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Unformatted text preview: encrypted messages over a channel that sometimes drops messages. With a pseudorandom function family, you can encrypt under k the nth message you transmit, xn, as n together with the XOR of xn and k(n). The receiver doesn’t need to store any state to recover xn, nor does he need to worry about lost messages affecting the message decryption process. Description of SEAL
The inner loop of SEAL is shown by Figure 17.1. Three keyderived tables, called R, S, and T, drive the algorithm. The preprocessing step maps the key k, to these tables using a procedure based on SHA (see Section 18.7). The 2kilobyte table, T, is a 9 * 32 bit Sbox. 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 © 19962000 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)
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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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 SEAL also uses four 32bit registers, A, B, C, and D, whose initial values are determined by n and the kderived tables R and T. These registers get modified over several iterations, each one involving 8 rounds. In each round 9 bits of a first register (either A, B, C, or D) are used to index into table T. The value retrieved from T is then added to or XORed with the contents of a second register: again one of A, B, C, or D. The first register is then circularly shifted by nine positions. In some rounds the second register is further modified by adding or XORing it with the (now shifted) first register. After 8 rounds of this, A, B, C, and D are added to the keystream, each masked first by adding or XORing it with a certain word from S. The iteration is completed by adding to A...
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 Fall '10
 ALIULGER
 Cryptography

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