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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);
} }}
Classic Ciphers: Substitution Encryption with Playfair Cipher 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; Page 2 of 7
} 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[i][j]); counter++; } System.out.println("\n"); private String format(String old_text) { int i = 0; int i = 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 O } 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 [ ] = new String[size/2]; Page 3 of 7
int counter=0; for (int i=0; i<size/2 ;i++) x[i]=Original.substring(counter, counter+2); System.out.println(x[i]); counter=counter+2; } return x; 3 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[i][j] letter) key[@]=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 parti[]=new int[2]; int part2[ ]=new int[2]; for (int i=0; i< src_arr. length ;i++) { one = src_arr[i].charAt(0); two = src_arr[i].charAt(1); parti = 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]) Page 4 of 7
if (part1[@]<4) part1[0]++; else part1[0]=0; if(part2[@]<4) part2[@]++; else part2[@]=0; } else { int temp=part1[1]; part1[1]=part2[1]; part2[1]=temp; } Code= Code + matrix_arr[part1[@]][part1[1]] + matrix_arr (part2[@]][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 parti[]=new int[2]; int part2[]=new int[2]; for (int i=0; i< src_arr.length; i++) { one = src_arr[i].charAt(); two = src_arr[i].charAt(1); part1 = GetDiminsions (one); part2 = GetDiminsions (two); if(part1[@]==part2[@]) { 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) part1[0]--; else part1[@]=4; if(part2[@]>0) Page 5 of 7
part2[0]; else part2[@]=4; } else { int temp=part1[1]; part1[1]=part2[1]; part2[1]=temp; } Original =Original + matrix_arr(part1[@]][part1[1]] + matrix_arr(part2[@]](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); }}} Page 6 of 7
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: > private char matrix_arr [11]newchar[5][5]; for (int i=0; i<26 ;i++) for (int j=0; j<5; j++) for (int i=0; i<5;i++) 5) Write the new Ciphertext Page 7 of 7