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.
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.
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) has been regarded as one of the most significant cryptography tools in recent decades.Since the mechanism of OT is widely used in many applications such as e-commerce, secret information exchange, and games, various OT schemes have been proposed to improve its functionality and efficiency.In 2001, Naor and Pinkas proposed a secure 1-out-of-n OT protocol, in which the sender has n messages and the chooser can get one of these n messages in each protocol run.What is more, the sender cannot find which message has been chosen by the chooser and the chooser knows only the correct message.In 2004, Wakaha and Ryota proposed a secure t-out-of-n OT protocol, which is an extension of the 1-out-of-n OT protocol proposed by Naor and Pinkas.Wakaha and Ryota's tout-of-n OT protocol allows the chooser to get t messages from the sender simultaneously in each protocol run.Besides, the sender cannot know what the chooser has chosen and the chooser can only know the exact t messages.However, getting deep understanding of Wakaha and Ryota's protocol, it could be concluded that it still lacks efficiency such that it is hard to be applied in real-world applications.In this article, a secure and efficient t-out-of-n OT protocol based on the Generalized Chinese Remainder Theorem is proposed, in which the chooser can securely get t messages from the sender simultaneously in each protocol run.The efficiency of the proposed t-out-of-n OT protocol is higher than that of Wakaha and Ryota's protocol in terms of practical application.
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 (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 protocol,which is an important and useful cryptographic protocol,has been widely applied in cryptographic field,especially in construction of secure multi-party computation protocol.However,all of present oblivious transfer protocols have two drawbacks for requirement of their secrets: ① the receiver does not know whether message received is one of the messages held by the sender;② the sender does not know whether message received by the receiver is one of the messages designated by himself.In order to conquer these drawbacks,we firstly introduce the notion of verifiable oblivious transfer protocol,and firstly construct it by using proof protocol of knowledge,i.e.,∑-protocol,as main tool.