1. A method of providing a security service in a virtualized computer system, comprising: providing a security service application in a first operating system running in a first partition of a virtualized computer system; receiving a request from an application program for a security service, wherein the application program is running in a second operating system in a second partition of the virtualized computer system, the first partition being separate from the second partition; providing, by the security service application in the first partition, the security service in response to receiving the request from the application program, wherein the first partition is configured to certify the results of the security service performed by the security application program in the first partition using a trusted key that uniquely identifies the first partition.