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

Alice just generates a new x and the protocol

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Unformatted text preview: gh the protocol herself. Of course, if she were watching over Bob’s shoulder as he completed the protocol, she would be convinced. Carol has to see the steps done in order, just as Bob does. There may be a problem with this signature scheme, but I know of no details. Please pay attention to the literature before you use it. Another protocol not only has a confirmation protocol—Alice can convince Bob that her signature is valid—but it also has a disavowal protocol; Alice can use a zero-knowledge interactive protocol to convince him that the signature is not valid, if it is not [329]. 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 ----------- Like the previous protocol, a group of signers use a shared public large prime, p, and a primitive element, g. Alice has a unique private key, x, and a public key, gx mod p. To sign a message, Alice computes z =mx mod p. To verify a signature: (1) Bob chooses two random numbers, a and b, both less than p, and sends Alice: c = magb mod p (2) Alice chooses a random number, q, less than p, and computes and sends to Bob: s1 = cgq mod p, s2 = (cgq)x mod p (3) Bob sends Alice a and b, so that Alice can confirm that Bob did not cheat in step (1). (4) Alice sends Bob q, so that Bob can use mx and reconstruct s1 and s2. If then the signature is valid. s1 a cgq (mod p) s2 a (gx)b +qza (mod...
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