CN105871831A - Data fragmenting and downloading service method in vehicular network - Google Patents

Abstract

The invention discloses a data segment download service method in a vehicle network, relates to the field of vehicle network communication security, in particular to a data segment download service method based on RSU security and privacy protection in a vehicle network, specifically comprising the following steps: System initialization; request for anonymous navigation certificate; obtain navigation path; request for anonymous cloud service certificate; vehicle requests cloud fragmentation service; navigation service and cloud service acquisition; route congestion notification and re-request service; real identity tracking eight steps. The anonymous navigation certificate and the anonymous cloud service certificate of the present invention make the real identity of the vehicle irrelevant to the certificate requesting the service; and the driving path information is obtained through the anonymous navigation certificate, and the download service is segmented according to the driving path, so that the vehicle can Download large files and be able to hide your identity and travel from attackers. The invention has high security, download efficiency and low overhead, and is suitable for VANET networks with high-speed movement of nodes, changeable topological structure and large scale.

Description

A method for data segment download service in vehicle network

technical field

The invention relates to the field of vehicle network communication security, in particular to an RSU-based security and privacy protection data segment download service method in the vehicle network.

Background technique

Currently, the market for in-vehicle entertainment and navigation systems is relatively mature. In-vehicle infotainment systems in the US market mainly include remote infotainment systems and electronic map-based navigation systems; in Japan, electronic map navigation systems have become standard configurations, for example, using maps with 3D effects and other information services; in Europe, More and more manufacturers of navigators and bluetooth wireless phones have joined the industrial chain, which has brought new vitality to the aftermarket.

Vehicle Network (VANET) not only performs well in driving safety, navigation and intelligent transportation, but also has better development prospects in other information services including entertainment, news, video conferencing, etc., and has become a research hotspot. VANET is characterized by its fast moving speed, intermittent connection, and rapid topology changes. However, compared with other wireless network branches, its power supply capacity, processing capacity, and storage capacity are not too limited. As a node, when enjoying information services such as entertainment, news, and file downloads, downloading and uploading are frequently used technologies. At present, the typical scheme algorithms are: VADD scheme Delay-bounded algorithm, D&S scheme , SADV scheme, SPAWN scheme, etc., but they only focus on the transmission of small files between vehicles, and are not suitable for large files. With the large-scale deployment of roadside infrastructure (RSU access points) in recent years, Trullols-Cruces et al. conducted research on the assisted download method in the highway scene, mainly using vehicles traveling in the same direction as assisted transmission, to Solve the problem of packet loss in the process of information transmission, and use vehicles traveling in opposite directions to transmit to increase the throughput of transmission. The assisted downloading method proposed by Fiore et al. mainly considers the urban downloading scenario, and studies the encounter opportunities of mobile nodes to improve its data transmission rate. The speed and driving route of the vehicle are the main considerations. The assisted download method is to analyze the traffic flow data information, deploy the appropriate AP site location, and then use the idle AP to predict the vehicle's driving route and the moment when the requesting vehicle meets, and Fiore et al. analyzed different assisted vehicle selection algorithms and data block Program. The above solution provides a downloading method, but does not involve how to protect the privacy of the vehicle during downloading.

In fact, the security of VANET has always been a research hotspot. Richard [11] summarizes the security issues and challenges of VANET in recent years. C. Zhang et al. proposed a RSU-assisted communication scheme, and vehicles can rely on RSU to verify messages sent by other vehicles. A.Wasef et al considered a group communication scheme and proposed a group key update protocol, but the cost of key update is quite expensive. In 2009, T.W Chim et al. proposed a new scheme SPECS (Communication Scheme for Enhanced Privacy Protection and Security), which defines a group communication protocol. Through a simple handshake protocol with the RSU, the vehicle can join any other vehicle in the group without the assistance of the RSU. However, this scheme cannot resist masquerading attacks very well. R.J.Hwang et al. proposed a self-updating pseudonym scheme based on identity encryption, but the vehicle revocation calculation cost of this scheme is relatively large. All the methods mentioned above emphasize how to protect privacy in the communication process. The invention can protect the privacy of the vehicle while downloading the data, and meets the safety requirement of the vehicle network.

The invention proposes a method for downloading data slices in a vehicle network. The invention can collect useful information through the RSU, provide navigation services for vehicles, and also provide download services for large files along the way. Based on this invention, it is possible to download large files while the vehicle is driving. Since the files are sent to each RSU segmented in advance according to the driving route and time, it can solve the problem of entering the next RSU because the download of a certain RSU is not completed. Downloading, which leads to waste of storage space caused by RSU repeatedly downloading backups, and using anonymous service certificates and pseudonyms when downloading, can hide the real identity of the vehicle and the vehicle's driving track, but it can be traced when there is a controversial message The true identity of the vehicle.

Contents of the invention

The purpose of the present invention is to provide a data segment download service method in the vehicle network, so as to realize the download of large files in a network-limited environment, and to protect the real identity and driving track of the vehicle from being leaked, so as to realize effective Conditional privacy protection.

In order to solve the above technical problems, the present invention uses an anonymous navigation service certificate to obtain the driving route, hides its true identity, divides the data according to the driving route, and the vehicle can download files along the way and obtain services according to the service number, but use pseudonyms when sending messages , thus hiding the driving trajectory. The specific technical scheme of the RSU-based security and privacy protection data segment download service method in the vehicle network proposed by the present invention is as follows: step 1, initializing the system: the authority TA selects public parameters for the roadside unit RSU, the navigation service provider NSP, Cloud service provider CSP and vehicle registration;

Step 2, requesting an anonymous navigation certificate: the vehicle requests an anonymous navigation certificate from the TA, and the TA authenticates the identity of the vehicle, and the TA issues an anonymous navigation certificate to the vehicle, and the certificate includes a navigation service number, which is used to obtain the navigation service later;

Step 3: Acquire the navigation route: NSP verifies the message signature and anonymous navigation certificate of the vehicle requesting the navigation service, and then the NSP generates a navigation route for the vehicle. The characteristic of the generated navigation route is that the route can calculate a time-prioritized route or a calculated distance according to the needs of the vehicle preferred path;

Step 4, requesting an anonymous cloud service certificate: the vehicle requests an anonymous cloud service certificate from TA, TA authenticates the identity of the vehicle, and TA issues an anonymous cloud service certificate to the vehicle, and the certificate contains a cloud service number, which is used to obtain cloud services later;

Step 5, the vehicle requests cloud fragmentation service: CSP verifies the message signature and anonymous navigation certificate of the vehicle requesting cloud service, and then the CSP fragments the service requested by the vehicle according to the driving path of the vehicle;

Step 6, acquisition of navigation service and cloud service: the vehicle obtains the required service according to the service number during driving, and the service feature is that the vehicle needs to negotiate a key with the RSU to prevent eavesdropping attacks;

Step 7, route congestion notification and re-request service: when the road condition changes, the RSU notifies the NSP of the road condition, and the NSP notifies the vehicle to change the route through the RSU, and the vehicle re-applies for the navigation service and cloud service;

Step 8, tracking of the real identity: when there is a message dispute, the authoritative organization will track the real identity of the vehicle according to the message and revoke the identity of the vehicle.

Described step one is further specifically:

Process 1, TA selects two cyclic groups G ₁ and G ₂ , a Tate pair mapping e:G ₁ ×G ₁ →G ₂ ; P is a generator of group G ₁ ; TA then selects three secure Hash functions H ₁ ,H ₃ :{0,1} ^* →G ₁ and And a secure encryption algorithm _Enck ();

Process 2, TA chooses a random parameter s as its own master key and a pair of traditional public-private key pair (SK _TA , PK _TA ), and TA calculates the public key P _pub =sP of the system, where PK _TA =SK _TA P; TA publishes system parameters (G ₁ , G ₂ , P, P _pub ,H ₁ ,H ₂ ,H ₃ ,PK _TA , _Enck ());

Process three, when the vehicle is registered, TA assigns a real identity RID _i ∈ G ₁ and the activation code PWD _i of the anti-tampering device to the vehicle V _i ; TA also assigns a pair of traditional public-private keys to the vehicle V _i in

Process 4, TA selects a random number for each RSU _i as the private key of RSU _i , and calculate As the public key of RSU _i , finally TA sends the private key and certificates from RSU _i Securely send to RSU _i , where R _i = (RSU _i ∥ L _i ), L _i is the location information of RSU _i ;

Step 5: TA distributes a pair of public and private keys (SK _NSP , PK _NSP ) and (SK _CSP , PK _CSP ) to NSP and CSP respectively, where PK _NSP =SK _NSP P and PK _CSP =SK _CSP P.

3. The data segment download service method in a kind of vehicle-mounted network according to claim 1, wherein said step 2 is further specifically:

Process 1, when vehicle V _i enters RSU _i , V _i selects a random number r′, and then V _i passes RSU _i Send it to TA; among them, NAV is the sign of the navigation service, and r′ is used to prevent the attacker from collecting information, so as to obtain the RSU of the vehicle passing by;

Process 2: TA decrypts message X and checks whether RID _i is in the revocation list. If not in the revocation list, TA issues an anonymous navigation certificate for the vehicle; TA calculates an anonymous navigation certificate for the vehicle V _i Among them, T represents a period of time, the certificate is only valid during this period of time, Num _NAV is the navigation service number, and the vehicle can obtain navigation from RSU only according to the navigation service number; then, TA sends it through RSU _i to vehicle V _i ;

According to the above steps, it can be known that the navigation certificate does not contain any information of the vehicle V _i , so the certificate is anonymous.

The third step is further specifically:

Process one, when starting the vehicle, the driver needs to input RID _i and PWD _i to activate the anti-tampering device, if the identity has not been revoked and the activation code is correct, then the activation of the anti-tampering device is successful, otherwise the anti-tampering device will stop further operate;

Process 2, the anti-tampering device generates a pseudonym and signature private key for the vehicle V _i ; the pseudonym ID ⁱ consists of two parts in r is a random number, the signature private key

Process three, the vehicle V _i generates a navigation route request message: first, the vehicle V _i generates a start and end point message M _NAV = (Start, Dest), where Start is the starting point and Dest is the destination; then V _i signs the message , calculate h _i =H ₂ (M _NAV ) and T=H ₃ (P _pub ), then generate the signature Next, V _i chooses a random number calculate and ψ _NSP = aPK _NSP . Finally, vehicle V _i sends a navigation route request message through RSU _i Enc _ψNSP (M _NAV ,ID ⁱ ,δ _i ,C _N )> to NSP;

Assume that RSU reports road conditions to NSP at regular intervals, including road congestion, vehicle speed and vehicle density;

Process 4, when NSP receives request message Y, NSP calculates Then NSP decrypts the message Y according to ψ' _NSP , and obtains M _NAV , ID ⁱ , δ _i and C _N respectively; first, NSP verifies the validity of C _N , and if it is valid, then verifies the correctness of the signature:

Proof of correctness: Compute h _i =H ₂ (M _NAV ), T = H ₃ (P _pub ) and

$\begin{array}{c}\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{{\mathrm{<span\; class="notranslate">\; ID</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}_{{\mathrm{<span\; class="notranslate">\; ID</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; ID</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span>\end{array}$

When there are many messages, we can also perform batch authentication: calculate T=H ₃ (P _pub ) and

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; ID</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Process 5, if the signature is valid, NSP generates a navigation path for vehicle V _i ; the origin and destination can be known according to M _NAV , and NSP can obtain various paths from the origin to the destination; The weight W _i of a section of road = α*l+(1-α)*t, where l is the length of the road, assuming that the setting unit is kilometers; t is the time required to pass through this section of road, based on the length of the road l and the road It is obtained from the driving speed of the vehicle on board, assuming that the setting unit is minutes; α is the proportion of the distance, if α is smaller, the proportion of time in the weight is greater;

Next, NSP sets several different values for α, and obtains the corresponding path according to the Dijkstra algorithm; when α is set to 0, the obtained path is the shortest time-consuming path; when α is 1, the obtained path is the shortest distance;

Finally, the NSP adds the random number N _NSP to these path signatures and returns them to the vehicle V _i through ψ′ _NSP encryption. The path information includes <(L _i ,t _i )(1≤i≤n),l _s , t _s >, L _i is the location that needs to pass through the RSU, t _i is the time required to pass through the RSU, n is the number of RSUs that need to pass through, l _s is the total travel distance, and t _s is the total travel time;

Process 6: After the vehicle V _i receives the navigation route message, V _i decrypts it with ψ _NSP , and _Vi obtains several corresponding navigation routes, and V _i selects one of them as its driving route, adds a random number N _NSP , and Encrypted by ψ _NSP and returned to NSP;

Process 7: NSP decrypts the message after receiving the message, and obtains the driving route selected by vehicle V _i ; NSP sends a navigation information to each RSU on the route through a secure network, and the navigation information includes <Route,RSU _next ,Num _NAV >, where Route is the road information of each RSU, and RSU _next is the information of the next RSU to arrive.

The fourth step is further specifically:

Similar to requesting an anonymous navigation certificate, the following protocol steps are performed:

Process 1, the vehicle V _i selects a random number r" through the RSU _i to Send it to TA; CSTO is the symbol of cloud service; r" is used to prevent attackers from collecting information, so as to obtain the RSU of vehicles passing by;

Process 2: TA selects a cloud service number Num _CSTO for the service, and calculates an anonymous cloud service certificate for vehicle V _i Then, TA sends through RSU _i Give the vehicle V _i .

The fifth step is further specifically:

When the vehicle is driving on the road, the vehicle needs to download big data temporarily. We perform the following steps to download the data:

Process 1, the anti-tampering device generates a pseudonym and signature private key for the vehicle V _i ; the pseudonym ID ⁱ consists of two parts in r is a random number, the signature private key

Process 2, the vehicle generates a cloud service request: first, the vehicle V _i generates a request data message _MCSP , then V _i signs the message, and calculates h _i =H ₂ (M _CSP ) and T=H ₃ (P _pub ), Then generate the signature Next, V _i chooses a random number calculate and ψ _CSP ＝ bPK _CSP ; finally, vehicle V _i sends a navigation path request message through RSU _i to CSP; Stop refers to the information that the vehicle may stop on the way;

Process three, when the NSP receives the request message Z, the CSP calculates Then the CSP decrypts the message Z according to ψ′ _NSP , and obtains M _CSP , ID ⁱ , δ _i , C _CSTO ; First, CSP verifies the validity of C _CSTO , and if it is valid, then verifies the correctness of the signature;

Process 4, if the signature is valid, the CSP provides fragmentation services for the vehicle V _i ; first, the CSP checks the current location of the vehicle V _i , which can be known from the RSU that forwards the message, and then, according to It can be known which RSUs the vehicle has passed and the time and stay time in the RSU. Therefore, the CSP fragments the data requested by V _i to ensure that each fragment can be sent to V _i in each RSU under normal circumstances; CSP Encrypt each shard, and then pass the encrypted data and cloud service number to each RSU through a secure network;

In process five, the CSP also sends the key k of the encrypted segment to the vehicle V _i .

Said step six is further specifically:

After obtaining the navigation path and cloud slice service, the vehicle obtains the navigation and download service at the RSU:

Process 1, RSU _i conducts a certificate every once in a while Broadcast, for example, once every 5s;

Process 2, V _i chooses a random number calculate and Vehicle V _i sends a navigation request message to RSU _i r _NAV is a random number; similarly, V _i can also send a download request message to RSU _i

Process three, RSU _i receives the request message, and calculates Decrypt to obtain the request content; then, RSU _i sends the forward route to the next RSU to V _i according to the navigation service number, and the content is in Encrypt; similarly, according to the cloud service number, send the downloaded data to V _i with the random number r _CSTO attached;

After other vehicles obtain the message, they cannot decrypt the message, so these messages have no effect on other vehicles. According to the attached random number, the vehicle can know whether the message is its own request message.

Said step seven is further specifically:

When there is a major change in the road surface, that is, the road surface is suddenly blocked or a traffic accident occurs, the vehicle needs to be notified to make changes to the driving route;

Process 1, the RSU that has a situation notifies the NSP, and the NSP notifies all other RSUs that include the RSU in the path, and then the NSP sends the route navigation service number to the RSU;

Process 2: RSU detects the vehicle using the navigation service number for navigation, and notifies the vehicle of the road conditions;

Process 3, the vehicle verifies whether the message comes from RSU, if it comes from RSU, the vehicle re-applies for navigation service and finds a new path;

Process 4. The vehicle notifies the cloud service provider through the RSU. The cloud service provider finds out the service RSU according to the cloud service number, and notifies the RSU after waiting for a certain period of time. The storage can be deleted, and the storage space can be recovered. The vehicle needs to restart according to the new navigation path. Apply for cloud services.

The eighth step is further specifically:

Process 1, according to the pseudonym of the vehicle and the system master key s, TA can calculate the real identity of the vehicle From then on, the vehicle cannot access any services; the proof of correctness is as follows:

Description of drawings

FIG. 1 is a flow chart of a data segment download service method based on RSU security and privacy protection in a vehicle network provided by an embodiment of the present invention.

Fig. 2 is a flow chart of requesting an anonymous navigation certificate provided by an embodiment of the present invention.

FIG. 3 is a flow chart of obtaining a navigation route provided by an embodiment of the present invention.

Fig. 4 is a flow chart of obtaining navigation and cloud services provided by an embodiment of the present invention.

FIG. 5 is a flowchart of path congestion notification and re-request services provided by an embodiment of the present invention.

detailed description

As shown in Figure 1, the communication method of the present invention has 8 steps in total, which are respectively:

1) Initialization system: TA selects public parameters and registers RSU, NSP, CSP and vehicles;

2) Request an anonymous navigation certificate: the vehicle requests an anonymous navigation certificate from TA, TA authenticates the identity of the vehicle, and TA issues an anonymous navigation certificate to the vehicle;

3) Get the navigation path: NSP verifies the message signature and anonymous navigation certificate of the vehicle requesting the navigation service, and then NSP generates the navigation path for the vehicle;

4) Request an anonymous cloud service certificate: the vehicle requests an anonymous cloud service certificate from TA, TA authenticates the identity of the vehicle, and TA issues an anonymous cloud service certificate to the vehicle;

5) The vehicle requests cloud fragmentation service: CSP verifies the message signature and anonymous navigation certificate of the vehicle requesting cloud service, and then the CSP fragments the service requested by the vehicle according to the driving path of the vehicle;

6) Acquisition of navigation service and cloud service: the vehicle obtains the required service according to the service number during driving;

7) Path congestion notification and re-request service: When the road conditions change, the RSU notifies the NSP of the road conditions, and the NSP notifies the vehicle to change the route through the RSU, and the vehicle re-applies for navigation services and cloud services;

8) Tracking of the real identity: when there is a message dispute, the authoritative organization will track the real identity of the vehicle according to the message and revoke the identity of the vehicle.

The present invention will be further described below in combination with specific embodiments and accompanying drawings.

1) Initialization system: TA selects public parameters and registers RSU, NSP, CSP and vehicles;

Step 1.1, TA selects two cyclic groups G ₁ and G ₂ , and a Tate pair mapping e: G ₁ ×G ₁ →G ₂ . P is a generator of the group _G1 . TA then selects three safe Hash functions H ₁ , H ₃ : {0,1} ^* → G ₁ and And a secure encryption algorithm _Enck ().

Step 1.2, TA chooses a random parameter s as its master key and a traditional public-private key pair (SK _TA , PK _TA ), and TA calculates the system's public key P _pub =sP, where PK _TA =SK _TA P. TA publishes system parameters (G ₁ , G ₂ , P, P _pub , H ₁ , H ₂ , H ₃ , PK _TA , _Enck ()).

Step 1.3, when the vehicle is registered, TA assigns a real identity RID _i ∈ G ₁ and an activation code PWD _{i of the anti-tampering device to the vehicle V i .} TA also assigns a pair of traditional public-private keys to vehicle V _i in

Step 1.4, TA chooses a random number for each RSU _i as the private key of RSU _i , and calculate As the public key of RSU _i , finally TA sends the private key and certificates from RSU _i Securely send to RSU _i , where R _i =(RSU _i ∥ L _i ), and L _i is the location information of RSU _i .

Step 1.5, TA distributes a pair of public and private keys (SK _NSP , PK _NSP ) and (SK _CSP , PK _CSP ) to NSP and CSP respectively, where PK _NSP =SK _NSP P, PK _CSP =SK _CSP P.

2) Request an anonymous navigation certificate: As shown in Figure 2, the vehicle requests an anonymous navigation certificate from TA, and TA authenticates

To verify the identity of the vehicle, TA issues an anonymous navigation certificate for the vehicle;

Step 2.1, when vehicle V _i enters RSU _i , V _i selects a random number r′, and then V _i passes RSU _i Send it to TA.

Step 2.2, TA decrypts message X, and checks whether RID _i is in the revocation list. If not in the revocation list, go to step 2.3, otherwise go to step 2.4.

Step 2.3, TA issues an anonymous navigation certificate for the vehicle, and TA calculates an anonymous navigation certificate for the vehicle V _i TA sent via RSU _i Give the vehicle V _i .

In step 2.4, the vehicle identity has been revoked, and the request for an anonymous navigation certificate fails.

According to the above steps, it can be seen that the navigation certificate does not contain any information of the vehicle _Vi , so the certificate is anonymous.

3) Obtaining the navigation path: as shown in Figure 3, the NSP verifies the message signature and the anonymous navigation certificate of the vehicle requesting the navigation service, and then the NSP generates a navigation path for the vehicle;

Step 3.1, when starting the vehicle, the driver inputs RID _i and PWD _i to activate the anti-tampering device, if the identity has not been revoked and the activation code is correct, then the activation of the anti-tampering device is successful, go to step 3.2, otherwise the anti-tampering device will Stop further manipulation, go to step 3.10.

Step 3.2, the anti-tampering device generates a pseudonym and a signature private key for the vehicle V _i . The pseudonym ID ⁱ consists of two parts in r is a random number. signature private key

Step 3.3, vehicle V _i generates a navigation route request message: First, vehicle V _i generates a start and end point message M _NAV =(Start, Dest), where Start is the starting point and Dest is the destination. Then V _i signs the message, calculates h _i =H ₂ (M _NAV ) and T=H ₃ (P _pub ), then generates the signature

Step 3.4, V _i chooses a random number calculate and ψ _NSP = aPK _NSP . Vehicle Vi sends a navigation route request message through RSU _i to NSP.

Step 3.5, when NSP receives request message Y, NSP calculates Then NSP decrypts the message Y according to ψ' _NSP , and obtains M _NAV , ID ⁱ , δ _i and C _N respectively. First, NSP verifies the validity of _CN , if valid, go to step 3.6, otherwise go to step 3.11.

Step 3.6, verify the correctness of the signature: calculate h _i =H ₂ (M _NAV ), T=H ₃ (P _pub ) and When there are many messages, we can also perform batch authentication: calculate T=H ₃ (P _pub ) and

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; ID</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

If formula (1) is established, go to step 3.7, otherwise go to step 3.11.

Step 3.7, the signature is valid, and the NSP generates a navigation path for the vehicle V _i . According to the M _NAV , the origin and destination can be known, and the NSP can obtain various paths from the origin to the destination. We assign a value to each section of road, and the weight of each section of road W _i = α*l+(1-α)*t, where l is the length of the road, assuming that the setting unit is kilometers, and t is required to pass through this section of road Time (according to the road length l and the speed of vehicles on the road), assuming that the setting unit is minutes. α is the proportion of distance. If α is smaller, it means that the proportion of time in the weight is greater. Next, NSP sets several different values for α, and obtains the corresponding path according to the Dijkstra algorithm. When α is set to 0, the resulting path is the shortest time-consuming path, and when α is 1, the resulting path is the shortest distance. Finally, NSP adds these path signatures to the random number N _NSP and returns it to the vehicle V _i through ψ′ _NSP encryption.

Step 3.8: After the vehicle V _i receives the navigation route message, V _i decrypts it with ψ _NSP , and V _i obtains several corresponding navigation routes. V _i selects one of them as its driving route, adds a random number N _NSP , and Encrypted by ψ _{NSP and} returned to NSP.

Step 3.9, NSP decrypts the message after receiving it, and obtains the driving route selected by the vehicle V _i . NSP sends a navigation message to each RSU passing by through a secure network. The navigation message includes <Route, RSU _next , Num _NAV >, where Route is the road information passing through each RSU, and RSU _next is the next RSU arriving.

Step 3.10, if the vehicle is revoked or the input of RID _i and PWD _i is wrong, input it again.

In step 3.11, the authentication fails and the protocol is terminated.

So far, the vehicle has obtained the navigation route, and the vehicle can obtain services according to the navigation service number.

4) Request an anonymous cloud service certificate: the vehicle requests an anonymous cloud service certificate from TA, TA authenticates the identity of the vehicle, and TA issues an anonymous cloud service certificate to the vehicle;

Step 4.1, vehicle V _i selects a random number r" through RSU _i to Send it to TA.

Step 4.2, TA decrypts message X', and checks whether RID _i is in the revocation list. If not in the revocation list, go to step 4.3, otherwise go to step 4.4.

Step 4.3, TA selects a cloud service number Num _CSTO for this service, and calculates an anonymous cloud service certificate for vehicle V _i Then, TA sends through RSU _i Give the vehicle V _i .

In step 4.4, the vehicle identity has been revoked, and the request for the anonymous cloud service certificate fails.

According to the above steps, it can be seen that the cloud service certificate does not contain any information of the vehicle _Vi , so the certificate is anonymous.

5) The vehicle requests cloud fragmentation service: as shown in Figure 4, the CSP verifies the message signature and anonymous navigation certificate of the vehicle requesting cloud service, and then the CSP fragments the service requested by the vehicle according to the driving path of the vehicle;

Step 5.1, the anti-tampering device generates a pseudonym and a signature private key for the vehicle V _i . The pseudonym ID ⁱ consists of two parts in r is a random number. signature private key

Step 5.2, the vehicle generates a cloud service request: first, the vehicle V _i generates a request data message M _CSP , then V _i signs the message, and calculates h _i =H ₂ (M _CSP ) and T=H ₃ (P _pub ), Then generate the signature

Step 5.3, V _i chooses a random number calculate and ψ _CSP = bPK _CSP . Finally, vehicle V _i sends a navigation route request message through RSU _i to the CSP. in Stop refers to the information that the vehicle may stop on the way.

Step 5.4, when the NSP receives the request message Z, the CSP calculates Then the CSP decrypts the message Z according to ψ′ _NSP , and obtains M _CSP , ID ⁱ , δ _i , C _CSTO . First, CSP verifies the validity of C _CSTO , if valid, go to step 5.5, otherwise go to step 5.8.

Step 5.5, verify the correctness of the signature. Calculate _hi = H ₂ (M _CSP ), T = H ₃ (P _pub ) and When there are many messages, we can also perform batch authentication: calculate T=H ₃ (P _pub ) and

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; ID</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

If formula (2) is established, go to step 5.6, otherwise go to step 5.8.

In step 5.6, the signature is valid, and the CSP performs fragmentation service for the vehicle V _i . First, the CSP checks the current location of the vehicle _Vi , which can be known from the RSU that forwards the message, and then, according to It is known which RSUs the vehicle has passed and the travel time and residence time in the RSUs. Therefore, the CSP divides the data requested by V _i into fragments to ensure that each fragment can be sent to V _i in each RSU under normal circumstances. CSP encrypts each shard, and then transmits the encrypted data and cloud service number to each RSU through a secure network.

In step 5.7, the CSP also sends the key k of the encrypted segment to the vehicle V _i at the same time.

In step 5.8, the authentication fails and the protocol is terminated.

So far, the vehicle has obtained the cloud fragmentation service, and the vehicle can obtain the service according to the cloud service number.

6) Acquisition of navigation service and cloud service: the vehicle obtains the required service according to the service number during driving;

Step 6.1, RSU _i certificates every once in a while Broadcast, for example once every 5s.

Step 6.2, V _i chooses a random number calculate and Vehicle V _i sends a navigation request message to RSU _i r _NAV is a random number and download request message

Step 6.3, RSU _i receives the request message and calculates Decrypt to obtain the request content. Then, RSU _i sends the forward route to the next RSU to V _i according to the navigation service number, and the content is in Encrypt; similarly, according to the cloud service number, send the downloaded data to V _i with the random number r _CSTO attached.

After other vehicles obtain the message, they cannot decrypt the message, so these messages have no effect on other vehicles. According to the attached random number, the vehicle can know whether the message is its own request message.

7) Route congestion notification and re-request service: As shown in Figure 5, when the road conditions change, the RSU notifies the NSP of the road conditions, and the NSP notifies the vehicle to change the route through the RSU, and the vehicle re-applies for navigation services and cloud services;

Step 7.1, the RSU that has a situation notifies the NSP, and the NSP notifies all other RSUs that include the RSU in the route, and then the NSP sends the route navigation service number to the RSU.

Step 7.2, RSU detects the vehicle using the navigation service number for navigation, and notifies the vehicle of the road conditions.

Step 7.3, the vehicle verifies whether the message is from RSU, if it is from RSU, go to step 7.4, otherwise go to step 7.6.

In step 7.4, the vehicle re-applies for the navigation service to find a new path.

In step 7.5, the vehicle notifies the cloud service provider through the RSU, and the cloud service provider finds out the service RSU according to the cloud service number, and notifies the RSU after waiting for a certain period of time to delete the storage and reclaim the storage space. The vehicle needs to re-apply for cloud services based on the new navigation path.

In step 7.6, the vehicle continues to drive along the original path.

8) Tracking of the real identity: when there is a message dispute, the authoritative organization will track the real identity of the vehicle according to the message and revoke the identity of the vehicle.

Step 8.1, according to the pseudonym of the vehicle and the system master key s, TA can calculate the real identity of the vehicle From then on, the vehicle cannot access any services.

Claims (9)

1. data fragmentation download service method in a vehicle-mounted net, it is characterised in that comprise the steps of

Step one, initializes system: authoritative institution TA chooses common parameter, for roadside unit RSU, navigation service provider NSP, Cloud service provider CSP and vehicle are registered；

Step 2, request anonymity navigation certificate: vehicle is to TA request anonymity navigation certificate, and the identity of TA certification vehicle, TA is car Provide anonymity navigation certificate, described certificate comprises navigation Service number, for the later stage obtain navigation Service；

Step 3, obtains the information signature of guidance path: NSP checking request navigation Service vehicle and anonymous navigation certificate, then NSP is that vehicle generates guidance path, and described generation guidance path is characterised by that path can calculate the time excellent according to vehicle demand First path or calculate the path that distance is preferential；

Step 4, the anonymous cloud service certificate of request: vehicle is to the anonymous cloud service certificate of TA request, the identity of TA certification vehicle, TA Providing anonymous cloud service certificate for vehicle, described certificate comprises cloud service number, obtains cloud service for the later stage；

Step 5, the information signature of vehicle request cloud sliced service: CSP checking request cloud service vehicle and anonymous navigation certificate, Then CSP carries out burst according to the driving path of vehicle, the service that vehicle is asked by CSP；

Step 6, navigation Service and cloud service obtain: vehicle is in the process of moving according to service number, the service needed for acquisition, institute State service features and be that vehicle needs and RSU carries out key agreement, prevent eavesdropping from attacking；

Step 7, path congestion notice and re-request service: when pavement behavior changes, RSU notice NSP road surface occurs Situation, NSP changes path by RSU notice vehicle, and vehicle applies for navigation Service and cloud service again；

Step 8, the tracking of true identity: occur when message is disputed on, authoritative institution tracks the true body of vehicle according to message Part, and described testing vehicle register is cancelled.

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step One further particularly as follows:

Process one, TA selects two cyclic groups G₁And G₂, a Tate is to mapping e:G₁×G₁→G₂；P is crowd G₁A generation Unit；The Hash function H of 3 safety of TA reselection₁,H₃:{0,1}^*→G₁WithEncryption with a safety is calculated Method Enc_k( )；

Process two, TA selects a random parameter s as the master key of oneselfPublic private key pair (the SK traditional with a pair_TA, PK_TA), and TA calculates the PKI P of system_pub=sP, wherein PK_TA=SK_TAP；TA public address system parameter (G₁,G₂,P,P_pub, H₁,H₂,H₃,PK_TA,Enc_k( ))；

Process three, when vehicle registration, TA is to vehicle V_iDistribute real identity RID_i∈G₁Activation with tamper resistant device Code PWD_i；TA also gives vehicle V_iDistribute a pair traditional public and private keyWherein

Process four, TA is each RSU_iSelect a random numberAs RSU_iPrivate key, and calculateAs RSU_iPKI, last TA is by private keyAnd RSU_iCertificate Safe is sent to RSU_i, wherein R_i=(RSU_i‖L_i), L_iIt is RSU_iPositional information；

Process five, TA is that NSP and CSP distributes a pair public and private key (SK respectively_NSP,PK_NSP)、(SK_CSP,PK_CSP), wherein PK_NSP= SK_NSPP, PK_CSP=SK_CSPP。

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Two further particularly as follows:

Process one, vehicle V_iEnter RSU_iTime, V_iSelect random number r ', then a V_iPass through RSU_iBy X=It is sent to TA；Wherein, NAV is the mark of navigation Service, and r ' is used to prevent assailant from collecting Information, thus obtain the RSU of vehicle process；

Process two, TA deciphers message X, checks RID_iWhether in revocation list.If not in revocation list, TA is that vehicle is sent out Put anonymous navigation certificate；TA is vehicle V_iCalculate anonymity navigation certificate Wherein, T represents a time period, and certificate is only just effective in this time period, Num_NAVBeing navigation Service number, vehicle only has root Navigation could be obtained at RSU according to navigation Service number；Then, TA passes through RSU_iSendTo vehicle V_i；

According to above-mentioned steps, can know in this navigation certificate and not comprise vehicle V_iAny information, so certificate is anonymous.

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Three further particularly as follows:

Process one, when starting the vehicle, driver needs to input RID_iAnd PWD_iActivate tamper resistant device, if identity not by Cancelling, and active coding is correct, then tamper resistant device activates successfully, otherwise tamper resistant device will stop further behaviour Make；

Process two, tamper resistant device is vehicle V_iGenerate assumed name and signature private key；Assumed name IDⁱComprise two partsIts InR is a random number, signature private key

Process three, vehicle V_iGenerate guidance path request message: first, vehicle V_iGenerate beginning and end message M_NAV= (Start, Dest), wherein Start is departure place, and Dest is destination；Then V_iThis message is signed, calculates h_i=H₂ (M_NAV) and T=H₃(P_pub), then generate signatureThen, V_iSelect a random numberCalculateAnd ψ_NSP=aPK_NSP.Finally, vehicle V_iPass through RSU_iSend guidance path request messageTo NSP；

Assume that RSU reports pavement behavior to NSP at set intervals, including Congestion Level SPCC, Vehicle Speed and the car on road surface Density；

Process four, when NSP receives request message Y, NSP calculatesThen NSP is according to ψ ＇_NSPDeciphering Message Y, respectively obtains M_NAV,IDⁱ,δ_iAnd C_N；First, NSP verifies C_NEffectiveness, if effectively, then verify the correct of signature Property:

Justifying property: calculate h_i=H₂(M_NAV), T=H₃(P_pub) and

$\begin{array}{c}e(P,{\mathrm{\&delta;}}_i)=e(P,rT+h_i{d}_{{\mathrm{ID}}^i})\\ =e\left(P,rT\right)e\left(P,h_i{d}_{{\mathrm{ID}}^i}\right)\\ =e\left({\mathrm{ID}}_1^i,T\right)e\left(h_i{Q}_i,P_{pub}\right)\end{array}$

When message is more, we can also perform batch certification: calculates T=H₃(P_pub) and

$e(P,\mathrm{\&delta;})=e({\mathrm{ID}}_1,T)e({\mathrm{\&Sigma;}}_{i=1}^n{h}_i{Q}_i,P_{pub});$

Process five, if signature is effective, NSP is vehicle V_iGenerate guidance path；According to M_NAVUnderstand departure place and destination, NSP can obtain various paths from origin to destination；Each section of highway is carried out assignment, the weights W of every stretch_i=α * L+ (1-α) * t, wherein l is the length of highway, it is assumed that setting unit is km；T is the time needed through this section of highway, is root Draw according to Vehicle Speed in road length l and highway, it is assumed that setting unit is minute；α is distance proportion, if α In the least explanation weights, time proportion is the biggest；

It follows that NSP arranges several different value to α, according to dijkstra's algorithm, obtain corresponding path；When α is set to 0 Time, gained path is the shortest, and when α is 1, gained path is exactly that distance is the shortest；

Finally, these several paths signature is added random number N by NSP_NSPAnd by ψ ＇_NSPVehicle V is returned in encryption_i, in routing information Including ＜ (L_i,t_i)(1≤i≤n),l_s,t_s＞, L_iIt is to need the position through RSU, t_iIt is the time needed through this RSU, n It is to need the quantity through RSU, l_sIt is total traveling distance, t_sIt it is total running time；

Process six, vehicle V_iAfter receiving guidance path message, V_iUse ψ_NSPIt is decrypted, V_iObtain corresponding a few bar navigation road Footpath, V_iSelect wherein one as after the driving path of oneself plus random number N_NSP, and pass through ψ_NSPEncryption returns to NSP；

Process seven, NSP deciphers after receiving message, it is thus achieved that vehicle V_iAfter the driving path selected；NSP is sent out by the network of safety Giving mono-navigation information of each RSU of approach, navigation information includes ＜ Route, RSU_next,Num_NAV＞, wherein Route is Through each RSU road information, RSU_nextIt is the next RSU information arrived.

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Four further particularly as follows:

Similar to request anonymity navigation certificate, perform following protocol steps:

Process one, vehicle V_iA random number r is selected " to pass through RSU_iWillIt is sent to TA； CSTO is the mark of cloud service；R " is used to prevent assailant's gather information, thus obtains the RSU of vehicle process；

Process two, TA is that a cloud service Num is chosen in this service_CSTO, and be vehicle V_iCalculate anonymous cloud service certificateThen, TA passes through RSU_iSendTo vehicle V_i。

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Five further particularly as follows:

When vehicle travels on road, vehicle temporary needs downloads big data, and we perform following steps, carry out under data Carry:

Process one, tamper resistant device is vehicle V_iGenerate assumed name and signature private key；Assumed name IDⁱComprise two partsIts InR is a random number, signature private key

Process two, vehicle generates cloud service request: first, vehicle V_iGenerate request data message M_CSP, then V_iThis message is entered Row signature, calculates h_i=H₂(M_CSP) and T=H₃(P_pub), then generate signature Then, V_iSelect one with Machine numberCalculateAnd ψ_CSP=bPK_CSP；Finally, vehicle V_iPass through RSU_iSend guidance path request message To CSP； Stop refers to the information that vehicle on the way may stop；

Process three, when NSP receives request message Z, CSP calculatesThen CSP is according to ψ ＇_NSPDeciphering Message Z, respectively obtains M_CSP,IDⁱ,δ_i,C_CSTO；First, CSP verifies C_CSTOEffectiveness, if effectively, then verify signature Correctness；

Process four, if signature is effective, CSP is vehicle V_iCarry out sliced service；First, CSP checks vehicle V_iPresent bit Put, from the RSU of forwarding message, then, according toUnderstand vehicle through which RSU and in RSU travel time and The time of staying, therefore, CSP is by V_iThe data of request carry out burst, it is ensured that the most each burst is energy in each RSU Enough it is sent to V_i；Each burst is encrypted by CSP, then encryption data and cloud service number is given by the network delivery of safety Each RSU；

Process five, the key k of encryption burst is the most also sent to vehicle V by CSP_i。

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Six further particularly as follows:

After obtaining guidance path and cloud sliced service, vehicle obtains at RSU and navigates and download service:

Process one, RSU_iCarry out a certificate at set intervalsBroadcast, such as 5s is once；

Process two, V_iSelect a random numberCalculateWithVehicle V_iTo RSU_iSend navigation Request messager_NAVIt it is a random number；Same V_iCan also be to RSU_iSend and download Request message

Process three, RSU_iReceive request message, calculateIt is decrypted, obtains request content；Then, RSU_i According to navigation Service number, the advance route arriving next RSU is sent to V_i, content is usedIt is encrypted；Equally, according to Download data are sent to V by cloud service number_iAnd incidentally go up random number r_CSTO；

Other vehicles can not decipher this message, so these message are not have any effect for other vehicles after obtaining message , according to subsidiary random number, vehicle can know that whether this message be the request message of oneself.

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Seven further particularly as follows:

When road surface occurs great change, i.e. road surface blocks suddenly or vehicle accident occurs, and needs to notify vehicle, to travelling road Change is made in footpath；

Process one, contains other all RSU of this RSU in RSU notice NSP, the NSP notification path of situation occurred, then NSP sends out Send path navigation service number to RSU；

Process two, RSU detects and uses this navigation Service number to carry out the vehicle navigated, and notifies the shape that this vehicle road occurs Condition；

Process three, vehicle verifies whether this message comes from RSU, and if from RSU, navigation Service applied for again by vehicle, finds New path；

Process four, vehicle notifies cloud service provider by RSU, and cloud service provider finds out service according to cloud service number RSU, notifies RSU after waiting certain time, can delete this storage, reclaiming memory space, vehicle needs according to new navigation road Cloud service is applied in footpath again.

Data fragmentation download service method in the vehicle-mounted net of one the most according to claim 1, it is characterised in that described step Eight further particularly as follows:

Process one, according to the assumed name of vehicleWith the true body that system master key s, TA can calculate vehicle PartFrom this, vehicle can not obtain any service；Correctness proof is as follows: