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

O box 1600 stamford ct 06904 1600 138 rc2 rc2 is a

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: o produce the ciphertext. The subkeys are generated from the key in a straightforward manner. The 64-bit key is split into a left half and a right half. In each round, the subkey is the left half. This left half is then rotated 12 or 13 bits to the left, and then every two rounds the left and right halves are exchanged. As with DES, the same algorithm can be used for both encryption and decryption, with some modification in how the subkeys are used. Table 13.1 Expansion Permutation 4, 28, 20, 12, 3, 27, 19, 11, 2, 26, 18, 10, 1, 25, 17, 9, 32, 24, 16, 8, 31, 23, 15, 7, 20, 22, 14, 6, 29, 21, 13, 5, 28, 20, 12, 4, 27, 19, 11, 3, 26, 18, 10, 2, 25, 17, 9, 1 Table 13.2 Pr r: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 Pr: 375, 379, 391, 395, 397, 415, 419, 425, 433, 445, 451, 463, 471, 477, 487, 499 Cryptanalysis of LOKI91 Knudsen attempted to cryptanalyze LOKI91 [854, 858], but found it secure against differential cryptanalysis. However, he found a related-key chosen-plaintext attack that reduces the complexity of a brute-force search by almost a factor of four. This attack exploits a weakness in the key schedule and may also apply if the algorithm is used as a one-way hash function (see Section 18.11). Another attack on related keys can break LOKI91 with 232 chosen-key chosen plaintexts, or 248 chosen-key known plaintexts [158]. The attack is independent of the number of rounds of the algorithm. (In the same paper, Biham breaks LOKI89 with 217 chosen-key chosen plaintexts or 233 known-key known plaintexts using related-key cryptanalysis.) It’s easy to make LOKI91 resistant to this attack; avoid the simple key schedule. 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 pr...
View Full Document

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.

Ask a homework question - tutors are online