Here is a code of encryption and decryption using RSA algorithm

import java.io.*;
import java.security.*;
import javax.crypto.*;

class EncryptAndDecrypt {

public static void main (String[] args) throws Exception{
KeyPairGenerator keygenerator = KeyPairGenerator.getInstance("RSA");
SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");
keygenerator.initialize(1024, random);

KeyPair keypair = keygenerator.generateKeyPair();
PrivateKey privateKey = keypair.getPrivate();
PublicKey publicKey = keypair.getPublic();
Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.ENCRYPT_MODE, publicKey);
String st= "roseindia";
byte[] cleartext = null;
cleartext = st.getBytes();
byte[] ciphertext = null;
ciphertext = cipher.doFinal(cleartext);
System.out.println("the encrypted text is: " + ciphertext.toString());

cipher.init(Cipher.DECRYPT_MODE, privateKey);
byte[] cleartext1 = cipher.doFinal(ciphertext);
System.out.println("the decrypted cleartext is: " + new String(cleartext1));
}
}

Here is a code of encryption and decryption using DES algorithm.

import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.DESKeySpec;

class EncryptAndDecrypt {

public static void main (String[] args) throws Exception{ //KeyPairGenerator keygenerator = KeyPairGenerator.getInstance("RC4"); SecretKeyFactory key = SecretKeyFactory.getInstance("DES"); SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN"); //keygenerator.initialize(1024, random); byte[] desKeyData = { (byte)0x01, (byte)0x02, (byte)0x03, (byte)0x04, (byte)0x05, (byte)0x06, (byte)0x07, (byte)0x08 }; DESKeySpec desKeySpec = new DESKeySpec(desKeyData);

//KeyPair keypair = keygenerator.generateKeyPair(); Key keys = key.generateSecret(desKeySpec); //PrivateKey privateKey = keypair.getPrivate(); //PublicKey publicKey = keypair.getPublic();

Cipher cipher = Cipher.getInstance("DES");

System.out.println("publicKey="+keys.toString()); //System.out.println("privateKey="+privateKey.toString());

cipher.init(Cipher.ENCRYPT_MODE, keys); String st= "Welcome"; byte[] cleartext = null; cleartext = st.getBytes(); byte[] ciphertext = null; ciphertext = cipher.doFinal(cleartext); System.out.println("the encrypted text is: " + ciphertext.toString());

cipher.init(Cipher.DECRYPT_MODE, keys); byte[] cleartext1 = cipher.doFinal(ciphertext); System.out.println("the decrypted cleartext is: " + new String(cleartext1)); } }

Here is a code of encryption and decryption using AES algorithm.

import java.security.spec.AlgorithmParameterSpec;
  import javax.crypto.Cipher;
  import javax.crypto.spec.IvParameterSpec;
  import javax.crypto.spec.SecretKeySpec;
  import sun.misc.BASE64Encoder;

  /*  Mode = CipherMode.CBC,-( Cipher-block chaining)
      Padding = PaddingMode.PKCS7 or PKCS5,
      KeySize = 128,
      BlockSize = 128,
      Key = keyBytes - password,
      IV = keyBytes  - password*/

  public class testencrypt {


 Cipher cipher; 
 // Input encrypted String
 static  String input = "Hi This is my String";
 // password for encryption
  final static String strPassword = "password12345678";

 // put this as key in AES
 static SecretKeySpec key = new SecretKeySpec(strPassword.getBytes(), "AES");

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

  // Parameter specific algorithm
 AlgorithmParameterSpec paramSpec = new IvParameterSpec(strPassword.getBytes()); 

  //Whatever you want to encrypt/decrypt
  Cipher cipher =  Cipher.getInstance("AES/CBC/PKCS5Padding");

   // You can use ENCRYPT_MODE (ENCRYPTunderscoreMODE)  or DECRYPT_MODE (DECRYPT underscore MODE) 
   cipher.init(Cipher.ENCRYPT_MODE, key, paramSpec); 

  // encrypt data 
   byte[] ecrypted = cipher.doFinal(input.getBytes());

   // encode data using standard encoder
   String output =  new BASE64Encoder().encode(ecrypted);

   System.out.println("Orginal tring: " + input);
   System.out.println("Encripted string: " + output);

   }
}