The identity API provides facilities for querying and configuring your device‘s addresses. BLE’s addressing scheme is quite involved; the summary that follows is only a brief introduction.
BLE defines four address types:
Type | Description | Identity? | Configured with |
---|---|---|---|
Public | Address assigned by manufacturer; the three most significant bytes form the manufacturer's OUI. | Yes | N/A; read from controller at startup. |
Static random | Randomly generated address. | Yes | ble_hs_id_set_rnd() |
Resolvable private (RPA) | Address randomly generated from an identity address and an identity resolving key (IRK). | No | N/A; generated by controller periodically. |
Non-resolvable private (NRPA) | Randomly generated address. | No | ble_hs_id_set_rnd() |
The third column in the above table indicates the identity property of each address type. An identity address never changes, and a device can be identified by one of its unique identity addresses.
Non-identity addresses are used by devices supporting BLE privacy. A device using the privacy feature frequently changes its own address to a newly-generated non-identity address. By cycling its address, the device makes it impossible for eavesdroppers to track its location.
A device can have up to two identity addresses at once: one public and one static random. As indicated in the above table, the public identity address cannot be configured; the static random identity address can be set by calling ble_hs_id_set_rnd().
The address type is selected on a per-GAP-procedure basis. Each time you initiate a GAP procedure, you indicate which address type the device should use for the duration of the procedure.
#include "host/ble_hs.h"
None.
Function | Description |
---|---|
ble_hs_id_copy_addr | Retrieves one of the device's identity addresses. |
ble_hs_id_gen_rnd | Generates a new random address. |
ble_hs_id_set_rnd | Sets the device's random address. |