How to use CC310 ChaChaPoly with zero-length data or adata?

[Dirbaio]

Hello there,

It seems the CC310 backend for ChaChaPoly does not allow zero-length data or adata (associated data). I am implementing a protocol that requires this (Wireguard, based on the Noise-IK handshake),

I have tried removing the error checks in the nrf_crypto wrapper, but it seems the actual CC310 library also does checks.

Is there any way to get this to work?

Thanks

[Einar Thorsrud]

Hi,

I assume you are referring to the CRYS_CHACHA_POLY() function? You are right that this does not allow you to use zero data or adata. I have created an internal ticket so that this can be investigated. You should not expect any updates soon though, and it might not be possible.

[Dirbaio]

Yes, the issue is with CRYS_CHACHA_POLY.

It'd be great if this was supported. I understand that it's ARM IP (not Nordic) so that might make things more complicated...

Thanks! :)

[Dirbaio]

Hello! Any updates on this? As it stands now, this is a non-starter to use CC310 to implement WireGuard, because the protocol itself requires zero-length data and adata.

[Einar Thorsrud]

Hi,

It does not seem like it is supported yet, but I have bumped the internal feature request. You should probably not expect an update soon, though.