CC2564: Start Encryption fails on re-connect with Connection Timeout

Tobias Heiss

Part Number: CC2564

Hello TI Team,

we are facing an issue re-connecting to a iPhone 11 using encrypted messages. Our device platform is a CC2564B with Bluetooth 4.0 support. Our device has the master role initiating an encrypted BLE connection to an iOS App running on iPhone 11 with iOS 13.3 Beta 2.

Initaial pairing process with an active connection works well.

Trying to re-connect to the mobile device fails with a Connection Timeout due to not receiving LL_ENC_RSP as you can see in the attached screenshot. HCI logs on iOS shows an Connection Terminated Due to MIC Failure (0x3D).

Attached you can find logs for Device HCI, Air and iPhone HCI logs:2019-11-14_iPhone11_iOS13_3_Beta_2_App4_7_10.zip

Questions:

Since the first connection works fine, what can go wrong with a re-connect?
Has this behavior been observed on other systems too?
Is there any other option to create an encrypted connection to work around this issue?

Best regards

Tobias Heiß

over 5 years ago

0 Tobias Heiss over 5 years ago

Intellectual 760 points

0 Hari Nagalla over 5 years ago in reply to Tobias Heiss

TI__Mastermind 27080 points

Which host MCU are you using? Is the Link key saved after first pairing/connection?

Thanks

0 Tobias Heiss over 5 years ago in reply to Hari Nagalla

Intellectual 760 points

Our host MCU is a TM4C129.

Yes we save the Link key.

0 Hari Nagalla over 5 years ago in reply to Tobias Heiss

TI__Mastermind 27080 points

From the traces, it looks like the master (CC2564B) did send the 'LL_ENC_REQ', but it did not receive 'LL_ENC_RSP' from the slave.

Is this problem seen only with iPhone? and a particular OS version? Did, you try with Android device?

Thanks

0 Tobias Heiss over 5 years ago in reply to Hari Nagalla

Intellectual 760 points

We see this problem only with iPhone 11. We tested nearly all iOS 13 Releses. An iPhone 7 Plus with iOS 13 works well.

The logs on iPhone seems to point on a MIC failure but I have no idea why.

We thought about LMP encryption key size (Bluetooth Expedited Errata Correction 11838) and I tested it with the newest Service Pack (CC256XB_BT_SP_v1.8) without success.

On Android devices we use BR/EDR so we have no issues there yet.

0 Hari Nagalla over 5 years ago in reply to Tobias Heiss

TI__Mastermind 27080 points

MIC failure, indicates message integrity check failure. We, are not sure why the iphone is reporting it, when the Ellysis sniffer has no issue.. To us, it seems like an issue on the iPhone side. The other option is to make it pair each time with legacy pairing needing no user passcode inputs.

Thanks