Unformatted text preview: with higher-order differential cryptanalysis. Who knows? 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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----------- 12.5 The Real Design Criteria
After differential cryptanalysis became public, IBM published the design criteria for the S-boxes and the P-box [373,374]. The criteria for the S-boxes are: — Each S-box has 6 input bits and 4 output bits. (This was the largest size that could be accommodated in a single chip with 1974 technology.) — No output bit of an S-box should be too close to a linear function of the input bits. — If you fix the left-most and right-most bits of an S-box and vary the 4 middle bits, each possible 4-bit output is attained exactly once. — If two inputs to an S-box differ in exactly 1 bit, the outputs must differ in at least 2 bits. — If two inputs to an S-box differ in the 2 middle bits exactly, the outputs must differ in at least 2 bits. — If two inputs to an S-box differ in their first 2 bits and are identical in their last 2 bits, the two outputs must not be the same. — For any nonzero 6-bit difference between inputs, no more than 8 of the 32 pairs of inputs exhibiting that difference may result in the same output difference. — A criterion similar to the previous one, but for the case of three active S-boxes. The criteria for the P-box are: — The 4...
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