An oblivious transfer (OT) channel takes as input a pair of bits (s0, s1) from the sender and delivers (c, sc) to the receiver, where c ∈ {0, 1} is chosen uniformly at random. A secure implementation of such a channel hides c from the sender and s1-cfrom the receiver. These secrecy properties make OT channels very useful for cryptography; for example, they can be used to perform general secure multi-party computation.
An oblivious transfer (OT) channel takes as input a pair of bits (s0, s1) from the sender and delivers (c, sc) to the receiver, where c ∈ {0, 1} is chosen uniformly at random. A secure implementation of such a channel hides c from the sender and s1-cfrom the receiver. These secrecy properties make OT channels very useful for cryptography; for example, they can be used to perform general secure multi-party computation.
1 IntroductionOblivious Transfer (OT) protocols allow one party, the sender, to transmit part of its inputs to another party, the chooser, in a manner that protects both of them: the sender is assured that the chooser does not receive more information than it is entitled, while the chooser is assured that the sender does not learn which part of the inputs it received. OT is used as a key component in many applications of cryptography. Its computational requirements are quite demanding and they are likely to be the bottleneck in many applications that invoke it.1.1 Contributions.This paper presents several significant improvements to oblivious transfer (OT) protocols of strings, and in particular: (i) Improving the efficiency of applications which many invocations of oblivious transfer. (ii) Providing the first two-round OT protocol whose security analysis does not invoke the random oracle model.
Oblivious transfer (OT) protocol is an essential tool in cryptography that provides a wide range of applications such as secure multi-party computation, private information retrieval, private set intersection, contract signing, and privacy-preserving location-based services. The OT protocol has different variants such as one-out-of-2, one-out-of- n , k -out-of- n , and OT extension. In the OT (one-out-of-2, one-out-of- n , and OT extension) protocol, the sender has a set of messages, whereas the receiver has a key. The receiver sends that key to the sender in a secure way; the sender cannot get any information about the received key. The sender encrypts every message by operating on every message using the received key and sends all the encrypted messages to the receiver. The receiver is able to extract only the required message using his key. However, in the k -out-of- n OT protocol, the receiver sends a set of k keys to the sender, and in replay, the sender sends all the encrypted messages. The receiver uses his keys and extracts the required messages, but it cannot gain any information about the messages that it has not requested. Generally, the OT protocol requires high communication and computation cost if we transfer millions of oblivious messages. The OT extension protocol provides a solution for this, where the receiver transfers a set of keys to the sender by executing a few numbers of OT protocols. Then, the sender encrypts all the messages using cheap symmetric key cryptography with the help of a received set of keys and transfers millions of oblivious messages to the receiver. In this work, we present different variants of OT protocols such as one-out-of-2, one-out-of- n , k -out-of- n , and OT extension. Furthermore, we cover various aspects of theoretical security guarantees such as semi-honest and malicious adversaries, universally composable, used techniques, computation, and communication efficiency aspects. From the analysis, we found that the semi-honest adversary-based OT protocols required low communication and computation costs as compared to malicious adversary-based OT protocols.
Oblivious transfer (OT) protocol is a fundamental building block of cryptography and can be applied widely in many fields. A secure oblivious transfer protocol is supposed to ensure the privacy of both senders and receivers. The privacy of receivers means that the information being selected by receivers would never be revealed to senders. On the other hand, the privacy of senders means that receivers have no further information except for the one that has been selected. In this case, senders are able to deceive receivers by sending same messages. Likewise, in existing 1-out-of-n OT protocols, malicious senders can make all the n messages the same, so that receivers will always get the specific one assigned by senders. This indicates that privacy of receivers wouldnt work under the 1-out-of-n OT protocol. To prevent this kind of attack, this paper provides a general framework on how to design a secure OT protocol based on commutative and ciphertext equality test and take RSA as an example to explain how the protocol is processed.
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
Abstract Oblivious Transfer ( OT OT ) is a fundamental cryptographic primitive that becomes a crucial component of a practical secure protocol. OT OT is typically implemented in software, and one way to accelerate its running time is by using hardware implementations. However, such implementations are vulnerable to side-channel attacks (SCAs). On the other hand, protecting interactive protocols against SCA is highly challenging due to their longer secrets (which include inputs and randomness), more complex design, and the need to run multiple instances. Consequently, there are no truly practical leakage-resistant OT OT protocols yet. In this paper, we introduce two tailored indistinguishability-based security definitions for leakage-resilient OT OT , focusing on protecting the sender’s state. Second, we propose a practical semi-honest secure OT OT protocol that achieves these security levels while minimizing the assumptions on the protocol’s building blocks and the use of a secret state.
The Oblivious Transfer (OT), introduced by Rabin in 1981, has become an important and fundamental cryptography technique. An OT protocol should have two important characteristics: sender's privacy and chooser's privacy. The sender is a party who will deliver a secret to chooser. The chooser is another party who acts as receiver to learn some information about input from sender. The chooser learns of certain information concerning sender's input while sender is not allowed to know what chooser has learned. Moreover, chooser cannot acquire any messages that he/she did not choose. Naor and Pinkas have recently proposed an efficient oblivious transfer protocol (EOT) that implementes 1-out-of-n protocol, but this EOT has a flaw: it cannot withstand the same message attack. In this paper, we will improve Naor and Pinkas EOT and make it resistant to the same message attack.