/**

http://stackoverflow.com/questions/4551263/how-can-i-convert-string-to-secretkey

Note:- To use "AES/GCM/NoPadding" mode encryption in Java 7, replace the code for the IvParameterSpec

with 'GCMParameterSpec params = new GCMParameterSpec(blockSize * Byte.SIZE, ivData);' and don't forget

to handle the AEADBadTagException to catch integrity exceptions. Bouncy will work by simply using

"AES/GCM/NoPadding" and will throw a BadPaddingException, returning null.

//=============== usage ===================

String plain = "Zaphod's just zis guy, ya knöw?";

String encrypted = encrypt(plain, "000102030405060708090A0B0C0D0E0F");

System.out.println(encrypted);

String decrypted = decrypt(encrypted, "000102030405060708090A0B0C0D0E0F");

if (decrypted != null && decrypted.equals(plain)) {

System.out.println("Hey! " + decrypted);

} else {

System.out.println("Bummer!");

}

*/

//=================Code===================

import javax.crypto.Cipher;

import javax.crypto.spec.IvParameterSpec;

import javax.crypto.spec.SecretKeySpec;

public class CryptUtils {

public static String encrypt(final String plainMessage,

final String symKeyHex) {

final byte[] symKeyData = DatatypeConverter.parseHexBinary(symKeyHex);

final byte[] encodedMessage = plainMessage.getBytes(Charset

.forName("UTF-8"));

try {

final Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

final int blockSize = cipher.getBlockSize();

// create the key

final SecretKeySpec symKey = new SecretKeySpec(symKeyData, "AES");

// generate random IV using block size (possibly create a method for

// this)

final byte[] ivData = new byte[blockSize];

final SecureRandom rnd = SecureRandom.getInstance("SHA1PRNG");

rnd.nextBytes(ivData);

final IvParameterSpec iv = new IvParameterSpec(ivData);

cipher.init(Cipher.ENCRYPT_MODE, symKey, iv);

final byte[] encryptedMessage = cipher.doFinal(encodedMessage);

// concatenate IV and encrypted message

final byte[] ivAndEncryptedMessage = new byte[ivData.length

+ encryptedMessage.length];

System.arraycopy(ivData, 0, ivAndEncryptedMessage, 0, blockSize);

System.arraycopy(encryptedMessage, 0, ivAndEncryptedMessage,

blockSize, encryptedMessage.length);

final String ivAndEncryptedMessageBase64 = DatatypeConverter

.printBase64Binary(ivAndEncryptedMessage);

return ivAndEncryptedMessageBase64;

} catch (InvalidKeyException e) {

throw new IllegalArgumentException(

"key argument does not contain a valid AES key");

} catch (GeneralSecurityException e) {

throw new IllegalStateException(

"Unexpected exception during encryption", e);

}

}

public static String decrypt(final String ivAndEncryptedMessageBase64,

final String symKeyHex) {

final byte[] symKeyData = DatatypeConverter.parseHexBinary(symKeyHex);

final byte[] ivAndEncryptedMessage = DatatypeConverter

.parseBase64Binary(ivAndEncryptedMessageBase64);

try {

final Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

final int blockSize = cipher.getBlockSize();

// create the key

final SecretKeySpec symKey = new SecretKeySpec(symKeyData, "AES");

// retrieve random IV from start of the received message

final byte[] ivData = new byte[blockSize];

System.arraycopy(ivAndEncryptedMessage, 0, ivData, 0, blockSize);

final IvParameterSpec iv = new IvParameterSpec(ivData);

// retrieve the encrypted message itself

final byte[] encryptedMessage = new byte[ivAndEncryptedMessage.length

- blockSize];

System.arraycopy(ivAndEncryptedMessage, blockSize,

encryptedMessage, 0, encryptedMessage.length);

cipher.init(Cipher.DECRYPT_MODE, symKey, iv);

final byte[] encodedMessage = cipher.doFinal(encryptedMessage);

// concatenate IV and encrypted message

final String message = new String(encodedMessage,

Charset.forName("UTF-8"));

return message;

} catch (InvalidKeyException e) {

throw new IllegalArgumentException(

"key argument does not contain a valid AES key");

} catch (BadPaddingException e) {

// you'd better know about padding oracle attacks

return null;

} catch (GeneralSecurityException e) {

throw new IllegalStateException(

"Unexpected exception during decryption", e);

}

}

}