The only tricky part is PROV_RSA_FULL -> PROV_RSA_AES, otherwise SHA-256
is not recognized as a valid algo. MSDN documentation for PROV_RSA_FULL
at
<https://msdn.microsoft.com/en-us/library/windows/desktop/aa387448%28v=vs.85%29.aspx>
and PROV_RSA_AES at
<https://msdn.microsoft.com/en-us/library/windows/desktop/aa387447%28v=vs.85%29.aspx>
say that AES is a superset of full, so should be no
backwards-compatibility issue. I tested this on Windows 7, but according
to the documentation, it should be no problem on Windows XP, either --
provided that the latest SP is installed.

Change-Id: I3ae196679c2cbf0e9e55fab10584d9c46a480659