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

Alice knows a bob knows b and together they will

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Unformatted text preview: handle situations more complex than determining which of two numbers is greater. And two, if Alice and Bob were really concerned about the secrecy of their information, they would be forced to drown the waiter in a bowl of vichyssoise, lest he tell the wine steward. Public-key cryptography offers a far less violent solution. There is a protocol by which Alice, who knows a value a, and Bob, who knows a value b, can together determine if a < b, so that Alice gets no additional information about b and Bob gets no additional information about a. And, both Alice and Bob are convinced of the validity of the computation. Since the cryptographic algorithm used is an essential part of the protocol, details can be found in Section 23.14. 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) 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 ----------- Of course, this protocol doesn’t protect against active cheaters. There’s nothing to stop Alice (or Bob, for that matter) from lying about her age. If Bob were a computer program that blindly executed the protocol, Alice could learn his age (is the age of a computer program the length of time since it was written or the length of time since it started running?) by repeatedly executing the protocol. Alice might give her age as 60. After learning that she is older, she could execute the protocol again with her age as 30. After learning that Bob is older, she could execute the protocol again with her age as 45, and so on, until Alice discovers Bob’s age to any degree of accuracy she wishes. Assuming that the participants don’t actively cheat, it is easy to extend this protocol to multiple participants. Any n...
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