In fact, as a software developer, it is really important to study good software encryption, but it is also necessary to know more about the encryption dog decryption and crack the knowledge, encryption and crack like a spear and shield, the more you know about decryption knowledge, the better the encryption code you write, to know that encryption is always easier than decryption, only know yourself and your enemy, you can win. Hardware encryption lock, the common term \"dongle\