Cross transport authentication

An authentication device for use with a portable media device, the authentication device comprising:

• a first connector configured to couple the authentication device to a portable media device, wherein the first connector comprises a first communication port;
• a second connector configured to couple the authentication device to an accessory, wherein the second connector comprises a second communication port;
• and
• a controller disposed in the first connector, the controller being configured to:
• detect connection of the portable media device to the authentication device;
• send a cross-transport request to the portable media device, the cross-transport request including (a) a request for authenticating the first communication port and granting a set of permissions to the first communication port and (b) a request to transfer a sub-set of permissions, from the set of permissions, to the second communication port;
• and
• receive an indication from portable media device that the sub-set of permissions was transferred to the second communication port.

A dongle comprising:

• a connector configured to connect to a first port of a portable media device, wherein an accessory is connected to a second port of the portable media device;
• a memory;
• and
• a controller disposed in the connector, wherein the controller is configured to:
• upon attachment of the dongle to the portable media device, send a first message to the portable media device inquiring whether the portable media device supports cross transport authentication;
• receive a second message from the portable media device indicating that the portable media device supports cross transport authentication;
• in response to the second message, send a third message to the portable media device, the third message including a request to authenticate the second port of the portable media device and a device identifier associated with the controller;
• communicate with the portable media device to authenticate the controller;
• and
• upon authentication of the controller, enter a low power state.