A virtual machine comprises a unique identifier that is associated with one or more encryption keys. A management server encrypts the virtual machine's virtual hard disk(s) using the one or more associated encryption keys. The management server further provides the one or more encryption keys to a limited number of one or more servers in a system. Only those one or more servers that have been provided the one or more encryption keys can be used to load, access, and/or operate the virtual machine. The management server can thus differentiate which virtual machines can be operated on which servers by differentiating which servers can receive which encryption keys. In one implementation, a management server encrypts all virtual machines in the system, but encrypts virtual machines with sensitive data with a limited set of encryption keys, and further provides those encryption keys to a limited set of trusted servers.