AES-256 and PKCS7Padding fails in Java

Question

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

http://stackoverflow.com/questions/10193567/java-security-nosuchalgorithmexception-cannot-find-any-provider-supporting-aes — srkavin, Sep 19 '14 at 20:50
Thanks when I googled I didn't find anything although now that I've changed it is now telling me that the key is an invalid size — Boardy, Sep 19 '14 at 20:54
You will need Unlimited strength JCE policy files. http://deveshsharma.info/2012/10/09/fixing-java-security-invalidkeyexception-illegal-key-size-exception/ — srkavin, Sep 19 '14 at 20:59
PKCS#7 padding is a super set of PKCS#5 padding and is many times refered to when PKCS#7 padding it what is needed. Essentially PKCS#5 is only defined for a block size of 8-bytes and PKCS#7 just extends the definition to 255-bytes. Additionally if would be very uncommon to fine an implementation of PKCS#5 that did not also support PKCS#7, in practice the two can be used interchangeably.. See [PKCS#7 padding](https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7). — zaph, Sep 01 '16 at 21:53

score 19 · Accepted Answer · answered Sep 19 '14 at 21:08

19

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?

answered Sep 19 '14 at 21:08

erickson

265,237
58
395
493

It is just an example, I have copied the policies but I am still getting the same exceptin – Boardy Sep 19 '14 at 21:09
You probably got the wrong version or put them in the wrong place. You'll need to provide more detail or just carefully review what you did. – erickson Sep 19 '14 at 21:14
1

I found the problem. I had copied the files in to Program Files\Java\jre\... but I was using a jre bundled inside the JDK directory. I copied the files into this and its all working now. Thanks for your help. Its a bit strange though to me why Android doesn't have any of these problems, especially as I am using the same library – Boardy Sep 19 '14 at 21:59
4

You are *not* using the same library. Android implements the Java SE API, but does not use the same source code, not the same provider and the AES restrictions are not implemented either. – Maarten Bodewes Sep 21 '14 at 13:47

AES-256 and PKCS7Padding fails in Java

Update

1 Answers1

Linked