1. A communications network-node circuit, comprising: a storage device; a receiver configured to receive a local digital certificate list published by a helper-node statically positioned within a geographic area, wherein the helper-node maintains the local digital certificate list based on end-nodes entering the geographic area and publishes the local digital certificate list in response to detecting a predetermined number of changes to the local digital certificate list based on the end-nodes entering the geographic area; a digital certificate validity list circuit configured to download and, subsequently, to store in the storage device, a first set of digital certificates corresponding to a first set of network-node devices, having a first set of geographic and device performance attributes, wherein the first set of digital certificates are based on the local digital certificate list; a second set of digital certificates corresponding to a second set of network-node devices, having a second set of geographic and performance attributes; and a digital certificate validity list including the first set of digital certificates and the second set of digital certificates; and wherein the communications network-node circuit includes circuits configured to, filter the digital certificate validity list based on a range of geographic and device performance attributes; and transmit the filtered digital certificate validity list to the first set of network-node devices if the first set of geographic and device performance attributes are within the range, wherein the first set of network-node devices download and store in memory the filtered digital certificate validity list and use the filtered digital certificate validity list to verify digital certificate invalidity; and transmit the digital certificate validity list to the second set of network-node devices if the second set of geographic and device performance attributes are within the range, wherein the second set of network-node devices download and store in memory the digital certificate validity list, and wherein the first set of network-node devices and the second set of network-node devices are end-node devices.