Signing a existing .NET assembly

I could'nt find any support for signing a unsigned .NET assembly in .NET Framework 2.0 SDK.  Provided I have the source code and option to rebuild the assembly, I can sign it in the process of assembly generation. Thankfully ILMerge tool came for the rescue. It can be downloaded from

https://www.microsoft.com/downloads/details.aspx?familyid=22914587-b4ad-4eae-87cf-b14ae6a939b0\&displaylang=en

Command to sign: ilmerge weak.dll /keyfile:key.snk /out:strong.dll