If you like to keep solutions organized, keep common things together, store keys separately, and use automated builds you’d probably get frustrated by the new Signing tab of the Project Settings UI. Don’t get lured by the fancy look-n-feel of this dialog – it won’t let you set relative path of the strong key file. If you browse to the existing file, IDE will try to copy it into the project folder. Type things like “..\key.snk” and it just barks at you that such symbols are not allowed in the file name. It's odd, as this is very important when you manage and store keys separately and use them to sign multiple projects. This is vital in BizTalk development, when all bindings and mappings depend on strong names of artifacts and accidental change of signature can cause solution to break.
The hack is simple: open project file *.csproj or *.vbproj in notepad and find element <AssemblyOriginatorKeyFile>. Type in path of your choice something like: “..\..\Common\KeyFileName.snk..”, save and reload the project. You're set to run your favorite build script.