit the XOR of which is the AND of the input bits. We show a close connection, in a cryptographic sense, between OT and the "PR primitive." More specifically, unconditional OT can be achieved from a single realization of PR, and vice versa. Our reductions, which are single-copy, information-theoretic, and perfect, also lead to a simple and optimal protocol allowing for inverting the direction of OT

DOI
10.1109/isit.2005.1523644

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Abstract- Oblivious transfer (OT) is an important primitive in cryptography. In chosen one-out-of-two OT, Alice offers two bits, one of which Bob can choose to read, not learning any information about the other bit. Alice on the other hand does not obtain any information about Bob’s choice. We present a new technique for the same task in quantum environment, based on POVM measurements. It is shown that our method has two important advantages over the previous approaches. First, it is unconditionally secure without invoking a commitment scheme, and second, it is more efficient in terms of communication complexity. Key words: Oblivious transfer, POVM measurements, Unconditional security

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Oblivious transfer, a central functionality in modern cryptography, allows a party to send two one-bit messages to another who can choose one of them to read, remaining ignorant about the other, whereas the sender does not learn the receiver's choice. Oblivious transfer the security of which is information-theoretic for both parties is known impossible to achieve from scratch. The joint behavior of certain bi-partite quantum states is non-local, i.e., cannot be explained by shared classical information. In order to better understand such behavior, which is classically explainable only by communication, but does not allow for it, Popescu and Rohrlich have described a "non-locality machine": Two parties both input a bit, and both get a random output bit the XOR of which is the AND of the input bits. We show a close connection, in a cryptographic sense, between OT and the "PR primitive." More specifically, unconditional OT can be achieved from a single realization of PR, and vice versa. Our reductions, which are single-copy, information-theoretic, and perfect, also lead to a simple and optimal protocol allowing for inverting the direction of OT
Oblivious transfer (OT) is an important tool in cryptography. It serves as a subroutine to other complex procedures of both theoretical and practical significance. A common attribute of OT protocols is that one party (Alice) has to send a message to another party (Bob) and has to stay oblivious to whether Bob did receive the message. Specific (OT) protocols vary by exact definition of the task---in the all-or-nothing protocol, Alice sends a single bit-string message, which Bob is able to read with only 5050%50 probability, whereas in a 1-out-of-2 OT protocol Bob reads one out of two messages sent by Alice. These two flavors of protocol are known to be equivalent. Recently, a computationally secure all-or-nothing OT protocol based on quantum states was developed by A. Souto et al. [Phys. Rev. A 91, 042306 (2015)], which, however, cannot be reduced to a 1-out-of-2 OT protocol by standard means. Here we present an elaborate reduction of this protocol that retains the security of the original.
Oblivious transfer (OT) is an important cryptographic primitive.Any multiparty computation can be realized with OT as building block.XOR oblivious transfer (XOT) is a variant where the sender Alice has two bits and a receiver Bob obtains either the first bit, the second bit, or their XOR.Bob should not learn anything more than this and Alice should not learn what Bob has learnt.Perfect quantum OT with information-theoretic security is known to be impossible.We determine the smallest possible cheating probabilities for unrestricted dishonest parties in noninteractive quantum XOT protocols using symmetric pure states and present an optimal protocol, which outperforms classical protocols.We also "reverse" this protocol, so that Bob becomes sender of a quantum state and Alice the receiver who measures it, while still implementing oblivious transfer from Alice to Bob.Cheating probabilities for both parties stay the same as for the unreversed protocol.We optically implement both the unreversed and the reversed protocols, and cheating strategies, noting that the reversed protocol is easier to implement.
Oblivious transfer (OT) is a fundamental cryptographic primitive that is useful for realizing any two-party computation. Since information-theoretically secure perfect OT is impossible classically and quantumly, research has focused on imperfect protocols, exploring how close to perfect one can get against unbounded dishonest parties. While current approaches often make use of pure quantum states, recent work suggests that mixed quantum states may improve performance. In this paper, we investigate the use of mixed quantum states in Rabin oblivious transfer, where a sender holds one bit and a receiver learns its value with a certain probability while the sender remains ignorant of whether the receiver learned it. We present three mixed-state protocols constructed with two distinct methods, extending an existing pure-state scheme and employing a probabilistic approach, and demonstrate improved performance compared to classical and quantum pure-state protocols across varying parameters.
Oblivious transfer is a fundamental cryptographic primitive that is useful for secure multiparty computation. There are several variants of oblivious transfer. We consider 1-out-of-2 oblivious transfer, where a sender sends two bits of information to a receiver. The receiver receives only one of the two bits, while the sender does not know which bit the receiver has received. Perfect quantum oblivious transfer with information-theoretic security is known to be impossible. We aim to find the lowest possible cheating probabilities. Bounds on cheating probabilities have been investigated for “complete” protocols, where if both parties follow the protocol, the bit value obtained by the receiver matches the sender's bit value. We instead investigate incomplete protocols, where the receiver obtains an incorrect bit value with probability p f . We present optimal noninteractive protocols where Alice's bit values are encoded in four symmetric pure quantum states, and where she cannot cheat better than with a random guess. We find the protocols such that for a given p f , Bob's cheating probability p r is as low as possible, and vice versa. Furthermore, we show that noninteractive quantum protocols can outperform noninteractive classical protocols and give a lower bound on Bob's cheating probability in interactive quantum protocols. Importantly for optical implementations, our protocols do not require entanglement nor quantum memory.
We propose a quantum protocol for 1-out-of-2, 1-out-of-n and k-out-of-n oblivious transfer. Oblivious transfer is a counter-intuitive cryptographic primitive in which the receiver receives only the information he is authorized for, while the sender does not know what information receiver received. In 1-out-of-2 oblivious transfer, Alice sends two bits to Bob who can choose only one of them to read, while Alice does not know which bit Bob read. k-out-of-n oblivious transfer is an extension of this idea. The proposed protocols do not require any classical communication, are practical, secure and can be implemented using current technology.
Abstract- Oblivious transfer (OT) is an important primitive in cryptography. In chosen one-out-of-two OT, Alice offers two bits, one of which Bob can choose to read, not learning any information about the other bit. Alice on the other hand does not obtain any information about Bob’s choice. We present a new technique for the same task in quantum environment, based on POVM measurements. It is shown that our method has two important advantages over the previous approaches. First, it is unconditionally secure without invoking a commitment scheme, and second, it is more efficient in terms of communication complexity. Key words: Oblivious transfer, POVM measurements, Unconditional security