A method for providing centralized user authorization to allow secure sign-on to a computer system is disclosed. In response to a user attempting to boot up a computer system, a message is sent to a trusted server by a hypervisor within the computer to request a new hard drive password for the computer system. If the user is not authorized to access the computer system, a packet is sent by the trusted server to instruct the hypervisor to stop any boot process on the computer system. If the user is authorized to access the computer system, a packet containing a partial hard drive password is sent by the trusted server to the computer system. The packet is then encrypted with a system public key by the computer system to yield the partial hard drive password. The computer system subsequently combines the partial hard drive password with a user password to generate a new complete hard drive password to continue with the boot process.