Bellows, a java code of the Playfair Encryption and decryption: package Playfair; import java.util.Scanner; public class

[answerhappygod]

Bellows, a java code of the Playfair Encryption and
decryption:
package Playfair;
import java.util.Scanner;
public class Playfair
{ private String KeyWord=new
String();
private String Key=new
String();
private char
matrix_arr[][]= new
char[5][5];
public void setKey(String
k)
{
String K_adjust=new String();
boolean flag =
false;
K_adjust = K_adjust + k.charAt(0);
for(int i=1;
i<k.length();i++)
{
for(int
j=0;j<K_adjust.length(); j++)
{
if(k.charAt(i)==K_adjust.charAt(j))
{
flag = true;
}
}
if(flag == false)
K_adjust = K_adjust + k.charAt(i);
flag = false;
}
KeyWord=K_adjust;
}
public void KeyGen()
{
boolean flag=true;
char current;
Key=KeyWord;
for ( int i=0 ; i<26
; i++)
{
current=(char)(i+97);
if(current=='j')
continue;
for(int j=0 ; j<
KeyWord.length() ; j++ )
{
if (current == KeyWord.charAt(j))
{
flag=false;
break;
}
} if(flag)
Key=Key+current;
flag=true;
}
System.out.println(Key);
matrix ();
}
private void matrix
()
{
int counter=0;
for (int i=0 ; i<5
;i++)
{
for (int j=0 ; j<5 ;
j++)
{
matrix_arr[j]=Key.charAt(counter);
System.out.print(matrix_arr[j]);
counter++;
}
System.out.println("\n");
}
}
private String format(String old_text)
{
int i = 0;
int j = 0;
int len = 0;
String text = new String();
len = old_text.length();
for (int tmp = 0; tmp
< len; tmp++)
{
if (old_text.charAt(tmp) == 'j')
{
text = text + 'i';
}
else
text = text+old_text.charAt(tmp);
}
len = text.length();
for (i = 0; i < len; i = i + 2)
{
if (text.charAt(i+1) ==
text.charAt(i))
{
text = text.substring(0, i+1) + 'x' +
text.substring(i+1);
}
else
{}
}
return text;
}
private String [] Divid2Pairs (String
new_string)
{
String Original = format(new_string);
int size= Original.length();
if(size%2!=0)
{
size++;
Original = Original+'x';
}
String x[]= new String[size/2];
int counter=0;
for ( int i=0 ;
i<size/2 ;i++)
{
x=Original.substring(counter, counter+2);
System.out.println(x);
counter=counter+2;
}
return x;
}
public int[]
GetDiminsions(char letter)
{
int []key=new
int[2];
if ( letter == 'j')
letter='i';
for (int i=0 ; i<5
;i++)
{
for (int j=0 ; j<5 ;
j++)
{
if(matrix_arr[j] == letter)
{
key[0]=i;
key[1]=j;
break;}
}
}
return key;
}
public String Encript(String Source)
{
System.out.println("Encription Start");
String src_arr[]=Divid2Pairs(Source);
String Code=new String();
char one;
char two;
int part1[]=new
int[2];
int part2[]=new
int[2];
for (int i=0 ; i<
src_arr.length ;i++ )
{
one = src_arr.charAt(0);
two = src_arr.charAt(1);
part1 = GetDiminsions(one);
part2 = GetDiminsions(two);
if(part1[0]==part2[0])
{
if (part1[1]<4)
part1[1]++;
else
part1[1]=0;
if(part2[1]<4)
part2[1]++;
else
part2[1]=0;
}
else if
(part1[1]==part2[1])
{
if (part1[0]<4)
part1[0]++;
else
part1[0]=0;
if(part2[0]<4)
part2[0]++;
else
part2[0]=0;
}
else
{
int temp=part1[1];
part1[1]=part2[1];
part2[1]=temp;
}
Code= Code + matrix_arr[part1[0]][part1[1]] +
matrix_arr[part2[0]][part2[1]];
}
System.out.println(Code);
return Code;
}
public String Decript (String Code) {
System.out.println("Decription Start");
String Original=new String();
String src_arr[]=Divid2Pairs(Code);
char one;
char two;
int part1[]=new
int[2];
int part2[]=new
int[2];
for (int i=0 ; i<
src_arr.length ;i++ )
{
one = src_arr.charAt(0);
two = src_arr.charAt(1);
part1 = GetDiminsions(one);
part2 = GetDiminsions
(two);
if(part1[0]==part2[0])
{
if (part1[1]>0)
part1[1]--;
else
part1[1]=4;
if(part2[1]>0)
part2[1]--;
else
part2[1]=4;
}
else if
(part1[1]==part2[1])
{
if (part1[0]>0)
part1[0]--;
else
part1[0]=4;
if(part2[0]>0)
part2[0]--;
else
part2[0]=4;
}
else
{
int temp=part1[1];
part1[1]=part2[1];
part2[1]=temp ;
} Original =Original + matrix_arr[part1[0]][part1[1]]
+
matrix_arr[part2[0]][part2[1]];
}
System.out.println(Original);
return Original;
}
public static
void main(String[] args)
{
Playfair x=new Playfair();
Scanner sc = new
Scanner(System.in);
System.out.println("Enter a keyword:");
String keyword = sc.next();
x.setKey(keyword);
x.KeyGen();
System.out.println("To Encrypt enter 1 \nTo
Decript enter 2\nTesting both enter anything else:");
int choosen_value = sc.nextInt();
if(choosen_value==1)
{
System.out.println("Enter word to encrypt:");
String key_input = sc.next();
String Encripted= x.Encript(key_input);
}
else if(choosen_value==2)
{
System.out.println("Enter word to decrypt:");
String decripted = sc.next();
x.Decript(decripted);
}
else
{
System.out.println("Enter word to encrypt &
decrypt:");
String key_input = sc.next();
String Encripted= x.Encript(key_input);
x.Decript(Encripted);
} }}
Run the Playfair program
Encrypt the plaintext “holiday” with the
keyword "|exam"|
1) The program present an error; propose a solution for
encryption the plaintext “holiday”
……………………………………………………………………………………………….
2) Write the new plaintext
…………………………………………………………………………………………………
3) Write the found ciphertext
………………………………………………………………………………………………..
4) We propose to use the playfair 6*6 matrix instead of playfair
5*5 matrix.
Make the essential changes in the program for put into
consideration the new matrix size:
Ø private char matrix_arr[][]=
newchar[5][5];
…………………………………………………………………………………………………..
Ø for (int i=0 ; i<26 ;i++)
……………………………………………………………………………………………………
Ø for (int j=0 ; j<5 ;
j++)
……………………………………………………………………………………………………
Ø for (int i=0 ;
i<5;i++)
……………………………………………………………………………………………………
5) Write the new Ciphertext
.........................................................................................................................................................
……………………………………………………………………………………………………