Bluetooth provides support for security in the form of device pairing, device authentication, communication encryption, and authorization.
When two Bluetooth devices come into contact with each other for the first time, they may establish a shared secret. The creation of a shared secret is called “pairing,” and it usually requires the users of both devices to enter a shared secret code in both devices using an appropriate user interface. After the pairing has been done successfully, the shared secret may be stored by each device and may be used for any future device authentication between the two devices.
Applications running on authenticated devices may optionally use encryption to prevent eavesdroppers from listening in on the shared communication between applications.
Another security option is called authorization. It is used on a per-connection basis to grant permission for a connection from another Bluetooth device. A trusted device is a device that always passes authorization and may connect to any service on the local device. A device that is not trusted usually requires the user to accept the connection.
Each Bluetooth security level requires the previous underlying security level. Device authentication requires device pairing. Encryption requires device authentication.