CC2564C: iPhone Rejecting Secure-connection

Vishnuprasad V1

Intellectual 560 points

Part Number: CC2564C

Hi TI,

We are using CC2564C chip for our BT-BLE-based Infotainment system.

As we want to maintain the BT and BLE connection to one device. We use secure pairing for this.

The secure pairing of BLE as a process works fine with CC2564C, we are able to use that without any struggles.

The issue starts when we have to change the MAC-ID of the CC2564C.

As part of Production, We wanted a custom MAC_ID tied to the Serial Number.

So we used VS_Set_Bluetooth_Address() function. Now the MAC-ID of BT and BLE changes.

Now if we do SecurePairing with iPhone, iPhone rejects the connection.

We are using Static BD-Address, same address for BT and BLE.

What is the Reason this is failing? Is it because the Identity Address on the secure Pairing of BLE is not getting changed?

What we can do to change the Identity address of the CC2564C?

Thanks!

Vishnuprasad V

over 3 years ago

0 Daniel Olis over 3 years ago

TI__Intellectual 1155 points

Hi Vishnuprasad,

Please clarify here: are you secure pairing then changing the MAC Address? If so, the secure pairing process/bonding should only be initiated after the MAC Address has already been changed. If not, sniffer logs may be helpful to identify the issue here.

Also, VS_Set_Bluetooth_Address is the correct function to change the MAC Address/Bluetooth Address.

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

We are doing the MAC Address change first. Then only initiating the pairing.

Thanks!

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

Please find the attached HCI Snoop logs.

iphone_SecurePairing_logs.zip

Thanks!

0 Daniel Olis over 3 years ago in reply to Vishnuprasad V1

TI__Intellectual 1155 points

Hi Vishnuprasad,

Please allow me some time to look at these logs. That said when I said sniffer logs I was not referring to HCI logs, I was referring to logs that capture the over the air packets. Regardless I will see if I can glean something from the HCI logs that can point us in the right direction.

Regards,

Daniel

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

Can this happen because we are not using Random Addresses?

Or because the ID address of the chip is not getting changed?

Thanks!

0 Daniel Olis over 3 years ago in reply to Vishnuprasad V1

TI__Intellectual 1155 points

Hi Vishnuprasad,

According to the logs the BD_ADDR is successfully being changed when you issue the command. That being said, the HCI_Disconnect is being sent with reason (0x13) meaning the remote device is terminating the connection. Without sniffer logs it would be difficult to determine why the remote device is requesting the disconnect.

Regards,

Daniel

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

I think the issue is happening in the CC2564C side.

I am getting the error trigger on the CC2564C side with "GAP_LE_PAIRING_STATUS_DHKEY_CHECK_FAILED".

Analyzing the iPhone logs, We also see that the iPhone has sent the DHkey to CC2564C, somewhere verification of the DHkey failed.

Does this error give you any Idea?

We will try to get the sniffer logs also for these. I doubt whether we can sniff that part as that is a security mechanism.

Meantime if you can make out something from the "GAP_LE_PAIRING_STATUS_DHKEY_CHECK_FAILED" indication. Please let us know.

Thanks!

0 Daniel Olis over 3 years ago in reply to Vishnuprasad V1

TI__Intellectual 1155 points

Hi Vishnuprasad, I'm not sure why the DHKey would fail unless its no longer valid for some reason.

I will say another difference I noticed in the HCI logs is that at the point where the HCI disconnect happens in the failure log (Trace 7126) in the passing log (Trace 6146) there is a BLE_encryption_req from the remote device, this most likely coincides with whenever the DHKey is being sent but we'd have more insight with sniffer logs.

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

Can you check from this thread?

https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/1219366/cc2642r-dh-key-check-fail-in-pairing

Even though it is a different chipset, I think the Behaviour is similar. The details of that issue are exchanged over mail, so I have no clear idea on the fix.

can you please try to get that details?

Thanks!

0 Daniel Olis over 3 years ago in reply to Vishnuprasad V1

TI__Intellectual 1155 points

Hi Vishnuprasad,

I will try and reach out to the TI employees in the thread.

Regards,

Daniel

0 Daniel Olis over 3 years ago in reply to Daniel Olis

TI__Intellectual 1155 points

Hi Vishnuprasad,

I was able to get a hold of one of the involved TI Employees involved with the thread you linked. It has already been handed off to another team within TI because it concerns an automotive customer and its resolution is unknown on my end. However, speaking with the initial Apps Engineer, it seems their failure trigger is different, disconnecting one phone after trying to pair with a second phone causes the error on their end.

I can send you the sniffer log they captured over E2E direct message if you like but I do not think that continuing to dig into their issue would necessarily help yours.

Regards,

Daniel

0 Vishnuprasad V1 over 3 years ago in reply to Daniel Olis

Intellectual 560 points

Hi Daniel,

Thanks for your efforts. When we debugged from our side we were able to make the connection when we used ST crypto Library for generating the DHkey.

This is still under test. The DH key generation and validation part seems to have some issues when we change the mac-address.

If you can check on the DH key part and get this answered with your API itself great.

Else you can consider this thread as closed.

Thanks!

0 Daniel Olis over 3 years ago in reply to Vishnuprasad V1

TI__Intellectual 1155 points

Hi Vishnuprasad,

I'll look into it on our end but glad you were able to solve the issue. Thank you for the valuable feedback.

Regards,

Daniel

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CC2564C: iPhone Rejecting Secure-connection