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

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Unformatted text preview: key, and you have a secure digital signature. In other cases—DSA is an example (see Section 20.1)—there is a separate algorithm for digital signatures that cannot be used for encryption. This idea was first invented by Diffie and Hellman [496] and further expanded and elaborated on in other texts [1282,1328,1024,1283,426]. See [1099] for a good survey of the field. The basic protocol is simple: (1) Alice encrypts the document with her private key, thereby signing the document. (2) Alice sends the signed document to Bob. (3) Bob decrypts the document with Alice’s public key, thereby verifying the signature. This protocol is far better than the previous one. Trent is not needed to either sign or verify signatures. (He is needed to certify that Alice’s public key is indeed her public key.) The parties do not even need Trent to resolve disputes: If Bob cannot perform step (3), then he knows the signature is not valid. 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 ----------- This protocol also satisfies the characteristics we’re looking for: 1. The signature is authentic; when Bob verifies the message with Alice’s public key, he knows that she signed it. 2. The signature is unforgeable; only Alice knows her private key. 3. The signature is not reusable; the signature is a function of the document and cannot be transferred to any other document. 4. The signed document is unalterable; if ther...
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