BLE mode 1 level 2 with just works. Implementing SHA256 hash algorithm.

[Bloq]

Hello,

I am working on a nRF52840 and started with the SDK15 gls bonding example.  The device has no buttons or display so we are stuck with 1v2.  We are hoping to incorporate a SHA256 hash algorithm that all of our characteristics run through before being sent over ble.  I have found the nRF_crypto_hash library that uses an init, update, finalize or just calculate with the necessary info and references.  I am having trouble finding an example that basically replaces the use of ECDH key generation with a SHA256 hash algorithm.  I am currently using the peer manager and when I experimented with MITM it was handling all of the encryption with for bonding.  If someone could point me in the right direction or give me some next steps that would be great,

Thank you,

Bloq

[Bloq]

To clarify the question I do not want to modify the peer manager.  I believe the majority of the work is going to be hashing all of the characteristics before sending them out over Bluetooth.  This is where I am not sure how to proceed and would appreciate some examples.

[Vidar Berg]

Hello,

I would recommend reading through this blog post by Daniel if you are looking to add an additional layer of security in your application: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/intro-to-application-level-security-using-the-ecb-.  But I'm not sure I understand how you are going to use hashing to increase security?

I am having trouble finding an example that basically replaces the use of ECDH key generation with a SHA256 hash algorithm.

The pairing procedures are clearly defined by Bluetooth specification, so this is not something you can change and still remain Bluetooth compatible.

Best regards,

Vidar