crypto backend for ble secure dfu bootloader(pca10056/nRF52840 DK)

[B.Ho]

Hi, there~

Currently, I'm working on nRF52840 DK with  BLE Secure DFU Bootloader.

I have done the dfu with nRF Connect APP successfully.

But I have a question about the nrf_crypto backend module.

The SDK document states that micro-ecc needs to be installed as the backend before test the BLE Secure DFU Bootloader.

But I found that the cc310 backend which seems to be used as crypto backend is included in the example. 

I skipped the micro-ecc installation step and it had no problem to run the dfu.

I do not know much about the cryptography process.

My question is

1. Is micro-ecc needed for BLE Secure DFU Bootloader?

2. Any document I need to get through before all of this?

development environment:

OS: windows 10

IDE: SES

SDK: nRF5_SDK_15.3.0_59ac345

SD: s140_6.1.1

Board: nRF52840 DK

Thanks~~

[Einar Thorsrud]

Hi,

1. This is just outdated documentation. Where did you see it? The bootloader can use CC310 instead of micro-ecc starting with SDK 15.0.0, so there is no need to actually use micro-ecc. 

2. Well, DFU is quite complex which is why we have a lot of documentation for it. But since you got it working I assume you have most of what you need allready. What documentation did you have in mind?

[B.Ho]

Hi, Einar~

Thanks for the reply.

1. I downloaded the sdk document zip file from the nordic website, document library->sdk document. The version is v15.3.0. The statement about installing micro-ecc is included in the ble secure dfu bootloader test phase.

2. Well, I think I do not know what the crypto backend really is. It will be great for me if I can get a guidance to understand the basic concept of cryptography process.

Thanks again~~

[Einar Thorsrud]

Hi,

1. Then that is a remedy of older SDK's. There was a limitation of how the code is organized so you needed micro-ecc for building even though it was not actually used, but that is not the case for the bootloader in SDK 15.3.

2. Essentially nrf_crypto is a library that provides the same unified API for underlying crypto libraries (such as mbed TLS, micro-ecc, CC310 etc.). The backend represents the actual crypto library (such as micro-ecc). You can refer to the nrf_crypto documentation for details.

Br,

Einar