Our country implements classified management of passwords, which can be divided into several categories.

In China, passwords are classified into core passwords, common passwords and commercial passwords.

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. Symbolic system mainly limited to personal understanding. Such as cipher telegrams and cipher typewriters.

Password is a symbol compiled according to a specific law, which is used to transmit the information of both parties. In other words, a password is a series of symbols that hide the real content. It changes the information expressed by an open and standard information code into an information code that can't be read by anyone except the two communication parties through a transformation method. This unique information code is a password.

Cryptography is a science with a long history. In the war between ancient Greece and the Persian Empire, passwords were used to transmit secret information. In modern wars, the transmission of information and the command of war are inseparable from passwords, and so is the diplomatic struggle. Passwords are generally used for the confidentiality of information communication transmission and storage.

Letters from Nazi agents with conclusive evidence usually include:

1, the text is rambling and unfocused. The letter was sent to neutral countries, and many stamps were attached to the envelope.

2. Difficult and rarely used phrases in letters are one of the signs of hiding passwords.

3. The list of people in the letter and the contents of large sections about the bridge section will also cause doubts.