Practical No-8

AIM: Write a program to Implement RC4 algorithm .

import java.io.*;

class rc4

{

public static void main(String args[])throws IOException

            {          int temp=0;

                        String ptext;

                        String key;

                        int s[]=new int[256];

                        int k[]=new int[256];

                        DataInputStream in=new DataInputStream(System.in);

                        System.out.print("\nENTER PLAIN TEXT\t");

                        ptext=in.readLine();

                        System.out.print("\n\nENTER KEY TEXT\t\t");

                        key=in.readLine();

                        char ptextc[]=ptext.toCharArray();

                        char keyc[]=key.toCharArray();

                        int cipher[]=new int[ptext.length()];

                        int decrypt[]=new int[ptext.length()];

int ptexti[]=new int[ptext.length()];

                        int keyi[]=new int[key.length()];

                        for(int i=0;i<ptext.length();i++)

                        {          ptexti[i]=(int)ptextc[i];

                        }

                        for(int i=0;i<key.length();i++)

                        {          keyi[i]=(int)keyc[i];

                        }

                        for(int i=0;i<255;i++)

                        {

                                    s[i]=i;

                                    k[i]=keyi[i%key.length()];

                        }

                        int j=0;

                        for(int i=0;i<255;i++)

                        {

                                    j=(j+s[i]+k[i])%256;

                                    temp=s[i];

                                    s[i]=s[j];

                                    s[j]=temp;

                        }

                        int i=0;

                        j=0;

                        int z=0;

                        for(int l=0;l<ptext.length();l++)

                        {

                                    i=(l+1)%256;

                                    j=(j+s[i])%256;

                                    temp=s[i];

                                    s[i]=s[j];

                                    s[j]=temp;

                                    z=s[(s[i]+s[j])%256];

                                    cipher[l]=z^ptexti[l];

                                    decrypt[l]=z^cipher[l];

                        }

                        System.out.print("\n\nENCRYPTED:\t\t");

                        display(cipher);

                        System.out.print("\n\nDECRYPTED:\t\t");

                        display(decrypt);

            }

            static void display(int disp[])

            {

                        char convert[]=new char[disp.length];

                        for(int l=0;l<disp.length;l++)

                        {

                                    convert[l]=(char)disp[l];

                                    System.out.print(convert[l]);

                        }

            }

}

Practical No-7

Aim: Write a program to implement Blowfish algorithm

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.swing.JOptionPane;

public class blowfish

{

            public static void main(String[] args) throws Exception

 {

KeyGenerator keygen = KeyGenerator.getInstance("Blowfish");

SecretKey secretkey = keygen.generateKey();

Cipher cip = Cipher.getInstance("Blowfish");

cip.init(Cipher.ENCRYPT_MODE, secretkey);

String inputText = JOptionPane.showInputDialog(" Give Input: ");

byte[] encrypted = cip.doFinal(inputText.getBytes());

cip.init(Cipher.DECRYPT_MODE, secretkey);

byte[] decrypted = cip.doFinal(encrypted);

JOptionPane.showMessageDialog(JOptionPane.getRootFrame(),"encrypted : " +     new String(encrypted) + "\n" +"decrypted : " + new String(decrypted));

System.exit(0);

}

}

Practical No-6

AIM- Write a program to implement RSA algorithm in Java

import java.math.BigInteger;

import java.security.SecureRandom;

public class rsa

{

            private BigInteger n, d, e;

             private int bitlen = 1024;

              public rsa(BigInteger newn, BigInteger newe)

             {

                        n = newn;

                        e = newe;

            }

 public rsa(int bits)

{

                        bitlen = bits;

                        SecureRandom r = new SecureRandom();

                        BigInteger p = new BigInteger(bitlen / 2, 100, r);

                          BigInteger q = new BigInteger(bitlen / 2, 100, r);

                         n = p.multiply(q);

                        BigInteger m = (p.subtract(BigInteger.ONE)).multiply(q.subtract(BigInteger.ONE));

                        e = new BigInteger("3");

  while (m.gcd(e).intValue() > 1)

 {

                                     e = e.add(new BigInteger("2"));

                        }

                         d = e.modInverse(m);

             }

public synchronized BigInteger encrypt(BigInteger message)

 {

                         return message.modPow(e, n);

            }

 public synchronized BigInteger decrypt(BigInteger message)

{

                        return message.modPow(d, n);

}

public static void main(String[] args)

{

                         rsa rsa = new rsa(1024);

                        String text1 = "SERO";

                         System.out.println("Plaintext: " + text1);

                        BigInteger plaintext = new BigInteger(text1.getBytes());

                        BigInteger ciphertext = rsa.encrypt(plaintext);

                         System.out.println("Ciphertext: " + ciphertext);

                          plaintext = rsa.decrypt(ciphertext);

                           String text2 = new String(plaintext.toByteArray());

                         System.out.println("Plaintext: " + text2);

             }

}

Practical No-5

Aim: Write a program to implement AES algorithm.

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.swing.JOptionPane;

public class aes

{

            public static void main(String[] args) throws Exception

 {

KeyGenerator keygen = KeyGenerator.getInstance("AES");

SecretKey secretkey = keygen.generateKey();

Cipher cip = Cipher.getInstance("AES");

cip.init(Cipher.ENCRYPT_MODE, secretkey);

String inputText = JOptionPane.showInputDialog(" Give Input: ");

byte[] encrypted = cip.doFinal(inputText.getBytes());

cip.init(Cipher.DECRYPT_MODE, secretkey);

byte[] decrypted = cip.doFinal(encrypted);

JOptionPane.showMessageDialog(JOptionPane.getRootFrame(),"encrypted : " +     new String(encrypted) + "\n" +"decrypted : " + new String(decrypted));

System.exit(0);

}

}

Practical No-4

Aim: Write a program to implement DES algorithm.

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.swing.JOptionPane;

public class aes

{

            public static void main(String[] args) throws Exception

 {

KeyGenerator keygen = KeyGenerator.getInstance("AES");

SecretKey secretkey = keygen.generateKey();

Cipher cip = Cipher.getInstance("AES");

cip.init(Cipher.ENCRYPT_MODE, secretkey);

String inputText = JOptionPane.showInputDialog(" Give Input: ");

byte[] encrypted = cip.doFinal(inputText.getBytes());

cip.init(Cipher.DECRYPT_MODE, secretkey);

byte[] decrypted = cip.doFinal(encrypted);

JOptionPane.showMessageDialog(JOptionPane.getRootFrame(),"encrypted : " +     new String(encrypted) + "\n" +"decrypted : " + new String(decrypted));

System.exit(0);

}

}

Practical No-3

AIM: To Implement Diffie-Hellman Key Exchange Algorithm in Java

 import java.util.*;

import java.math.BigInteger.*;

import java.math.*;

class diffiehellman

{public static void main(String args[])

{

BigInteger A, B, K1, K2, x, y, g, n;

Scanner s = new Scanner(System.in);

System.out.println("Enter A’s prime number!");

n = s.nextBigInteger();

System.out.println("Enter B’s prime number!");

g = s.nextBigInteger();

System.out.println("Enter A’s secret key!");

x = s.nextBigInteger();

System.out.println("This key is sent to B!");

System.out.println("Enter B’s secret key!");

y = s.nextBigInteger();

System.out.println("This key is sent to A!");

A = g.modPow(x, n);

B = g.modPow(y, n);

K1 = B.modPow(x, n);

K2 = A.modPow(y, n);

System.out.println("A’s key is " + K1);

System.out.println("B’s key is " + K2);

}

}

Practical No-2(b)

AIM- Write a program to Implement vernam cipher(one time pad) in Java

import java.lang.Math;

public class vernamcipher

 {

public static void main(String args[])

{

String text = new String("vernam");

char[] arText = text.toCharArray();

String cipher = new String("abcdef");

char[] arCipher = cipher.toCharArray();

char[] encoded = new char[5];

System.out.println("Encoded " + text + " to be… ");

for (int i = 0; i < arText.length; i++)

{

encoded[i] = (char) (arText[i] ^ arCipher[i]);

System.out.print(encoded[i]);

}

System.out.println("\nDecoded to be… ");

for (int i = 0; i < encoded.length; i++)

{

char temp = (char) (encoded[i] ^ arCipher[i]);

System.out.print(temp);

}

}

}

Practical No -2(a)

AIM – Write a program to implement Railfence algorithm.

public class railfence

{

              public static void main(String args[])

             {

                        String input = "inputstring";

                         String output = "";

                        int len = input.length(),flag = 0;

                        System.out.println("Input String : " + input);

                         for(int i=0;i<len;i+=2)

{

                                     output += input.charAt(i);

                        }

                        for(int i=1;i<len;i+=2)

{

                                       output += input.charAt(i);

                        }      

                        System.out.println("Cipher Text : "+output);

            }

}

OUTPUT-

Input String : inputstring

Cipher Text : ipttignusrn

Practical No-1(c)

Aim: Write a program to implement Monoalphabetic Substitution Cipher Technique.

public class monoalphabetic

{

             public static void main(String[] args)

{

                        String plaintext = "hello";

                        char[] myarr = plaintext.toCharArray();

                        for(int count=0 ; count < myarr.length ; count++)

                        {

                                    char cipher = myarr[count]; 

                                    switch (cipher)

                                    {

 case 'a':

                                                            System.out.print("z");

                                                break;

                                                case 'b':

                                                              System.out.print("y");

                                                 break;

                                                 case 'c':

                                                            System.out.print("x");

                                                 break;

                                                 case 'd':

                                                             System.out.print("w");

                                                break;

                                                case 'e':

                                                             System.out.print("v");

                                                  break;

                                                case 'f':

                                                             System.out.print("u");

                                                 break;

                                                  case 'g':

                                                            System.out.print("t");

                                                break;

                                                case 'h':

                                                            System.out.print("s");

   break;

                                                  case 'i':

                                                             System.out.print("r");

                                                break;

                                                case 'j':

                                                             System.out.print("q");

                                                  break;

                                                case 'k':

                                                            System.out.print("p");

                                                 break;

                                                case 'l':

                                                            System.out.print("o");

                                                   break;

                                                 case 'm':

                                                            System.out.print("n");

                                                break;

                                    case 'n':

                                                System.out.print("m");

                                    break;

                                     case 'o':

                                                   System.out.print("l");

                                    break;

                                      case 'p':

                                                 System.out.print("k");

                                     break;

                                    case 'q':

                                                 System.out.print("j");

                                    break;

                                      case 'r':

    System.out.print("i");

                                      break;

                                     case 's':

    System.out.print("h");

                                      break;

                                      case 't':

                                                   System.out.print("g");

                                     break;

                                      case 'u':

    System.out.print("f");

                                      break;

                                      case 'v':

  System.out.print("e");

                                     break;

                                    case 'w':

                                                   System.out.print("d");

                                     break;

                                    case 'x':

                                                   System.out.print("c");

                                     break;

                                      case 'y':

                                                System.out.print("b");

                                      break;

                                    case 'z':

                                                System.out.print("a");

                                    break;

                                      case ' ':

                                                  System.out.print("1");

                                     break;

   case '1':

                                                  System.out.print(" ");

 }

                         }

}

}