Authentication between seperate domains - Client/Server scenario

[Guest]

What is the best way to achieve authentication between two seperate non
trusting domains.

Scenario:
- i have a winform client application that resides on domain A
- the application makes calls to a web service on domain B
- the web service needs to be secured to limited users

Question: Domain B doesnt trust Domain A hence I can't use windows
integrated security. I am trying to avoid using a custom form for the user
name and password.

Is there any better way than this?

 

[Guest]

I feel custom login authentication on domain A will be an best option.