A method and an apparatus for using an encrypted unique digital signature ("engraved signature") as a uniquely definable signature to control the use or execution of software in a computer system. The computer system has a Network Interface Card ("NIC") with a Media Access Control ("MAC") address. On start up, the engraved signature is retrieved from the persistent storage medium of the computer system and the MAC address is retrieved from the NIC. A computed encrypted signature is generated using the MAC address. Where the computed encrypted signature does not match the engraved signature, the execution of the software is halted.