Hi Joep,
>> My Nettalk version = 11.45
ok, that's pretty old, but I'll try and answer usefully
>> And when I say Public key I mean my Cert file.
ok, so you're a server right?
By "cert" file you mean a CRT file?
I'm not sure what you mean by "giving that to them"...
That's not a thing - as in I've never needed to give a CRT file to anyone..
(which probably explains why I'm completely lost here...)
>> So I have a webservice which has to communicate with an Api Gateway.
What's an API gateway? And you'd communicate with that to do what? Are you making API requests of your own? To some other server?
>> The administrator of the gateway asked me for the Csr file.
>> He said he would sign it and sended me this p7b ,based on the csr, file back for my use.
Ok, so I guess you need to be a lot more explicit as to what an API Gateway is, what it's doing, what it needs and so on.
I can't really give you advice because I guess I'm not sure what an API gateway is, why you need to communicate with it, or what it needs...
You may need to fill in a lot more detail mate - sorry.
Cheers
Bruce