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

Applied cryptography second edition protocols

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Unformatted text preview: 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 ----------- Another method is suggested in [352]. First, each listener shares a secret key with Alice, one that is larger than any possible encrypted message. All of those keys should be pairwise prime. She encrypts the message in a random key, K. Then, she computes a single integer, R, such that R modulo a secret key is congruent to K when that secret key is supposed to decrypt the message, and R modulo a secret key is otherwise congruent to zero. For example, if Alice wants the secret to be received by Bob, Carol, and Ellen, but not by Dave and Frank, she encrypts the message with K and then computes R such that Ra K(mod KB) Ra K(mod KC) Ra 0 (mod KD) Ra K(mod KE) Ra 0 (mod KF) This is a straightforward algebra problem, one that Alice can solve easily. When listeners receive the broadcast, they compute the received key modulo their secret key. If they were intended to receive the message, they recover the key. Otherwise, they recover nothing. Yet a third way, using a threshold scheme (see Section 3.7), is suggested in [141]. Like the others, every potential receiver gets a secret key. This key is a shadow in a yet-uncreated threshold scheme. Alice saves some secret keys for herself, adding some randomness to the system. Let’s say there are k people out there. Then, to broadcast M, Alice encrypts M with key K and does the following. (1) Alice chooses a random number, j. This number serves to hide the number of recipients of the message. It doesn’t have to...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.

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