Use hardware AES ECB encryption NRF52832 connect sdk

[LukeC]

I have AES ECB encryption working on the NRF5 system, but I cannot get it working on the Connect SDK.

I have found CONFIG_CRYPTO_NRF_ECB config, but this seems to require a different BLE controller.

I see an ecb.c file in the Nordic HAL in zephyr, but I need some help implementing using ncs.

/opt/nordic/ncs/v2.1.0/zephyr/subsys/bluetooth/controller/ll_sw/nordic/hal/nrf5/ecb.c

Any help or tips would be great, thanks!

[Einar Thorsrud]

Hi,

You can see an example of the use of AES ECB in the Crypto sample. You are right that this cannot be used together with some radio stacks though, as some use the ECB. In that case you have two options:

1. Use MSPL timeslots (see the MPSL timeslot sample). Within the timeslot, you will have access to most of the HW, including the ECB peripheral.
2. Do the ECB crypto operations in SW.

[LukeC]

Hello Einar, 

Maybe I am missing something, but I only see CBC, CTR, and CCM.  I believe all of these need the 52840 or 5340 and the ARM CryptoCell to have hardware acceleration. I was using the ECB since this is used with the BLE radio stack on the NRF52840 

[Einar Thorsrud]

Hi,

The documentation does not refer to ECB for some reason, but if you look at the example code (zephyr/samples/drivers/crypto/src/main.c) you will see it is demonstrated.

[LukeC]

It looks like I cannot enable the BT_CLR with the ECB hardware module. 

Am I setting something up incorrectly or is this just a limitation of the NCS/Zephyr SDK?

[Einar Thorsrud]

Ah, yes, I was not aware of that dependency. It is a limitation in NCS. You cannot use it while the SoftDevice Controller is active, but technically it should have been possible to get it to work using MPSL timeslots though it turns out that is currently not supported.

Do you have a strong need to do this in HW? If you only need to crypt small amount of data, or only do it rarely, then the downside of doing it in SW is often not significant.

[LukeC]

Yeah, I ran a software implementation and the cycle count is pretty minimal.  Probably not critical to run in hardware for my application.