BouncyCastle in Java

Question

Hi,
I developing a project which involve cryptography provided by BouncyCastle. May anyone provides me an example of doing AES symmetric cipher by using the APIs in BouncyCastle?
Thanks in advance

Answer 1

In "Practical Cryptography", Ferguson & Schneier simply state:
"Do not ever use ECB for anything. It has serious weaknesses, and
is only included here so that we can warn you away from it."
Basically, identical plaintext is encrypted to identical ciphertext.
This site shows you what this looks like with some image files.
http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation
So you should not use it unless you absolutely have to. Use CBC
instead.
With that said, I can imagine you may be forced to interface with
some poorly designed legacy application that used ECB, so you
may have no choice.
In that case, I'll tell you how to use ECB with BouncyCastle.
Its the default mode for their AESEngine. That means, if you
don't pass in the AESEngine wrapped in a moded block cipher,
you'll end up with ECB. For your code above, simply remove
the "new CBCBlockCipher(engine)" and just pass "engine" directly
into the PaddedBufferedBlockCipher.
And fireflying, Im guessing your desire to use ECB might be an
attempt to alleviate the unwanted padding bytes... I understand
situations where using the JCE is not an option. Ive had to write
code for clients who've actually removed the JCE from their
1.4 JDK(believe it or not!). So, to answer your question about
the padding bytes, here's a little method Ive used:
public static byte[] stripPadding(byte[] b) {
        int len = 0;
        for (int i = 0; i < b.length; i++) {
            if (b[i] == 0x00) {
                len = i;
                break;
        byte[] out = new byte[len];
        System.arraycopy(b, 0, out, 0, len);
        return out;
    }