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

Computers are deterministic beasts stuff goes in one

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Unformatted text preview: 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) 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 ----------- Random-number generators are not random because they don’t have to be. Most simple applications, like computer games, need so few random numbers that they hardly notice. However, cryptography is extremely sensitive to the properties of random-number generators. Use a poor random-number generator and you start getting weird correlations and strange results [1231,1238]. If you are depending on your random-number generator for security, weird correlations and strange results are the last things you want. The problem is that a random-number generator doesn’t produce a random sequence. It probably doesn’t produce anything that looks even remotely like a random sequence. Of course, it is impossible to produce something truly random on a computer. Donald Knuth quotes John von Neumann as saying: “Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin” [863]. Computers are deterministic beasts: Stuff goes in one end, completely predictable operations occur inside, and different stuff comes out the other end. Put the same stuff in on two separate occasions and the same stuff comes out both times. Put the same stuff into two identical computers, and the same stuff comes out of both of them. A computer can only be in a finite number of states (a large finite number, but a finite number nonetheless), and the stuff that comes out will always be a deterministic function of the stuff that went in and t...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.

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