A secure entry method of a secure entry system comprising a reader, and a detector, a remote controller, a locker, and a tag corresponding to peripheral devices connected to and communicating with the reader in a wireless or wired manner, the method comprising:
- a first step of transmitting and sharing a common identifier (ID), a master key, and a frequency list to and with the tag by the reader to register the tag;
- a second step of primarily encrypting data using the master key, secondarily encrypting the data using a temporary key, and transmitting the encrypted data together with the temporary key and the non-encrypted common ID to the tag on a first frequency corresponding to a designated frequency, by the reader to transmit the data to the tag in a wireless manner;
- a third step of extracting the common ID from the received data, comparing the extracted common ID to the stored common ID to primarily determine whether the reader is a registered reader, if the reader is a non-registered reader, returning to a standby mode without decrypting the data, and, if the reader is a registered reader, extracting the temporary key, primarily decrypting the received encrypted data using the temporary key, and secondarily decrypting the data using the master key to secondarily determine whether the reader is a registered reader and to check a variable frequency, by the tag;
- a fourth step of primarily encrypting data using the master key, secondarily encrypting the data using a temporary key, and transmitting the encrypted data on a second frequency corresponding to the variable frequency set by the reader, by the tag;
- and
- a fifth step of primarily decrypting the data received on the second frequency, using a temporary key, and secondarily decrypting the data using the master key to determine whether to permit entry, by the reader,
- wherein the data comprises an ID of the reader or the peripheral device, a control signal, and information about a variable frequency for next communication,
- wherein the designated frequency is defined when the system is installed, and
- wherein the variable frequency is randomly selected within the frequency list set when the system is installed.