topic Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present in NFC

BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

zeelivermorium — Thu, 19 Mar 2020 20:50:07 GMT

As the picture suggests, the NDEF bluetooth carrier configuration record contains these 3 fiels:

Security Manager TK Value, Secure Connection Confirmation Value and Secure Connnection Random Value. But TK value should be used in legacy pairing while the other two are used in secure pairing and you cannot use 2 pairing at once. Does anyone know why all three fields are included all at once? Shouldn't just choose what to inbcluded accordingly? Even the LE Example NDEF data has all three fields present in the payload.

Thanks for your time and help in advance!

Best,

Zee

Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

stephanie_m — Mon, 23 Mar 2020 19:23:27 GMT

Hello,

Do you mean an OOB paring ? Sorry, the question is not that clear, which device are you using ? and which is the problem you are having ?

Could you please check the following links?

UM11118

NFC active pairing for audio devices

https://community.nxp.com/docs/DOC-335241

Regards,
Estephania

Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

zeelivermorium — Sun, 29 Mar 2020 08:31:56 GMT

Hello,

This is OOB pairing and I took the pic from BTSSP document. As I said in the description, BLE legacy pairing and Secure Connection pairing cannot be used at the same time. Why the BTSSP payload include them at the same time? This kinda requires knowledge from both NFC and BLE, not just NFC or just BLE. And I couldn't find a reason why this is the case by searching through google or any other documentation I can find.

Best,

Zee

Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

stephanie_m — Mon, 30 Mar 2020 22:12:02 GMT

Hello,

Sorry you did not answer any of my questions.

Please, check the following link

Hope this helps.

Regards,

Estephania

Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

zeelivermorium — Mon, 30 Mar 2020 23:56:18 GMT

Hi,

I did answer all your questions ("This is OOB pairing" as first 4 words and describe the question again though I know it could be a bit confusing) except the device, since this is not device exclusive this is about the BTSSP overall. I am using NXP devices (PN532, NTAG I2C Plus and PN7150), if I am not I will not show up here and waste your time. I did check all the links, and I have read all of them before posting. But NONE of then examples show the use the sc confirm value, sc random value or sm tk value. My question is not about making a successful OOB pairing, which I have already done by onlying including device address, role and local name.

You can see very clearly, since I have underlined it this time.

And according to bluetooth core spec:

Security Manager TK Value is for BLE legacy pairing to calculate the STK.

------------------------------------------------------------------------------------

Secure Connection Confirm Value is used for BLE secure pairing.

Secure Connection Random Value is used for BLE secure pairing.

Legacy pairing and secure pairing cannot be used at the same time, why do the BTSSP shows examples of them presenting at the same time?

It sounds contradicting to the bluetooth spec.

Thanks for your time to answer my question.

Best,

Zee

Re: BTSSP: SM TK Value, SC Confirm Value and SC Random Value All Present

stephanie_m — Thu, 02 Apr 2020 00:20:45 GMT

Hello,

Just consider that when pairing you do not know the capabilities of security that the other device has, it can be either with the legacy or the secure connection.

Regards,

Estephania