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

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Unformatted text preview: of no cryptanalysis of this mode. More Modes Other modes are possible, although they are not extensively used. Plaintext block chaining (PBC) is like CBC except the previous plaintext block is XORed with the plaintext block instead of with the ciphertext block. Plaintext feedback (PFB) is like CFB, except the plaintext, not the ciphertext, is used for feedback. These two modes allow chosen-plaintext attacks in order to resist known-plaintext attacks. There is also cipher block chaining of plaintext difference (CBCPD). I’m sure it gets even weirder. If a cryptanalyst has a brute-force keysearch machine, then he can recover the key if he can guess one of the plaintext blocks. Some of these stranger modes amount to light encryption before applying the encryption algorithm: for example, XORing the text with a fixed secret string or permuting the text. Almost anything nonstandard will frustrate this sort of cryptanalysis. 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. Table 9.1 Summary of Block Cipher Modes 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 ----------- 9.11 Choosing a Cipher Mode If simplicity and speed are your main concerns, ECB is the easiest and fastest mode to use a block cipher. It is also the weakest. Besides being vulnerable to replay attacks, an algorithm in ECB mode is the easiest to cryptanalyze. I don’t recommend ECB for message encryption. For encrypting random data, such as other keys, ECB is a g...
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