AES-256 and PKCS7Padding fails in Java

问题

I have a couple of library, C#, PHP and Android where they all encrypt/decrypt a string in the same way so they are all compatible with each other, i.e. C# writes and encrypts data to a database and PHP can successfully decrypt it and return the original string.

I now need to do the same thing with a standard Java application, so I've taken the code from my Android library and need libraries but I am getting an exception. As far as I know the code wasn't Android specific so it shouldn't be a problem.

Below is my encryption function

public static String encrypt(String plainPasword)
    {
            String password = "";
            try
            {
                SecretKeySpec key = new SecretKeySpec("hcxilkqbbhczfeultgbskdmaunivmfuo".getBytes("US-ASCII"), "AES");
                IvParameterSpec iv = new IvParameterSpec("ryojvlzmdalyglrj".getBytes("US-ASCII"));

                Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");

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

                byte[] encoded = cipher.doFinal(plainPasword.getBytes());
                password = new String(Base64.encodeBase64(encoded));

            }
            catch (Exception ex)
            {
                System.err.println("Encryption Exception: " + ex.toString());
            }
            return password;
    }

When I call Encryption.encrypt("myString") I get the following exception:

Encryption Exception: java.security.NoSuchAlgorithmException: Cannot find any provider supporting AES/CBC/PKCS7Padding

As I said this code is working fine on Android and it shouldn't make any difference where it is running from.

Update

I found that I needed PKCS5Padding instead of 7 thanks to a link on a comment. I am now though getting the following exception:

Encryption Exception: java.security.InvalidKeyException: Illegal key size

回答1:

First, in Java, the standard padding name is PKCS5Padding, not PKCS7Padding. Java is actually performing PKCS #7 padding, but in the JCA specification, PKCS5Padding is the name given.

Next, you are trying to use AES-256, so you'll need to install the Unlimited Strength Jurisdiction policy files.

Hopefully this is just an example and you aren't using the same IV for every message, right?

回答2:

@Boardy If you are still facing the issue then i think you have to use MessageDigest which is compatible for both for C# and Java. I have faced the similar issue for AES 256 encryption and decryption. The sample code will be as follows.

public static String encryptWithAES256(String strToEncrypt) throws Exception
{
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    byte[] encodedhash = digest.digest(KEY.getBytes(StandardCharsets.UTF_8));
    IvParameterSpec ivspec = new IvParameterSpec(Arrays.copyOf(KEY.getBytes(),16));
    SecretKeySpec secretKey = new SecretKeySpec(encodedhash, AES_ENCRYPTION_ALGORITHM);
    Cipher cipher = Cipher.getInstance(CIPHER_TRANSFORMATION);
    cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivspec);
    return new String(Base64.encodeBase64(cipher.doFinal(strToEncrypt.getBytes(CHARACTER_ENCODING))));
}

来源：https://stackoverflow.com/questions/25942165/aes-256-and-pkcs7padding-fails-in-java

标签

java

encryption

aes

jce

pkcs#7