Unformatted text preview: sage to Alice. (5) Alice sends the other half of her encrypted message to Bob. (6) Bob puts the two halves of Alice’s message together and decrypts it with his private key. Bob sends the other half of his encrypted message to Alice. (7) Alice puts the two halves of Bob’s message together and decrypts it with her private key. The important point is that half of the message is useless without the other half; it can’t be decrypted. Bob cannot read any part of Alice’s message until step (6); Alice cannot read any part of Bob’s message until step (7). There are a number of ways to do this: — If the encryption algorithm is a block algorithm, half of each block (e.g., every other bit) could be sent in each half message. — Decryption of the message could be dependent on an initialization vector (see Section 9.3), which could be sent with the second half of the message. — The first half of the message could be a one-way hash function of the encrypted message (see Section 2.4) and the encrypted message itself could be the second half. 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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----------- To see how this causes a problem for Mallory, let’s review his attempt to subvert the protocol. He can still substitute his own public keys for Alice’s and Bob’s in steps (1) and (2). But now, when he inte...
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