A system and method for authenticating an operating system includes, in accordance with one aspect, a method in a computer system having a processor, an operating system (OS), and a software identity register that holds an identity of the operating system, the processor having a private key. The method comprises forming an OS certificate containing the identity from the software identity register and signing the OS certificate using the private key. In accordance with another aspect, the signed identity is submitted to a recipient to prove an identity of the operating system to the recipient.