1. A computer-implemented method comprising: storing, in a digital wallet of a first user, item identification data that identifies a plurality of value-ascertainable items that are owned by the first user, wherein the plurality of value-ascertainable items includes a first value-ascertainable item; while storing the item identification data, receiving, over the network, exchange data that indicates a second value-ascertainable item is to be exchanged for the first value-ascertainable item, wherein the plurality of value-ascertainable items does not include the second value-ascertainable item; in response to receiving the exchange data, removing, from the item identification data, first item data that identifies the first value-ascertainable item and updating the item identification data to include second item data that identifies the second value-ascertainable item; wherein the method is performed by one or more computing devices.