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A Note on the Bellare-Rivest Protocol for

Zhengjun Cao, Lihua Liu

Published Jan 1, 2014• 0 citations
OpenAlex

Abstract

AbstractWe remark that the Bellare-Rivest protocol for translucent cryptography [J. Cryptology(1999) 12: 117-139] can not truly enable the government to decrypt partial encrypted commu-nications.Keywords. Translucent cryptography, individual privacy, oblivious transfer, ElGamal en-cryption. 1 Introduction The primitive of translucent cryptography introduced by Bellare and Rivest [2] is viewed as analternative to the controversial key-escrow techniques. It aims to achieve an appropriate balancebetween individual privacy and government access to communications. The main idea behind theirprotocol for the primitive can be described as follows.Suppose that Bob’s public key is pk B and Larry’s public parameters are V 1 ,··· ,V t , where therole of Larry is played by the government. Among these V 1 ,··· ,V t , only one is the good parameterfor Larry, i.e., he knows the relevant trapdoor. But nobody knows which is the good parameterexcept Larry himself. When Alice wants to send a session key s to Bob, which shall be used forthe later symmetric encryption, she randomly picks a parameter V

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This work examines the part of an asymmetric cryptography called an oblivious transfer. Our goal is to bring a comprehensive overwiew about particular variants of an oblivious transfer and to describe construcions of these variants. A component of the work is an introduction of definitions needed for proving the security of protocols which implements the schemes. We are examining the security of protocols in a semi-honest model. There is informatively explained Rabin's oblivious transfer, but we mainly focused on so-called 1-2, 1-n and m-n alternatives of an oblivious transfer. We mention at least one scheme for each alternative, which we have proven that it is secured. Powered by TCPDF (www.tcpdf.org)

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AbstractWe remark that the Bellare-Rivest protocol for translucent cryptography [J. Cryptology(1999) 12: 117-139] can not truly enable the government to decrypt partial encrypted commu-nications.Keywords. Translucent cryptography, individual privacy, oblivious transfer, ElGamal en-cryption. 1 Introduction The primitive of translucent cryptography introduced by Bellare and Rivest [2] is viewed as analternative to the controversial key-escrow techniques. It aims to achieve an appropriate balancebetween individual privacy and government access to communications. The main idea behind theirprotocol for the primitive can be described as follows.Suppose that Bob’s public key is pk B and Larry’s public parameters are V 1 ,··· ,V t , where therole of Larry is played by the government. Among these V 1 ,··· ,V t , only one is the good parameterfor Larry, i.e., he knows the relevant trapdoor. But nobody knows which is the good parameterexcept Larry himself. When Alice wants to send a session key s to Bob, which shall be used forthe later symmetric encryption, she randomly picks a parameter V
In this paper we study the relationships among some of the most fundamental primitives and protocols in cryptography: public-key encryption (i.e. trapdoor predicates), oblivious transfer (which is equivalent to general secure multi-party computation), key agreement and trapdoor permutations. Our main results show that public-key encryption and oblivious transfer are incomparable under black-box reductions. These separations are tightly matched by our positive results where a restricted (strong) version of one primitive does imply the other primitive. We also show separations between oblivious transfer and key agreement. Finally, we conclude that neither oblivious transfer nor trapdoor predicates imply trapdoor permutations. Our techniques for showing negative results follow the oracle separations of R. Impagliazzo and S. Rudich (1989).
a cryptographic key, enabling Alice to scramble her messages in a way only Bob, knowing the same key, could unscramble. Privacy thus appeared to be generally unavailable to users lacking the means and foresight by which diplomats and spies share secret keys with their intended correspondents. Classical cryptography offered no purely mathematical solution to this "key distribution problem ". Meanwhile the only solution to the discreet communications problem appeared to be for Alice and Bob to confide their secrets in a trusted intermediary, who might later choose to blackmail them. All this was changed by PKC. The idea of PKC is for each user (eg Alice) to randomly choose a pair of mutually inverse transformations---a scrambling transformation and an unscrambling transformation---and to publish the directions for performing the former but not the latter. Anyone, including Bob, can then use Alice's public scrambling algorithm to prepare a message that only she can unscramble. Si
Abstract. The main purpose of this paper is to show that public key encryption can be secure against the “encryption emulation ” attack (on the sender’s encryption) by computationally unbounded adversary, with one reservation: a legitimate receiver decrypts correctly with probability that can be made arbitrarily close to 1, but not equal to 1. 1. Summary of our claims We thought it would make sense to summarize, for the reader’s convenience, our two main claims in a separate section, before proceeding to a narrative introduction. In Section 3, we describe a public-key encryption protocol that allows Bob (the sender) to send secret information to Alice (the receiver), encrypted one bit at a time, so that: (1) Assuming that Eve (the adversary): (a) is computationally unbounded, (b) knows everything about Bob’s encryption algorithm and hardware, (c) does not know Alice’s algorithm for creating public key, then: she cannot decrypt any single bit correctly with probability> 3 4
Oblivious transfer is an important primitive in modern cryptography and is widely utilized in designing more complex protocols. In a one-out-of-two oblivious transfer, a party Alice has two messages x0, x1send to another party Bob in such a way that he can decide to obtain one of them at his choice but not both. In the literature (A. Kawachi et al., EUROCRYPT 2005, 268-284), the quantum states ppi+and ppi-are used as public keys to construct an encryption algorithm. In the paper, we further demonstrate that, for pi ne thetas, the quantum states ppiplusmnand pthetasplusmncan't been distinguished by quantum computers. Using this result, we devise a one-out-of-two oblivious transfer scheme, in which any cheating of the entities are detected at the end of the protocol. Correctness and privacy of this protocol are analyzed and results show that the proposed scheme is computationally secured
This work examines the part of an asymmetric cryptography called an oblivious transfer. Our goal is to bring a comprehensive overwiew about particular variants of an oblivious transfer and to describe construcions of these variants. A component of the work is an introduction of definitions needed for proving the security of protocols which implements the schemes. We are examining the security of protocols in a semi-honest model. There is informatively explained Rabin's oblivious transfer, but we mainly focused on so-called 1-2, 1-n and m-n alternatives of an oblivious transfer. We mention at least one scheme for each alternative, which we have proven that it is secured. Powered by TCPDF (www.tcpdf.org)