Encryption And Decryption Using AES Algorithm

1.AESEncryption.java

package com.tutorial4u;

import java.text.SimpleDateFormat;

import java.util.Date;

import javax.crypto.Cipher;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

import javax.xml.bind.DatatypeConverter;

/**

 * This example program shows how AES encryption and decryption can be done in

 * Java. Please note that secret key and encrypted text is unreadable binary and

 * hence in the following program we display it in hexadecimal format of the

 * underlying bytes.

 *

 * @author ashish

 */

public class AESEncryption {

       /**

        * gets the AES encryption key. In your actual programs, this should be

        * safely stored.

        *

        * @return

        * @throws Exception

        */

       public static SecretKey getSecretEncryptionKey() throws Exception {

             Date today = new Date();

             SimpleDateFormat dateFormat = new SimpleDateFormat("ddMMyyyy");

             // Key is last 8 digits of JFS CIS_NUMBER (i.e. U65923KA2006PTC040028) +

             // DDMMYYYY

             String stringKey = "TC040028" + dateFormat.format(today);

             byte[] keyBytes = stringKey.getBytes("UTF-8");

             SecretKey secretKey = new SecretKeySpec(keyBytes, 0, keyBytes.length, "AES");

             return secretKey;

       }

       /**

        * Encrypts plainText in AES using the secret key

        *

        * @param plainText

        * @return

        * @throws Exception

        */

       public static byte[] encryptText(String plainText) throws Exception {

             // AES defaults to AES/ECB/PKCS5Padding in Java 7

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

             aesCipher.init(Cipher.ENCRYPT_MODE, getSecretEncryptionKey());

             byte[] byteCipherText = aesCipher.doFinal(plainText.getBytes());

             return byteCipherText;

       }

       /**

        * Decrypts encrypted byte array using the key used for encryption.

        *

        * @param byteCipherText

        * @return

        * @throws Exception

        */

       public static String decryptText(byte[] byteCipherText) throws Exception {

             // AES defaults to AES/ECB/PKCS5Padding in Java 7

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

             aesCipher.init(Cipher.DECRYPT_MODE, getSecretEncryptionKey());

             byte[] bytePlainText = aesCipher.doFinal(byteCipherText);

             return new String(bytePlainText);

       }

       /**

        * Convert a binary byte array into readable hex form

        *

        * @param hash

        * @return

        */

       public static String bytesToHex(byte[] hash) {

             return DatatypeConverter.printHexBinary(hash);

       }

       /**

        * Convert a readable hex to String

        *

        * @param hash

        * @return

        */

       public static byte[] hexToBytes(String hash) {

             return DatatypeConverter.parseHexBinary(hash);

       }

}

2.AESTest.java

package com.tutorial4u;

public class AESTest {

       public AESTest() {

             try {

                    String originalText = "password@#";

                    String encryptedText = AESEncryption.bytesToHex(AESEncryption.encryptText(originalText));

                    String decryptedText = AESEncryption.decryptText(AESEncryption.hexToBytes(encryptedText));

                    System.out.println("Original Text : " + originalText);

                    System.out.println("Encrypted Text (Hex Form) : " + encryptedText);

                    System.out.println("Decrypted Text : " + decryptedText);

             } catch (Exception e) {

                    // TODO Auto-generated catch block

                    e.printStackTrace();

             }

       }

       public static void main(String[] args) {

             new AESTest();

       }

}