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EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Chapter 8, Problem P2P
Program Plan Intro
Known-Plaintext attack:
The Known-Plaintext attack is an attack model where the attacker has an access to the cipher text and its corresponding plaintext.
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Note: The notation from this problem is from Understanding Cryptography by Paar and Pelzl.
We conduct a known-plaintext attack against an LFSR. Through trial and error we have determined that the number of states is m = 4.
The plaintext given by
01001000 = rgx1L2X3X4X5X6X7
when encrypted by the LFSR produced the ciphertext
10000011 = Y0Y1Y2Y3Y3Y5Y6Y7-
What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 0101 to represent p3 = 0, p2 = 1, P1 = 0, Po = 1).
Suppose we have an alphabet of 30 characters, labelled as the integers modulo 30.
Suppose that a 2 × 2 affine shift cipher is used to encode a message and it is known
that the translation vector B is (0,0). The cipher text comes along as "21, 2, 13, 3,
14, 7, 0, 15,..." and you figure out through some other means that the plaintext starts
"15, 16, 1, 1,
plaintext?
." What is the encryption key? What are the next four digits of the
....
In a special case of a permutation cipher, we take a message, M, and write its letters in an s× t table, in a row-major fashion, and then let the ciphertext be a column-major listing of the entries in the table. For example, to encrypt the message ATTACKATDAWN, using a 3 × 4 table, we would write the message as ATTA CKAT DAWN and then write down the ciphertext as ACDTKATAWATN. The secret key in this cryptosystem is the pair (s, t). How is decryption done in this cryptosystem? Also, how hard would it be to attack this cryptosystem using a ciphertext-only attack?
Chapter 8 Solutions
EBK COMPUTER NETWORKING
Ch. 8 - Prob. R1RQCh. 8 - Prob. R2RQCh. 8 - Prob. R3RQCh. 8 - Prob. R4RQCh. 8 - Prob. R5RQCh. 8 - Prob. R6RQCh. 8 - Prob. R7RQCh. 8 - Prob. R8RQCh. 8 - Prob. R9RQCh. 8 - Prob. R10RQ
Ch. 8 - Prob. R11RQCh. 8 - Prob. R12RQCh. 8 - Prob. R13RQCh. 8 - Prob. R14RQCh. 8 - Prob. R15RQCh. 8 - Prob. R16RQCh. 8 - Prob. R17RQCh. 8 - Prob. R18RQCh. 8 - Prob. R19RQCh. 8 - Prob. R20RQCh. 8 - Prob. R21RQCh. 8 - Prob. R22RQCh. 8 - Prob. R23RQCh. 8 - Prob. R24RQCh. 8 - Prob. R25RQCh. 8 - Prob. R26RQCh. 8 - Prob. R27RQCh. 8 - Prob. R28RQCh. 8 - Prob. R29RQCh. 8 - Prob. R30RQCh. 8 - Prob. R31RQCh. 8 - Prob. R32RQCh. 8 - Prob. R33RQCh. 8 - Prob. P1PCh. 8 - Prob. P2PCh. 8 - Prob. P3PCh. 8 - Prob. P4PCh. 8 - Prob. P5PCh. 8 - Prob. P6PCh. 8 - Prob. P8PCh. 8 - Prob. P12PCh. 8 - Prob. P13PCh. 8 - Prob. P14PCh. 8 - Prob. P18PCh. 8 - Prob. P20PCh. 8 - Prob. P21PCh. 8 - Prob. P22PCh. 8 - Prob. P23P
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