Hi, TomaszGrobelny:
To answer your questions:
1. If your main assembly is strong named, your satellite assemblies must be signed with the same private key. Check
here for more details.
2. I don't think it's possible for you to strong-name sign your assembly first and then let the end-user add satellite assembly for localiztion purpose. Since your private key is not published to the end-user, their localized satellite assemblies cannot be properly strong-name signed and thus cannot be used by the main assembly. But maybe you could consider Delay Signing an Assembly, which defers the actual signing until some later stage (typically just before shipping the assembly).
Here are some refs may help you:
1. Security and Localized Satellite Assemblies
http://msdn.microsoft.com/en-us/library/ff8dk041(VS.71).aspx 2. Delay Signing an Assembly
http://msdn.microsoft.com/en-us/library/aa719924(VS.71).aspx
Please mark the right answer at right time.
Thanks,
Sam