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

The new left most bit is computed as a function of

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Unformatted text preview: ing is indeed random, this method encrypts M with a one-time pad and then encrypts both the pad and the encrypted message with each of the two algorithms. Since both are required to reconstruct M, a cryptanalyst must break both algorithms. The drawback is that the ciphertext is twice the size of the plaintext. This method can be extended to multiple algorithms, but the ciphertext expands with each additional algorithm. It’s a good idea, but I don’t think it’s very practical. 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 ----------- Chapter 16 Pseudo-Random-Sequence Generators and Stream Ciphers 16.1 Linear Congruential Generators Linear congruential generators are pseudo-random-sequence generators of the form Xn = (aXn-1 + b) mod m in which Xn is the nth number of the sequence, and Xn-1 is the previous number of the sequence. The variables a, b, and m are constants: a is the multiplier, b is the increment, and m is the modulus. The key, or seed, is the value of X0. This generator has a period no greater than m. If a, b, and m are properly chosen, then the generator will be a maximal period generator (sometimes called maximal length) and have period of m. (For example, b should be relatively prime to m.) Details on choosing constants to ensure maximal period can be found in [863,942]. Another good article on linear congruential generators and their theory is [1446]. Table 16.1, taken from [1272], gives...
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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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