BL600
M
ODULE
Embedded Wireless Solutions Support Center:
http://ews-support.lairdtech.com
www.lairdtech.com/bluetooth
1
Americas: +1-800-492-2320
Europe: +44-1628-858-940
Hong Kong: +852 2923 0610
W
HISPER
M
ODE
Application Note
v1.0
I
NTRODUCTION
The goals of this document include the following:
To explain how to use Laird’s BL600 module in whisper mode pairing.
To test the Whisper Mode functionality through the use of a BT v4.0-enabled iOS device.
O
VERVIEW
Security is a critical issue in wireless communication. In Bluetooth Low Energy (BLE), when two devices wish
to communicate securely, Simple Secure Pairing is used. This process establishes a secret link key to correctly
authenticate devices. However, in most cases the pairing process itself is carried out on the same exposed
wireless medium and is therefore still vulnerable to interceptions and attacks.
To enhance security and ease during the pairing process, Laird developed a unique approach which involves
the transmission power being significantly decreased while pairing is in progress. This ensures that pairing is
not completed unless the devices are within a relatively close proximity to each other. This behavior is known
as Whisper Mode Pairing. This proximity-enhanced security adds the extra level of trust that can be used to
authenticate BLE devices. An additional benefit of Whisper Mode is that end users of products that are
implementing Laird’s BL600 can be certain they are connecting to the correct, intended remote device by
simply bringing them into close proximity. Finally, Laird’s whisper mode may decrease footprint and BOM
costs for OEMs by removing requirements for additional wireless technologies, such as Near Field
Communications (NFC); it provides similar attributes from within the BL600 module.
Whisper mode pairing is achieved with the function BleTxPwrWhilePairing(). This function, called once at
startup, sets the transmit power of all packets that are transmitted while pairing is in progress. Radial
measurements have shown that setting the pairing transmit power to -55 creates a ‘bubble’ with a radius of
about 30 cm, outside which pairing will not succeed. This should be decreased even further if the BL600 is
covered by the final product enclosures which affect the radio’s overall RF performance.
R
EQUIREMENTS
PC running Windows XP or later
UWTerminal 6.50 or later
Sample apps as deployed with the firmware’s zip file and specifically the application stored in the file
“htss.health.thermometer.sensor.SB”
USB A to mini B cable
BL600 devkit with firmware version 1.5.62.0 or later
iOS device with BT4.0 support (e.g. iPad 3/iPhone 4S/iPad mini or newer)
Internet connection on the iOS device (to download the BL600 app)
Note: This application note assumes that you are familiar with how to download
smart
BASIC applications
onto the BL600 using the UWTerminal utility. If not, refer to the module’s user guide and
specifically to the chapter “
Getting Started
”. You can access the BL600 user guide from the
Embedded Wireless Solutions Support Center:
https://laird-ews-support.desk.com/?b_id=1945#docs
