Using a '&' character within your password results in the following error:
>rskeymgmt.exe -a -f file.snk -p Strong&Password
Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
'Password' is not recognized as an internal or external command, operable program or batch file.
Is it me doing something wrong? Or is this a bug?