Use the xsd.exe to first generate an XSD and then use the same exe to generate class files. More info - http://msdn.microsoft.com/en-us/library/x6c1kb0s.aspx.
Saved your xml as security.xml on my system and ran the following commands in visual studio command prompt:
xsd Security.xml
The step above generated two xsd files which can be used to generate class.
xsd Security.xsd Security_app1.xsd /classes