java me - AES Encryption/Decryption with Bouncycastle Example in J2ME

Question

i want to Encrypt and Decrypt data in J2ME using AES Algorithm with bouncy castle can any one give me sample code for that

i want to use ECB with PKCS5Padding

Thanks in Advance.

Answer 1

I'm sure there are examples out there but I haven't found them. Here are a few hints to help you get started. You need to learn how to connect the BC classes together. First, get the bouncycastle source code and be prepared to look at it when you have questions. It's actually very readable so don't be afraid to examine it when the documentation is poor. For example, many classes want an instance of a CipherParameters object, but it is rare for the documentation to specify any more detail. However, in the source code it will be obvious as to which implementing classes are expected.

Choose one of the AES engines, for example AESEngine, as the encryption engine. Next pick a mode; ECB is rarely correct, so for example if you pick CBC mode then create a CBCBlockCipher object from your AESEngine object. Next, use this object to create a PaddedBufferBlockCipher object. The default constructor uses PKCS7 padding which is identical to the PKCS5 padding you want. Now you need to create an object to hold the key and IV. This is the CipherParameters interface. You create the object in two steps. First, you create a KeyParameter object with your key. Next, you create a ParametersWithIV object with your KeyParameter object and your IV. This object is supplied to the init method of the PaddedBufferBlockCipher object and then your are ready to go.

EDIT

Here is small example:

private static byte[] cipherData(PaddedBufferedBlockCipher cipher, byte[] data)
        throws Exception
{
    int minSize = cipher.getOutputSize(data.length);
    byte[] outBuf = new byte[minSize];
    int length1 = cipher.processBytes(data, 0, data.length, outBuf, 0);
    int length2 = cipher.doFinal(outBuf, length1);
    int actualLength = length1 + length2;
    byte[] result = new byte[actualLength];
    System.arraycopy(outBuf, 0, result, 0, result.length);
    return result;
}

private static byte[] decrypt(byte[] cipher, byte[] key, byte[] iv) throws Exception
{
    PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CBCBlockCipher(
            new AESEngine()));
    CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key), iv);
    aes.init(false, ivAndKey);
    return cipherData(aes, cipher);
}

private static byte[] encrypt(byte[] plain, byte[] key, byte[] iv) throws Exception
{
    PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(new CBCBlockCipher(
            new AESEngine()));
    CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key), iv);
    aes.init(true, ivAndKey);
    return cipherData(aes, plain);
}