FrontLine BPA LOW ENERGY, Hardware User Manual

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Selecting Frame# 39,591 will display the Pairing Confirm from the initiator (Side 1) in the
Decoder
pane. The
Confirm Value shown is the Mconfirm 128-bit random number that contains TK, Pairing Request command,
Pairing Response command, initiating device address, and the responding device address. Selecting Frame#
39,600 would provide the Sconfirm random number from the responder (Side 2) with similar information
from that device but the random number would be different than Mconfirm.
Once pairing is complete and an encrypted session established, the keys are distributed by the master and
slave now identified by Side = M and Side = S respectively in the
Summary pane. In Frame# 39,661 the slave
has distributed LTK to the master to allow exchange of encrypted data. Frame# 39,661 through 39,714 in the
Summary pane SMP tab are the key distribution frames.
Figure 10 - SMP Pairing Confirm (Frame# 39,591) from Initiator (Side 1)
Figure 11 - SMP Key Distribution Frames
A.1.7.2.2 Link Layer
The Link Layer (LL) protocol manages the Bluetooth low energy radio transmissions and is involved in starting
link encryption. To observe the decoded LL commands, click on the
Frame Display LE LL
tab, search for
and select ControlPkt “LL_ENC_REQ”. This command should originate with Side 1, the initiator of the
encryption link. In Figure 11 Frame# 39,617 is selected in the Summary pane and we see the decoded LE LL
frame is display in the
Decoder
pane. Shown in this frame packet is the SKDm that is the Master Session Key
Diversifier (SKDmaster). In Frame# 39,623 you will find SKDslave that is combined with SKDmaster to create
the Session Key (SK). Both SDKs were created using the LTK. Frame# 39,635 through 39,649 in the
LE LL
tab
completes starting of the encryption process. After the slave sends LL_START_ENC_RSP (Frame# 36,649) the
Bluetooth devices can exchange encrypted data, and the ComProbe sniffing device can also receive and
decrypt the encrypted data because the appropriate “key” is provided in the
BPA 600 Datasource
window.
Figure 12 - LE LL Tab Encryption Request (Frame# 39,617) from Initiator (Side 1)
TELEDYNE LECROY Appendicies
201 Frontline BPA low energy Hardware & Software User Manual