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

Its very similar in concept to using salt when

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Unformatted text preview: t be stored securely. 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 ----------- Key Distribution in Large Networks Key-encryption keys shared by pairs of users work well in small networks, but can quickly get cumbersome if the networks become large. Since every pair of users must exchange keys, the total number of key exchanges required in an n-person network is n(n – 1)/2. In a six-person network, 15 key exchanges are required. In a 1000-person network, nearly 500,000 key exchanges are required. In these cases, creating a central key server (or servers) makes the operation much more efficient. Alternatively, any of the symmetric-cryptography or public-key-cryptography protocols in Section 3.1 provides for secure key distribution. Figure 8.2 Key distribution via parallel channels. 8.4 Verifying Keys When Bob receives a key, how does he know it came from Alice and not from someone pretending to be Alice? If Alice gives it to him when they are face-to-face, it’s easy. If Alice sends her key via a trusted courier, then Bob has to trust the courier. If the key is encrypted with a key-encryption key, then Bob has to trust the fact that only Alice has that key. If Alice uses a digital signature protocol to sign the key, Bob has to trust the public-key database when he verifies that signature. (He also has to trust that Alice has kept her key secure.) If a Key Distribution Center...
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