JP2012182641A - Distribution method for certificate invalidation list, transmission node used therefor, and relay node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distribution method for certificate invalidation list that effectively distributes a certificate invalidation list through vehicle-to-vehicle communication even under a highly dense environment of vehicles, and to provide a transmission node used therefor and relay node.SOLUTION: The transmission node codes a certificate invalidation list received from the authentication station using random network coding, and distributes coded data by broadcasting through vehicle-to-vehicle communication. The relay node recodes the received coded data for each fixed interval for broadcasting through vehicle-to-vehicle communication.

Description

  The present invention relates to a certificate revocation list distribution method for distributing a certificate revocation list by inter-vehicle communication, and a transmission node and a relay node used therefor.

  Various information such as vehicle location information is exchanged through the vehicle ad hoc network, and driving assistance such as alerting the driver is performed based on the collected information. If the information being exchanged is incorrect, the driver will be misguided.

  In encryption / authentication technology for ensuring the reliability of information, a key is used, and there is a model in which the key is trusted by a public key certificate issued by a trusted third party. Certificate validity verification is generally performed based on a certificate revocation list. If the certificate revocation list version update is slow, a certificate that has already been revoked may be erroneously valid. Therefore, the certificate revocation list needs to be distributed at high speed.

  Non-Patent Document 1 proposes a distribution method by inter-vehicle communication for distributing a certificate revocation list to a large number of vehicles as soon as possible by reducing the installation of costly roadside machines.

  One mechanism used for large-scale content distribution in network-connected computing environments such as vehicular ad hoc networks is a content distribution system using network coding. Patent Document 1 provides high-speed and scalable content distribution.

JP 2006-31693 A

K.P. Laberteaux, J.J.Haas, Y.-C. Hu, “Security Certificate Revocation List Distribution for VANET”, Proceedings of the Fifth ACM International Workshop on VehiculAr Inter-NETworking (VANET 2008), ACM, San Francisco, 2008.

  When a vehicle in a certain area becomes dense, in the methods of Non-Patent Document 1 and Patent Document 1, a packet including a certificate revocation list element or a packet encoding the element is transmitted from the vehicle at the same time. Packet collision increases and delivery performance deteriorates.

  In view of the above, it is an object of the present invention to enable a certificate revocation list to be distributed efficiently even in a high-density environment for vehicles.

  In order to achieve the above object, the invention according to claim 1 is characterized by a certificate revocation list distribution method for distributing a certificate revocation list transmitted from a transmission node by inter-vehicle communication using random network coding. Yes.

  The invention according to claim 2 is a transmission node used in the certificate revocation list distribution method according to claim 1, wherein the received certificate revocation list is encoded by random network encoding and encoded by road-to-vehicle communication. It is characterized by a transmission node that broadcasts data.

  The invention according to claim 3 is a relay station used in the certificate revocation list distribution method according to claim 1, wherein the relay node re-encodes and broadcasts the received encoded data at regular intervals. It is characterized by.

It is a figure which shows the relationship between each node of this invention. It is a figure which shows the flow of a process of the transmission node of this invention. It is a figure which shows the flow of a process of the relay node of this invention. It is a figure which shows the flow of a process of the receiving node of this invention. It is a figure which shows the simulation result of this invention.

  In this embodiment, certificate revocation lists are distributed by wireless multi-hop communication using network coding. In order to enable a vehicle to distribute certificate revocation lists efficiently even in a high-density environment, Distribute certificate revocation lists by inter-vehicle communication using random network coding.

  In a wireless network such as a vehicular ad hoc network, packet loss occurs due to collision of a plurality of packets. If a plurality of packets are network encoded into a single packet and transmitted, the number of packets propagating throughout the network is reduced. As a result, collisions are reduced and communication quality is improved.

  Network coding is a coding technique in which a plurality of data is coded into one data and relayed. The original data can be decoded from different encoded data sent from a plurality of paths.

  One implementation method of network coding is random network coding.

  In random network encoding, input data is encoded with a random encoding vector, and different encoded data is output each time. The encoded data can be further re-encoded without decoding. The original data can be decoded if the receiving node receives the same number of data as the input data together with the data re-encoded by the relay node as well as the data directly encoded by the transmitting node.

  The encoded vector is necessary for decoding. In order to eliminate the need for prior communication with a node to be decoded, it is a feature of random network coding that a coded vector and coded data are transmitted in a packet.

  The present embodiment is a broadcast communication system on a vehicular ad hoc network using random network coding for distributing a certificate revocation list transmitted from a transmission node such as a roadside machine.

  In the present embodiment, the transmission node (roadside machine) shown in FIG. 1 receives a certificate revocation list from the certificate authority by infrastructure communication. The received certificate revocation list is encoded N times by random network encoding, and N encoded data is broadcast by road-to-vehicle communication. The relay node re-encodes the received plurality of encoded data into one encoded data and relays it. If the receiving node receives the same N pieces of data as the transmitted encoded data, the receiving node decodes it.

  FIG. 2 shows a flow in which the sending node (roadside machine) encodes and sends a certificate revocation list. The sending node receives the certificate revocation list X from the certificate authority (S01). The received certificate revocation list X is divided into N pieces of data (S02). Since the received certificate revocation list is encoded N times with a random encoding vector, a variable for counting the current number of encodings is prepared (S03), and encoding is performed until the certificate revocation list is encoded N times. The transmission process is repeated (S04).

  In encoding, first, a random encoded vector C necessary for encoding is created (S05). The encoded vector C and the data X are encoded by performing a linear operation to generate encoded data y (S06). Since the encoded vector C is necessary for decoding, the encoded vector C and encoded data y are included in the packet and broadcast (S07). After broadcasting, the system waits for a certain time (S08), increments the number of encodings (S09), and then performs the next encoding / transmission process (S10).

  FIG. 3 shows the flow of a relay node that re-encodes received encoded data and broadcasts the encoded data. Since the relay node re-encodes and relays the received data at regular intervals, the re-encoding / relay process is repeated (S11).

Even if the received packet is smaller than the transmission data number N, re-encoding / relay processing is performed at regular intervals (S12). First, the encoded data y _i and the encoded vector D _i are extracted from the received packet p _i (S13). Since encoding is performed with a random encoding vector in re-encoding as well as encoding, an encoding vector C is created (S14). The encoded vector C and the encoded data y _i are linearly calculated and re-encoded (S15).

  Since the decoding requires the encoded vector D 'corresponding to the coefficient of X instead of the coefficient C of the encoded data Y, the encoded vector is updated. In order to update all N elements of the encoded vector, a variable indicating what number element of the encoded vector is updated is prepared (S16). The update process is repeated until all N elements of the encoded vector are updated (S17). The update of the i-th element of the encoding vector included in the matrix D including the encoding vector included in the received packet is performed by updating the i-th element of the encoding vector included in the matrix D including the encoding vector included in the reception packet. This is performed by linear calculation of the vector consisting of and the encoded vector C (S18). After updating the encoded vector, the update count is incremented (S19), and the process is repeated until the Nth element of the encoded vector D is updated (S20).

  When the update of the encoded vector is completed, the updated encoded vector D 'and the re-encoded data Z are included in the packet and broadcast (S21). After the re-encoding / relaying process, it waits for a certain time (S22), and the next re-encoding / relaying process is performed (S23).

FIG. 4 shows the flow of the receiving node that decodes the received encoded data. Since N pieces of encoded data are required for decoding, a variable for storing the current number of received packets is prepared (S24). The reception process is repeated until N packets are received (S25). In the reception process, first, reception waits until a packet broadcast by the transmission node / relay node arrives (S26). When the packet p _i is received (S27), the encoded data Z _i and the encoded vector D _i are extracted from the packet p _i (S28). After receiving the packet, the current number of received packets is incremented (S29), and the reception process is repeated until N packets are received (S30).

When N pieces of data necessary for decoding are received, decoding is performed. Since D included in the received packet is an encoded vector corresponding to a coefficient of X, a relational expression of Z = DX is established between the original data X and the received encoded vector D and encoded data Z (S31). D is a matrix composed of the encoded vector D _i included in the received packet. If an inverse matrix exists in this matrix, X = D ⁻¹ Z holds, and X is decoded from D and Z (S32).

  FIG. 5 shows a simulation result of the present embodiment (proposed method), unencoded inter-vehicle communication (flooding), and distribution only by road-to-vehicle communication using a plurality of roadside units.

  In a high-density environment, flooding causes a lot of packet loss, and it is possible to distribute a larger list than when only one roadside unit communicates with each other, but only four roadside units communicate with each other. The performance is not as good as the one delivered with This embodiment (proposed method) has higher delivery performance than flooding.

  This embodiment (proposed method), which relays and distributes data distributed by one roadside device by inter-vehicle communication, can distribute data with the same performance as distribution only by road-to-vehicle communication by 12 roadside devices. Since the number of machines can be reduced, the installation cost of roadside equipment can be reduced.

  In the embodiment described above, each step shown in FIGS. 2 to 4 is grasped as a means for realizing each function, and is specifically provided in the transmission node, the relay node, and the reception node. Executed by a computer.

Claims (3)

  A certificate revocation list distribution method, comprising: distributing a certificate revocation list transmitted from a transmission node by inter-vehicle communication using random network encoding.   A transmission node used in the certificate revocation list distribution method according to claim 1, wherein the received certificate revocation list is encoded by random network encoding and the encoded data is broadcast by road-to-vehicle communication. Sending node.   A relay node used in the certificate revocation list distribution method according to claim 1, wherein the relay node re-encodes the received encoded data and broadcasts at regular intervals.