Patent ID: 6782477
Filing Date: 2004-08-24
Classification: G06F

Abstract:
A method of operating a system, comprising the steps of:reading a portion of software code from a storage device in the system, wherein the portion of software code has been digitally signed with a first key prior to entering the system; sending the portion of the software code to a cryptography unit contained in a tamperproof circuit associated with the system; decrypting a signature file corresponding to the portion of the software code with the cryptography unit using a second key stored in the tamperproof circuit to form a decrypted signature file; determining whether the portion of the software code is valid by using the decrypted signature file; preventing operation of the system if the portion of the software code is not valid; receiving a third key from a server across a network; reading a portion of encrypted code from the storage device; and decrypting the portion of the encrypted code with the cryptography unit using the third key.