Upgrade to BLE Spec 4.2 with new softdevice

RE: Upgrade to BLE Spec 4.2 with new softdevice

endnode — Thu, 28 May 2015 19:01:06 GMT

I was not aware about these. Still not sure if key exchange part is OK with up to 1 second delay but if so then great. Let's see if it will get implemented in the SD one day (or probably better if it will be available on nRF52).

RE: Upgrade to BLE Spec 4.2 with new softdevice

atummac — Thu, 28 May 2015 16:35:44 GMT

I am not sure it would be prohibitively slow. There are open libraries (github.com/.../micro-ecc) to do ECDH even on 8-bit microcontrollers and the performance numbers they are giving are in the 0.5 - 4 second range (this is the key exchange part, which should not be happening often) on an 8-bit 16MHz AVR. As far as I understand, once the key is established (LTK), using it to encrypt/decrypt data would be no different than the LTK established using "JustWorks or 6-digit" methods. I have a feeling the nRF51822 could go quite a bit faster than the AVR if it has single cycle 32-bit multiplies (not all Cortex-M0s do according to ARM's website).

RE: Upgrade to BLE Spec 4.2 with new softdevice

Ulrich Myhre — Thu, 28 May 2015 10:42:33 GMT

It would be quite slow, but it is not outside the realm of possibility. Since key generation happens seldom, it could be done with little impact for applications with longer connections.

RE: Upgrade to BLE Spec 4.2 with new softdevice

endnode — Thu, 28 May 2015 10:13:14 GMT

Well I guess it's safe to say there will be no ECC on nRF51 because there is no dedicated HW block and doing ECDH in SW on ARM Cortex-M0 in real time is pretty much no go.

RE: Upgrade to BLE Spec 4.2 with new softdevice

atummac — Wed, 27 May 2015 17:29:09 GMT

Thank you for your answer!

RE: Upgrade to BLE Spec 4.2 with new softdevice

Ulrich Myhre — Wed, 27 May 2015 16:38:37 GMT

It is not mandatory to support all the features in the new specs to claim compliance, so if you are interested in a particular feature you should refer to that one specifically. Our S130 SoftDevice is 4.2 compliant, but do not support LE Secure Connections as of today. S110 8.0.0 is compliant to 4.1 as you mention, but only implement the Privacy 1.1, low duty-cycle directed advertisement and concurrent broadcaster features.

For future advances and timelines, you would have to contact a sales representative. Requests to those teams help developers focus on the right features at the right time. If you do not know your local sales representative, shoot me a message with your location and I will provide you with the contact information.