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);

}

}

}