EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Chapter 8, Problem P3P
Program Plan Intro
Chosen-Plaintext attack:
A chosen-plaintext attack is an attack model where a cryptanalyst can choose arbitrary plaintext data to be encrypted and then he or she receives the corresponding cipher text.
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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).
Alice and Bob are using the ElGamal cipher with
the parameters p = 199 and a = 3.
Their parameters are small and we decide to crack the
cipher.
Suppose Alice is observed sending public ephemeral
key k = 103 and Bob sends public key = 136.
ß
Alice is observed transmitting the ciphertext y = 68.
a) What is the masking key km?
b) What is the plaintext?
Alice and Bob are using the EIGamal cipher with
the parameters p = 89 and a = 3.
Suppose Alice is observed sending public ephemeral
key KE 7 and Bob sends public key ß = 44.
=
Their private keys are i = 81 and d = 28, respectively.
a) What is the masking key k?
b) What is the encryption of x = 31?
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
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