Unformatted text preview: nction hashes the message in blocks of 64 bits and produces a 64bit hash value (See Figure 18.10). No known attack on this scheme is easier than brute force. Figure 18.10 Modified DaviesMeyer. PreneelBosselaersGovaertsVandewalle
This hash function, first proposed in [1266], produces a hash value twice the block length of the encryption algorithm: A 64bit algorithm produces a 128bit hash. With a 64bit block algorithm, the scheme produces two 64bit hash values, Gi and Hi, which are concatenated to produce the 128bit hash. With most block algorithms, the block size is 64 bits. Two adjacent message blocks, Li and Ri, each the size of the block length, are hashed together. G0 = IG, where IG is a random initial value H0 = IH, where IH is another random initial value Gi = ELi• Hi 1(Ri • Gi 1 ) • Ri • Gi 1 • Hi 1 Hi = ELi• Ri(Hi 1 • Gi 1 ) • Li • Gi 1 • Hi 1 Lai demonstrates attacks against this scheme that, in some instances, make the birthday attack trivially solvable [925, 926]. Preneel [1262] and Coppersmith [372] also have successful attacks against this scheme. Do not use it. QuisquaterGirault
This scheme, first proposed in [1279], generates a hash that is twice the block length and has a hash rate of 1. It has two hash values, Gi and Hi, and two blocks, Li and Ri, are hashed together. G0 = IG, where IG is a random initial value H0 = IH, where IH is another random initial value Wi = ELi(Gi  1 • Ri) • Ri • Hi 1 Gi = ERi(Wi • Li) • Gi 1 • Hi 1 • Li Hi = Wi • Gi 1 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 © 19962000 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...
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