Unformatted text preview: mputing power he has. Maurer claims that this scheme would be practical with about 100 different sequences of 1020 random bits each. Digitizing the face of the moon might be one way to get this many bits. 17.11 Cascading Multiple Stream Ciphers
If performance is no issue, there’s no reason not to choose multiple stream ciphers and cascade them. Simply XOR the output of each generator with the plaintext to get the ciphertext. Ueli Maurer’s result (see Section 15.7) says that if the generators have independent keys, then the security of the cascade is at least as secure as the strongest algorithm in the cascade. It is probably much more secure than that. Stream ciphers can be combined in all the same ways as block ciphers (see Chapter 15). Stream ciphers can be cascaded (see Section 15.7) with other stream ciphers, or together with block ciphers. 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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----------- A clever trick is to use one algorithm, either a block or stream algorithm, to frequently rekey a fast stream algorithm (which could even be a block algorithm in OFB mode). The fast algorithm could be weak, since a cryptanalyst would never see very much plaintext encrypted with any one key. There’s a trade-off between the size of the fast algorithm’s internal state (which may impact security) and how often you can afford to rekey. The rekey nee...
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