md5.update(opad);
        return md5.digest(digest);
    }

    protected int engineDigest(byte[] buf, int offset, int len) {
        byte[] digest = md5.digest();
        md5.update(opad);
        md5.update(digest);
        try {
            return md5.digest(buf, offset, len);
        } catch (Exception ex) {
            throw new IllegalStateException();
        }
    }

        return this.md5.digest(digest);
    }


    @Override
    protected int engineDigest ( byte[] buf, int offset, int len ) {
        byte[] digest = this.md5.digest();
        this.md5.update(this.opad);
        this.md5.update(digest);
        try {
            return this.md5.digest(buf, offset, len);
        }
        catch ( Exception ex ) {
            throw new IllegalStateException();
        }
    }