Check that points are multiplied by the cofactor when needed
Created by: claucece
As we are currently implementing the revision number 2 of the OTRv4 specification, we need to include a consistent way of safely using points.
Please, refer to the "Generating Shared Secrets" section of the OTRv4 spec.
- Check if the encoding function is actually multiplying by cofactor.
- Check if the decoding function is actually multiplying by cofactor.
Check, without leaking extra information about the value of
K_ecdhis the all-zero value and abort if so.