applied cryptography - protocols, algorithms, and source code in c

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Unformatted text preview: heir secret. More details are in [1374,1175]. Previous Table of Contents Next Products | Contact Us | About Us | Privacy | Ad Info | Home Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc. All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement. To access the contents, click the chapter and section titles. Applied Cryptography, Second Edition: Protocols, Algorthms, and Source Code in C (cloth) Go! Keyword Brief Full Advanced Search Search Tips (Publisher: John Wiley & Sons, Inc.) Author(s): Bruce Schneier ISBN: 0471128457 Publication Date: 01/01/96 Search this book: Go! Previous Table of Contents Next ----------- Unfortunately, a pair of dishonest parties can cheat. Alice and Carol, working together, can easily find out what secret Bob is getting: If they know the FBI of Cb and Bob’s encryption algorithm, they can find b such that Cb has the right FBI. And Bob and Carol, working together, can easily get all the secrets from Alice. If you assume honest parties,there’s an easier protocol [389]. (1) Alice encrypts all of the secrets with RSA and sends them to Bob: Ci = Sie mod n (2) Bob chooses his secret Cb, picks a random r, and sends C', to Alice. C' = Cbre mod n (3) Alice sends Bob P'. P' = C'd mod n (4) Bob calculates Sb. Sb = P'r-1 mod n If the parties may be dishonest, Bob can prove in zero-knowledge that he knows some r such that C'=Cbre mod n and keep b secret until Alice gives him P' in step (3) [246]. 23.10 Fair and Failsafe Cryptosystems Fair Diffie-Hellman Fair cryptosystems are a way to do key escrowing in software (see Section 4.14). This example is from Silvio Micali [1084,1085]. It is patented [1086,1087]. In the basic Diffie-Hellman scheme, a group of users share a prime, p, and a generator, g. Alice’s private key is s, and her public key is t =gs mod p. Here’s how to make Diffie-Hellman fair (this example uses five tr...
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