Foundation of Cyber Security

FOUNDATION OF CYBER SECURITY 1
Foundation of Cyber Security
VENKATA THOTA
Institutional Affiliation

FOUNDATION OF CYBER SECURITY 2
Table of Contents
Question 1........................................................................................................................................4
Introduction..................................................................................................................................4
Vigenère Cipher C Program.........................................................................................................4
Program Output........................................................................................................................7
Encryption and Decryption Methods...........................................................................................8
Vigenère Cipher Robustness........................................................................................................8
Question 2........................................................................................................................................9
Data Deletion...............................................................................................................................9
Data Recovery..............................................................................................................................9
Securely Destroying Data..........................................................................................................10
Importance of Data Destruction.................................................................................................11
Question 3......................................................................................................................................12
Current State of Encrypted E-Mail Solutions............................................................................12
Extracting Information from Intercepted Emails.......................................................................13
Solution......................................................................................................................................14
Question 4......................................................................................................................................16
Start frame..................................................................................................................................16
Host Initiating Connection Mac Address...................................................................................16
Mac Address of Destination Host..............................................................................................17
Source and Destination IP Addresses........................................................................................18
Source and Destination Ports.....................................................................................................19
Conclusion.....................................................................................................................................20
Reference List................................................................................................................................22

FOUNDATION OF CYBER SECURITY 3

FOUNDATION OF CYBER SECURITY 4
Question 1
Introduction
The program provides the users with the options to enter a message and either encrypt or decrypt
it. When the program executes, the user is prompted to enter the keyword to be used in the cipher
and the paraphrase. Vigenère cipher is a type of cryptography that employs the technique of
polyalphabetic substitution for encrypting a plain message (Dey, 2012). Caesar cipher approach
can better explain the Vigenère cipher because in Caesar cipher every character of the plain
message is reshuffled to a different place while in Vigenère cipher the characters are shifted
based on distinct shift values (MushtaqSherAli and Hassan-Sarhan, 2014).
Vigenère Cipher C Program
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
main()
{
int i,j,k,numberstring[100],numberkey[100],numbercipher[100]; //declaring variables
char str[100],key[100];
printf("Enter a string\n");
gets(str);
//converting entered string to Capital letters
for(i=0,j=0;i<strlen(str);i++)
{
if(str[i]!=' ')
{
str[j]=toupper(str[i]);

FOUNDATION OF CYBER SECURITY 5
j++;
}
}
str[j]='\0';
printf("Entered string is : %s \n",str);
//Storing string in terms of ascii
for(i=0;i<strlen(str);i++)
{
numberstring[i]=str[i]-'A';
}
printf("Enter a key\n");
gets(key);
//converting entered key to Capital letters
for(i=0,j=0;i<strlen(key);i++)
{
if(key[i]!=' ')
{
key[j]=toupper(key[i]);
j++;
}
}
key[j]='\0';
//Assigning key to the string
for(i=0;i<strlen(str);)
{
for(j=0;(j<strlen(key))&&(i<strlen(str));j++)
{
numberkey[i]=key[j]-'A';

FOUNDATION OF CYBER SECURITY 6
i++;
}
}
for(i=0;i<strlen(str);i++)
{
numbercipher[i]=numberstring[i]+numberkey[i];
}
for(i=0;i<strlen(str);i++)
{
if(numbercipher[i]>25)
{
numbercipher[i]=numbercipher[i]-26;
}
}
printf("Vigenere Cipher text is\n");
for(i=0;i<strlen(str);i++)
{
printf("%c",(numbercipher[i]+'A'));
}
printf("\n");
}