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Introduction to Cryptography with Coding Theory, 3rd Edition
book

Introduction to Cryptography with Coding Theory, 3rd Edition

by Wade Trappe, Lawrence C. Washington
February 2020
Beginner
621 pages
19h 34m
English
Pearson
Content preview from Introduction to Cryptography with Coding Theory, 3rd Edition

C.2 Examples for Chapter 2

Example 1

A shift cipher was used to obtain the ciphertext kddkmu.

Decrypt it by trying all possibilities.

>> allshift(’kddkmu’)


kddkmu
leelnv
mffmow
nggnpx
ohhoqy
piiprz
qjjqsa
rkkrtb
sllsuc
tmmtvd
unnuwe
voovxf
wppwyg
xqqxzh
yrryai
zsszbj
attack
buubdl
cvvcem
dwwdfn
exxego
fyyfhp
gzzgiq
haahjr
ibbiks
jccjlt

As you can see, attack is the only word that occurs on this list, so that was the plaintext.

Example 2

Encrypt the plaintext message cleopatra using the affine function 7x+8:

>> affinecrypt(’cleopatra’,7,8)

ans =


’whkcjilxi’

Example 3

The ciphertext mzdvezc was encrypted using the affine function 5x+12. Decrypt it.

SOLUTION

First, solve y5x+12(mod26) for x to obtain x51(y12). We need to find the ...

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Publisher Resources

ISBN: 9780136758181