Identify StrongName from Assembly PublicKey?

I'm looking to update some code to remove the old CAS functionality and instead stand up an AppDomain using the newer sandbox configuration.  My problem is I'm trying to determine the StrongNames for a couple of assemblies for which all I have is the PublicKey as a magic string.  The StrongNames are required for the newer v2 APIs for granting full trust in the sandbox AppDomain

Basically I have 

new StrongNameMembershipCriteria(new StrongNamePublicKeyBlob("MagicStringHere"), null, null), new PolicyStatement(permisisonSet)));

Is there a way to identify the StrongName from the MagicString?  I was looking at the sn.exe utility, but unless I'm missing something this will output the Assembly's PublicKey and PublicKeyToken not the other way around.