Terminology » Bluetooth address types and subtypes

Bluetooth address types and subtypes

bluetooth device address iot ble bluetooth low energy

Introduction : Bluetooth devices use unique addresses for identification, which can be public or random. Random addresses further split into static and private types, each offering different levels of security and privacy.

In Bluetooth Low Energy (BLE), every device has a Bluetooth Device Address which is a 48 bit value used to identify it at the Link Layer. BLE supports different address types to balance permanent identification, privacy and security.

1. Public Device Address

  • Definition: A unique, permanent 48-bit address assigned by the IEEE, similar to a MAC address in Wi-Fi. This is fixed address and does not change as it is factory programmed. It must be registered with IEEE similar to wi-fi and ethernet mac addresses.

    Format:

  • 24 bits: Company Identifier (Organizationally Unique Identifier, OUI)

  • 24 bits: Device Identifier

  • Bit 46–45 of the address are 00 (indicating “public”).

2. Random Device Address

BLE also supports random addresses, which can be static or private.

2.1 Static Random Address

  • Definition: Randomly generated once (e.g., at manufacturing or first boot) and stored in non volatile memory. It can not change until a power cycle.
  • Persistence: Remains the same until manually regenerated or device reset to factory settings.

2.2 Private Random Address

Used for privacy features; changes periodically to prevent tracking.

(a.) Non Resolvable Private Address (NRPA)

  • Definition: Randomly generated and changes frequently.
  • Resolvable? No, it means cannot be linked to previous addresses.
  • Not commonly used.

(b.) Resolvable Private Address (RPA)

  • Definition: Random address that changes periodically but can be resolved by bonded devices using the Identity Resolving Key (IRK).
  • Usage: Common in paired devices to protect privacy while still allowing automatic reconnection.

Conclusion: Understanding Bluetooth address types helps in designing devices that balance traceability, security, and energy efficiency. Selecting the right address strategy can protect user privacy without compromising connectivity.