Password is a symbol compiled according to a specific law, which is used to transmit the information of both parties. 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.
In 405 BC, the Peloponnesian War between Athens and Sparta in ancient Greece ended. The Spartan army gradually occupied the dominant position and prepared to launch the final attack on Athens. At this time, the Persian Empire, which had stood on the side of Sparta, suddenly changed its attitude and stopped its aid to Sparta, with the intention of making Athens and Sparta lose both sides in the continuous war in order to profit from it. In this case, Sparta urgently needs to find out the specific action plan of the Persian Empire in order to adopt a new strategic policy. Just then, the Spartan army captured an Athenian messenger who returned to Athens from the Persian Empire to deliver letters. Spartan soldiers searched the messenger carefully, but for a long time, they found nothing except an ordinary belt full of chaotic Greek letters written by him.