CODEWITHSUNDEEP
androidencryptionbluetoothbluetooth-lowenergy
d3llafr33
d3llafr33

Reputation: 347

Clarification about LE encryption field used in the LL_FEATURE_REQ and LL_FEATURE_RSP

I sniffed with my Ubertooth One, some BLE packets between my Android phone and my BLE device, and I would like clarifications about a particular field and its meaning.

After the connection is established, a LL_FEATURE_REQ is sent with the value of the LE Encryption field set to 0 (false).

According to the offical documentation (BLUETOOTH SPECIFICATION Version 4.2 [Vol 6, Part B], 4.6 FEATURE SUPPORT):

"When this information is sent from a Controller to a Host, a bit set to 0 indicates that the Link Layer Feature is not supported in this Controller; a bit set to 1 indicates that the Link Layer Feature is supported in this Controller.

When this information is sent from a Controller to a peer Controller, a bit set to 0 indicates that the Link Layer Feature shall not be used by the Controllers; a bit set to 1 indicates that the Link Layer Feature may be used by the Controllers. "

Also in the LL_FEATURE_RSP the LL Encryption field is set to 0 (false).

So, according to this Message Sequence Chart (BLUETOOTH SPECIFICATION Version 4.2 [Vol 6, Part D]), before sending the LL_FEATURE_REQ, the Master device (my Android phone), first reads the supported features and then sends the request. enter image description here

Does this mean that my Android device does not support communication encryption?

EDIT:

Below is the Wireshark output (on the left is the the Bluetooth HCI snoop log from my Android phone, and on the right the packtet captured with my Ubertooth):

enter image description here

Upvotes: 0

Views: 1444

Answers (2)

d3llafr33
d3llafr33

Reputation: 347

After the last Wireshark update (Version 2.4.0 using on Windows), this problem seems to be fixed. Now the LL Encryption field is correctly set to 1 (true). Here is the same packet: enter image description here

Upvotes: 0

Emil
Emil

Reputation: 18482

If the LL_FEATURE_REQ contains a 0 for position of LE Encryption (position 0), then that device's controller does not support encryption. The LL_FEATURE_RSP contains the bitwise AND of the master's and the slave's supported features.

But it sounds strange that an Android device wouldn't support encryption...

Upvotes: 1

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