Key generation is a process done while a device wants to pair with another device. The process is independent of any other LE device. The reason to generate a key and pair the device with another device are:

• Securing device identity
• Authentication of the unencrypted data.
• Confidentiality

For key generation purposes the devices exchange required information and then the Short Term Key (STK) is calculated. The link is then encrypted used AES-CCM cryptography. While the key generation is not performed on the controller, the actual encryption is performed on the controller.