There must be uppercase and lowercase letters and numbers, not less than eight and not more than twenty.
Password is a confusing technology, and users want to turn normal (identifiable) information into unrecognizable information. But this unrecognizable information part can be reprocessed, recovered and cracked. Password is a general term for "password" in Chinese. In fact, the "password" entered when logging in to websites, e-mails and withdrawing money from banks should be strictly called "password" because it is not the original "encryption code", but it can also be called a secret number. A symbolic system (such as a message) that is mainly limited to personal understanding. Such as cipher telegrams and cipher typewriters.