A hardware device interface supporting transaction authentication is described herein. At least some illustrative embodiments include a device, including an interconnect interface, and processing logic (coupled to the bus interface) that provides access to a plurality of functions of the device through the interconnect interface. A first transaction received by the device, and associated with a function of the plurality of functions, causes a request identifier within the first transaction to be assigned to the function. Access to the function is denied if a request identifier of a second transaction, subsequent to the first transaction, does not match the request identifier assigned to the function.