In old fashion encryption, the sending system decodes the message by using the precise key. That key is the coin in this text. Then the receiving system decrypts the massage by using the same key that the sender uses but oppositely. If the sender encrypted the ASCII codes by using multiplication. The receiver will divide the ASCII codes by using the same encryption key. In the quantum system, the sender uses a certain group of encryption keys. The idea is that the sender doesn't know precisely which encryption key it uses. But the system knows that in the number of the keychain it used. But the sender doesn't know which number the "keychain 2" is in the receiving system. That thing makes it harder to capture the key. Each encryption key in the keychain has a certain value. In the next text. The keys are handled as physical tools like coins. So each coin is a certain key. Those values are the material (frequency), color energy level, and many other things. In the cas