Patent ID: 7272858

Claim:
A method performed in combination with a host computer and a device that couples to and downloads an object from the host computer, the device performing symmetric decryption only and having a symmetric device key (DK) and a copy of (DK) encrypted according to a public key (PU) of an entity (PU(DK)), wherein the host computer has a public key and a private key, whereby the device receives a first object from the host computer at least a portion of which is symmetrically encrypted according to (DK), the method for communicating (DK) from the device to the host computer comprising: sending (PU(DK)) from the device to the host computer; sending (PU(DK)) and the public key of the host computer from the host computer to the entity, the entity having a private key (PR) corresponding to (PU), applying (PR) to (PU(DK)) to obtain (DK), and sending (DK) back to the host computer encrypted according to the public key of the host computer; and receiving (DK) encrypted according to the public key of the host computer from the entity at the host computer, applying by the host computer the private key thereof to (DK) encrypted according to the public key of the host computer to obtain (DK), whereby the host computer symmetrically encrypts the first object according to (DK) and downloads the encrypted first object to the device, and the device symmetrically decrypts the encrypted first object based on (DK).