Calculating bit strength

Question

I have an application which uses AES/CBC/PKCS5Padding to encrypt data. How would I calculate the bit strength of the encryption. I'm using a key entered by the user to encrypt, then this code to generate a SecretKeySpec.
        byte[] key = new byte[16];
        MessageDigest digest = MessageDigest.getInstance("MD5");
        digest.update(keystring.getBytes("UTF-8"));
        byte[] hash = digest.digest();
        int len = hash.length;
        if (len > key.length) {
            len = key.length;
        System.arraycopy(hash, 0, key, 0, len);
        return new SecretKeySpec(hash, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);How would I calculate the bit strength of the encryption?

Answer 1

Use the KeyGenerator class to generate a key once and store it in a KeyStore, retrieve it when needed using a strong password.
Or, generate a PBE key whenever needed which is still based on a string but a LOT better than just .getBytes on a string. Sun doesn't support PBE with AES, but I think the bouncycastle provider does.