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Bluetooth Encryption Not Being Decoded How to Decode Bluetooth Encrypted Data You will probably see that the last good frame captured was an LMP start_encrypt_req (Start Encryption Request) If this is the case, then FTS was missing some information that it needs to follow encryption. Bluetooth needs three pieces of information to process the encrypted data, The Bluetooth device addresses (BD_ADDR) of each device, the PIN (Personal Identification Number) code and a random number, generated by each device. The master and slave BD_ADDRs can be chosen from the lists above. To find out the BD_ADDRs of Bluetooth devices in the area, click on the "Discover Bluetooth Devices" button. The PIN code is a number that may be programmed in by the manufacturer, or entered by the user. In either case, it must be supplied to FTS for Bluetooth via the Set I/O screen, accessible from the Data Source window. If you have supplied the proper PIN and you are still having the same problem, then it is likely that FTS for Bluetooth did not capture the exchange of data involved in the generation of Link Keys, which occurs very early in the session (this is where FTS for Bluetooth learns the random number being used to generate the Link Key). Make sure that you start capture from the Control Window before you click the "Start Sniffing" button on the Data Source Window. In the Frame Display window, you should see a sequence similar to: LMP_in_rand LMP_accepted (LMP_in_rand) LMP_comb_key or LMP_unit_key This is the exchange of random numbers and keys that FTS for Bluetooth needs to see in order to decrypt the data. If you don't see this sequence, clear the buffer (click on the "eraser" icon) and try capturing again. Make sure that you click on "Start Capture" on the Control Window , and then "Start Sniffing" on the Data Source Window before the two Bluetooth devices start their connection.
A more detailed explanation of encryption in Bluetooth is attached below.
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