Enterprise Library 4.0 has been released and the Strong Naming Guidance Application Block has been removed from the EntLib, but it is available as a separate download in entlibcontrib:
The direct link is here:
https://www.codeplex.com/entlibcontrib/SourceControl/DownloadSourceCode.aspx?changeSetId=18160 (Note that this is not a stable release)
If you are too lazy busy to download, open VS and compile you can download here the msi.