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Pairing and Bonding

System User Guide

289

Appendix G Pairing and Bonding

Motivation

Many of the services offered over wireless communication such as Bluetooth

and Z-Wave

can expose

private data or allow the connecting party to control the involved devices.

For security and reliability reasons it is necessary to be able to recognize specific devices and thus enable

control over which devices are allowed to connect to a given device.

To resolve this conflict wireless communication systems like Bluetooth

and Z-Wave

uses a process called

bonding, and a bond is created through a process called pairing.

The pairing process is triggered either by a specific request from a user to create a bond (for example, the

user explicitly requests to “Add a Z-Wave

device”), or it is triggered automatically when connecting to a

service where (for the first time) the identity of a device is required for security purposes. These two cases are

referred to as dedicated bonding and general bonding respectively.

Pairing often involves some level of user interaction; this user interaction is the basis for confirming the

identity of the devices. Once pairing successfully completes, a bond will have been formed between the two

devices, enabling those two devices to connect to each other in the future without requiring the pairing

process in order to confirm the identity of the devices.

When desired, the bonding relationship can later be removed by the user.

Implementation

During the pairing process, the two devices involved establish a relationship by creating a shared secret

known as a link key. If a link key is stored by both devices they are said to be paired or bonded.

A device that wants to communicate only with a bonded device can cryptographically authenticate the

identity of the other device, and so be sure that it is the same device it previously paired with. Once a link key

has been generated, an authenticated Asynchronous Connection-Less (ACL) link between the devices may

be encrypted so that the data that they exchange over the airwaves is protected against snooping.

Link keys can be deleted at any time by either device. If done by either device this will implicitly remove the

bonding between the devices; so it is possible for one of the devices to have a link key stored but not be

aware that it is no longer bonded to the device associated with the given link key.

Wireless services generally require either encryption or authentication, and as such require pairing before

they allow a remote device to use the given service. Some services, such as the Object Push Profile, elect not

to explicitly require authentication or encryption so that pairing does not interfere with the user experience

associated with the service use-cases.

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Essence We.R Guia do Utilizador Página 289