Android Cipher problems. InvalidKeyException?

Question

I'm trying to create an application for Android that uses encryption to save user information and I cannot figure out what I'm doing wrong. I'm trying to create an instance of an AES cipher but the application keeps on throwing "InvalidKeyExceptions." Consider the following code:

public static final byte[] IV = new byte[]
{ 0x04, 0x08, 0x15, 0x16, 0x23, 0x42, 0x00, 0x00, 0x00, 0x00,0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f};
protected final IvParameterSpec params = new IvParameterSpec(IV);
protected Cipher myCipher;

public AESEncryptor(String passwd, InputStream source, String destinationFile)
{
    try
    {           
        myCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        Log.d("System.out.println", "Block Size: "+myCipher.getBlockSize());
        myCipher.init(Cipher.ENCRYPT_MODE, AESEncryptor.generateSecretKeyFromPassword(passwd),params);
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

I get this exception:

java.security.InvalidKeyException: initialisation vector must be the same length as block size..

The myCipher.init(...) line triggers this exception.

I understand what it's saying but according to myCipher.getBlockSize() the IV byte array should hold 16 bytes, and it does, but it doesn't work. I have also tried byte arrays of length 0-128, and nothing in that range works either.

Oh also, if I take this code, unaltered, and add it to a regular Java application, I get no errors. Compiling for Android seems to be causing this error.

Please help. Thanks, Ryan

is that the exact text of the exception? I can't find it in the openjdk, though it is possible they changed the text. — President James K. Polk
– President James K. Polk, Commented Feb 15, 2010 at 12:54
Yes, that is the exact text. The rest of the exception is just a stack trace. They might have changed the text because "initialisation" is spelled wrong... it should be "initialization." — RyanM
– RyanM, Commented Feb 15, 2010 at 13:07

H. Green · Accepted Answer · 2010-02-17 04:18:48Z

1

Have you tried specifying explicitly the block size in your mode parameter?

Ex:

Cipher.getInstance("AES/CBC16/PKCS5Padding");

I noticed here that if you don't specify the block size then it is provider dependent.

answered Feb 17, 2010 at 4:18

H. Green

7655 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

RyanM Over a year ago

Thanks for responding. Though this is a good idea, when I tried it I got the following exception: "java.security.NoSuchAlgorithmException: can't support mode CBC16". Ryan

H. Green Over a year ago

Try CBC128 since AES is a 128bit block cipher. Here's a good reference page: java.sun.com/j2se/1.4.2/docs/guide/security/jce/…

Collectives™ on Stack Overflow

Android Cipher problems. InvalidKeyException?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related