An apparatus (Mon) located at the tile-to-network-on-chip interconnect of a tile in a tiled data processing architecture comprising a plurality of tiles, each provided with an apparatus (Mon) as claimed located at the tile-to-network-on-chip interconnect of the tile, wherein each tile is any combination of computing and/or storage resources that are located at the same logical position in the on-chip interconnect; and wherein the apparatus comprises- an interface with its associated tile, for receiving access requests to resources of remote tiles therefrom and for forwarding checked requests of remote tiles thereto; and a hardware capability-enforcement unit with a set of registers, including at least one capability register (i) and an ID register, wherein the or each capability register stores a capability (c) to a remote tile resource and an authentication token (auth), and wherein the ID register stores a unique identifier of a subsystem (A, B) controlling the associated tile; and wherein the apparatus is configured to-on receiving an access request, check the request against the capability (c), and send the request as a checked request including the authentication token (auth) to the remote apparatus associated with the remote tile having the requested resource (step 3a); and on receiving a checked request from a remote apparatus, compare the authentication token therein with the unique identifier (step 4), and on a successful comparison, allow access to the resource (step 5a). wherein each tile is any combination of computing and/or storage resources that are located at the same logical position in the on-chip interconnect; and wherein the apparatus comprises- an interface with its associated tile, for receiving access requests to resources of remote tiles therefrom and for forwarding checked requests of remote tiles thereto; and a hardware capability-enforcement unit with a set of registers, including at least one capability register (i) and an ID register, wherein the or each capability register stores a capability (c) to a remote tile resource and an authentication token (auth), and wherein the ID register stores a unique identifier of a subsystem (A, B) controlling the associated tile; and an interface with its associated tile, for receiving access requests to resources of remote tiles therefrom and for forwarding checked requests of remote tiles thereto; and a hardware capability-enforcement unit with a set of registers, including at least one capability register (i) and an ID register, wherein the or each capability register stores a capability (c) to a remote tile resource and an authentication token (auth), and wherein the ID register stores a unique identifier of a subsystem (A, B) controlling the associated tile; and wherein the apparatus is configured to-on receiving an access request, check the request against the capability (c), and send the request as a checked request including the authentication token (auth) to the remote apparatus associated with the remote tile having the requested resource (step 3a); and check the request against the capability (c), and send the request as a checked request including the authentication token (auth) to the remote apparatus associated with the remote tile having the requested resource (step 3a); and on receiving a checked request from a remote apparatus, compare the authentication token therein with the unique identifier (step 4), and on a successful comparison, allow access to the resource (step 5a). compare the authentication token therein with the unique identifier (step 4), and on a successful comparison, allow access to the resource (step 5a).