You know that Resolvable Private Addresses (RPA) can be changed at regular intervals, can be resolved and are used by Privacy enabled devices.
Every Privacy-enabled BLE device has a unique address called the Identity Address. The Identity Address is the Public Address or Static Address of the BLE device. Every Privacy-enabled BLE device also has an Identity Resolving Key (IRK). The IRK is used by the BLE device to generate its RPA and is used by peer devices to resolve the RPA of the BLE device. Both the Identity Address and the IRK are exchanged during the third stage of the pairing process. Privacy-enabled BLE devices maintain a list that consists of the peer device’s Identity Address, the local IRK used by the BLE device to generate its RPA, and the peer device’s IRK used to resolve the peer device’s RPA. This is called the Resolving List.
Please refer the section 7. Link Layer (LL) Privacy for more details on Privacy.