Chiffrement et décryptage Java AES

Je voudrais chiffrer et déchiffrer un mot de passe en utilisant le cryptage AES 128 bits avec une clé de 16 octets. J'obtiens une erreur javax.crypto.BadPaddingException lors du déchiffrement de la valeur. Est-ce que je manque quelque chose pendant le décryptage?

public static void main(String args[]) {
    Test t = new Test();
    String encrypt = new String(t.encrypt("mypassword"));
    System.out.println("decrypted value:" + t.decrypt("ThisIsASecretKey", encrypt));
}

public String encrypt(String value) {
    try {
        byte[] raw = new byte[]{'T', 'h', 'i', 's', 'I', 's', 'A', 'S', 'e', 'c', 'r', 'e', 't', 'K', 'e', 'y'};
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(value.getBytes());
        System.out.println("encrypted string:" + (new String(encrypted)));
        return new String(skeySpec.getEncoded());
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IllegalBlockSizeException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (BadPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (InvalidKeyException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}

public String decrypt(String key, String encrypted) {
    try {
        SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes(), "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(skeySpec.getEncoded(), "AES"));
        //getting error here
        byte[] original = cipher.doFinal(encrypted.getBytes());
        return new String(original);
    } catch (IllegalBlockSizeException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (BadPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (InvalidKeyException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}  

Message d'erreur

encrypted string:�Bj�.�Ntk�F�`�
encrypted key:ThisIsASecretKey
decrypted value:null
May 25, 2012 12:54:02 PM bean.Test decrypt
SEVERE: null
javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)
at bean.Test.decrypt(Test.java:55)
at bean.Test.main(Test.java:24)

Enfin, j'utilise la solution suivante basée sur la réponse @ QuantumMechanic

public class Test {

public String encryptionKey;

public static void main(String args[]) {
    Test t = new Test();
    String encrypt = t.encrypt("mypassword");
    System.out.println("decrypted value:" + t.decrypt(t.encryptionKey, encrypt));
}

public String encrypt(String value) {
    try {
        // Get the KeyGenerator
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(256);
        // Generate the secret key specs.
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        String key = new Base64().encodeAsString(raw);
        this.encryptionKey = key;
        System.out.println("------------------Key------------------");
        System.out.println(key);
        System.out.println("--------------End of Key---------------");
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        String encrypt = (new Base64()).encodeAsString(cipher.doFinal(value.getBytes()));
        System.out.println("encrypted string:" + encrypt);
        return encrypt;
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IllegalBlockSizeException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (BadPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (InvalidKeyException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}

public String decrypt(String key, String encrypted) {
    try {
        Key k = new SecretKeySpec(Base64.getDecoder().decode(key), "AES");
        Cipher c = Cipher.getInstance("AES");
        c.init(Cipher.DECRYPT_MODE, k);
        byte[] decodedValue = Base64.getDecoder().decode(encrypted);
        byte[] decValue = c.doFinal(decodedValue);
        String decryptedValue = new String(decValue);
        return decryptedValue;
    } catch (IllegalBlockSizeException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (BadPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (InvalidKeyException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    } catch (NoSuchPaddingException ex) {
        Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}

}