A vehicular security network device, comprising: a plurality of conduits , each configured to connect a respective security zone to an external network, each respective security zone including a respective plurality of functional elements (F11-F33) having a same risk level assessed based on a vehicular security risk assessment matrix; wherein a first one of the security zones is a subzone of a second one of the security zones having a risk level lower than the risk level corresponding to the first one of the security zones , and gate keepers disposed on respective ones of the conduits and configured to control an access to the plurality of functional elements (F11-F33) in the respective security zone that the conduit connects to the external network, the gate keepers being designed to provide respective different security levels corresponding to the risk levels of the security zones that are connected to the external network by the conduits on which the gate keepers are disposed, wherein a first one of the gate keepers is designed to provide a risk level higher than or equal to a predetermined level, and includes a plurality of independent security elements, at least one of the independent security elements being embodied by a hardware-based security element using an authentication key held by a physical unclonable function (PUF); wherein a second one of the gate keepers that is disposed on a second one of the conduits, located between the second one of the security zones and the external network, is configured to control an access to the second security zone , the second one of the gate keepers including a hardware-based security element that obtains a lower security level than the first one of the gate keepers . a plurality of conduits , each configured to connect a respective security zone to an external network, each respective security zone including a respective plurality of functional elements (F11-F33) having a same risk level assessed based on a vehicular security risk assessment matrix; wherein a first one of the security zones is a subzone of a second one of the security zones having a risk level lower than the risk level corresponding to the first one of the security zones , and gate keepers disposed on respective ones of the conduits and configured to control an access to the plurality of functional elements (F11-F33) in the respective security zone that the conduit connects to the external network, the gate keepers being designed to provide respective different security levels corresponding to the risk levels of the security zones that are connected to the external network by the conduits on which the gate keepers are disposed, wherein a first one of the gate keepers is designed to provide a risk level higher than or equal to a predetermined level, and includes a plurality of independent security elements, at least one of the independent security elements being embodied by a hardware-based security element using an authentication key held by a physical unclonable function (PUF); wherein a second one of the gate keepers that is disposed on a second one of the conduits, located between the second one of the security zones and the external network, is configured to control an access to the second security zone , the second one of the gate keepers including a hardware-based security element that obtains a lower security level than the first one of the gate keepers . <EOS>