我试图实现基于密码的加密算法，但是我得到了这个例外:

异常: 给定的最终块没有正确填充

有什么问题吗？

这是我的代码:

public class PasswordCrypter {


private Key key;


public PasswordCrypter(String password)  {
try{
KeyGenerator generator;
generator = KeyGenerator.getInstance("DES");
SecureRandom sec = new SecureRandom(password.getBytes());
generator.init(sec);
key = generator.generateKey();
} catch (Exception e) {
e.printStackTrace();
}
}




public byte[] encrypt(byte[] array) throws CrypterException {
try{
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key);


return cipher.doFinal(array);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}


public byte[] decrypt(byte[] array) throws CrypterException{
try{
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, key);


return cipher.doFinal(array);
} catch(Exception e ){
e.printStackTrace();
}
return null;
}
}

(JUnit 测试)

public class PasswordCrypterTest {


private static final byte[] MESSAGE = "Alpacas are awesome!".getBytes();
private PasswordCrypter[] passwordCrypters;
private byte[][] encryptedMessages;


@Before
public void setUp() {
passwordCrypters = new PasswordCrypter[] {
new PasswordCrypter("passwd"),
new PasswordCrypter("passwd"),
new PasswordCrypter("otherPasswd")
};


encryptedMessages = new byte[passwordCrypters.length][];
for (int i = 0; i < passwordCrypters.length; i++) {
encryptedMessages[i] = passwordCrypters[i].encrypt(MESSAGE);
}
}


@Test
public void testEncrypt() {
for (byte[] encryptedMessage : encryptedMessages) {
assertFalse(Arrays.equals(MESSAGE, encryptedMessage));
}


assertFalse(Arrays.equals(encryptedMessages[0], encryptedMessages[2]));
assertFalse(Arrays.equals(encryptedMessages[1], encryptedMessages[2]));
}


@Test
public void testDecrypt() {
for (int i = 0; i < passwordCrypters.length; i++) {
assertArrayEquals(MESSAGE, passwordCrypters[i].decrypt(encryptedMessages[i]));
}


assertArrayEquals(MESSAGE, passwordCrypters[0].decrypt(encryptedMessages[1]));
assertArrayEquals(MESSAGE, passwordCrypters[1].decrypt(encryptedMessages[0]));


try {
assertFalse(Arrays.equals(MESSAGE, passwordCrypters[0].decrypt(encryptedMessages[2])));
} catch (CrypterException e) {
// Anything goes as long as the above statement is not true.
}


try {
assertFalse(Arrays.equals(MESSAGE, passwordCrypters[2].decrypt(encryptedMessages[1])));
} catch (CrypterException e) {
// Anything goes as long as the above statement is not true.
}
}
}