Unformatted text preview: rators. For example: Ai = (Ai-55 + Ai-24) mod 232 Bi = (Bi-57 + Bi-7) mod 232 Ci = (Ci-58 + Ci-19) mod 232 To generate the keystream word, look at the addition carry bits. If all three agree (all are 0 or all are 1), then clock all three generators. If they do not, just clock the two generators that agree. Save the carry bits for next time. The final output is the XOR of the three generators. Pike is faster than Fish, since on the average 2.75 steps will be required per output rather than 3. It is far too new to trust, but looks good so far. Mush
Mush is a mutual shrinking generator. It’s easy to explain . Take two additive generators: A and B. If the carry bit of A is set, clock B. If the carry bit of B is set, clock A. Clock A, and set the carry bit if there is a carry. Clock B, and set the carry bit if there is a carry. The final output is the XOR of the output of A and B. The easiest generators to use are the ones from Fish: Ai = (Ai-55 + Ai-24) mod 232 Bi = (Bi-52 + Bi-19) mod 232 On the average, three generator iterations are required to produce one output word. And if the coefficients of the additive generators are chosen correctly and are relatively prime, the output sequence will be maximal length. I know of no successful attacks, but remember that this algorithm is very new. 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)
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:
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