Security in computing and information technology

Running head: Security in computing and information technology
Security in computing and information technology
Name of the Student
Name of the University
Author Note

Security in computing and information technology 1
Q1 Cryptanalysis
a)
[Cryptanalysis on Simple Substituion Cipher] (Marks 1)
Show step-by-step process to find the plaintext and the key for the following ciphertext
using the concept of simple substitution cipher ‘shift by n’ as discussed in Lecture-1:
Ciphertext: NZXMTYLETZYD. Find the plaintext using shift by n as discussed in
Lecture-1 and tutorial-1.
Simple substitution cipher is a figure that has been used for a huge number of years. It
fundamentally comprises of substituting each plaintext character for an alternate cipher text
character. It varies from the Caesar cipher in that the figure letters in order isn't just the letter
set moved, it is totally confused.
For example
The algorithm for finding the cipher text is a shown below. The 26 letters of alphabet
are used as plain text and the cipher text is the inversion of the letters of alphabet.
Plain alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher alphabet: DEFGHIJKLMNOPQRSTUVWXYZABC
So, from the above cryptanalysis formula, the cipher text was given as NZXMTYLETZYD.
In this case we have to look at the alternate letters in the position of the plain alphabet letters
Therefore, the correct plain text for the cipher text NZXMTYLETZYD
The key that is used for decoding the cipher text is FTHESANDSTAR.
a b c d e f g h i j k l m n o p q r s t u v w x y z
y s f e m n r x I b j v w l k u a d t z o g p c h q

Security in computing and information technology 2
b)
[Cryptanalysis on Double Transposition Cipher] (Marks 1.5)
Decrypt the following ciphertext using the double transposition cipher (as discussed in
the Lecture-1 and Tute-1) using a matrix of 7 rows and 8 columns.
Ciphertext:
NAGEIDVTATLNIITYNDFAOICENHANICTICPRTEYHTPTOSMRIAAYPORHGI
Hint: The first two words in the plaintext are “THE” and “CRYPTOGRAPHY”.
Solution:
N A G E I D V T R1
A T L N I I T Y R2
N D F A O I C E R3
N H A N I C T I R4
C P R T E Y H T R5
P T O S M R I A R6
A Y P O R H G I R7
C1 C2 C3 C4 C5 C6 C7 C8
4 7 5 1 3 6 2 1
E V I N G D A N 1
N T I A L I T A 2
A C O N F I D N 3
N T I N A C H N 4