CN111107071B - Electric vehicle charging service method capable of protecting privacy - Google Patents

Abstract

The invention discloses an electric vehicle charging service method capable of protecting privacy, by which an electric vehicle generates a temporary token by using a key pair distributed by a charging service provider and a pseudo identity distributed by a credible center, authenticates a roadside unit by using the temporary token, sends a seed key required by charging panel authentication to the electric vehicle by passing a rear roadside unit, performs challenge response by using a one-time session key generated by the seed key to complete authentication, and provides the charging service for the electric vehicle by passing a rear charging panel after authentication. By the method disclosed by the invention, better management on the behavior of the electric automobile can be realized.

Description

Electric vehicle charging service method capable of protecting privacy

Technical Field

The invention relates to the technical field of electric automobiles, in particular to an electric automobile charging service method capable of protecting privacy.

Background

With the increasingly prominent global environmental and energy problems, the development of new energy vehicles such as electric vehicles is greatly supported and encouraged by countries in the world. The wireless charging technology is paid more and more attention with the advantages of safe operation, convenient use, low maintenance cost, good user experience and the like, and is one of the main development trends of the future electric automobile power supply technology. However, in the existing authentication method for wireless charging of the electric vehicle, because the electric vehicle directly uses the real identity for charging authentication, a malicious entity can easily obtain the real identity of the vehicle in the charging authentication and service process, and expose the driving track of the vehicle, thereby invading the privacy of the vehicle owner.

Disclosure of Invention

In order to solve the technical problems, the invention provides an electric vehicle charging service method capable of protecting privacy, which adopts the technical scheme that:

an electric vehicle charging service method capable of protecting privacy comprises the following steps:

s1: an EV (Electric Vehicle) verifies the correctness of a certificate broadcasted by an RSU (Road Side Unit) after receiving the certificate, and extracts a public key PK of the RSU from the certificate after the certificate passes the verification_RSUAnd according to the public key PK_RSUCalculating a temporary session key K of the EV and the RSU_EV,RSU(ii) a The local database of the EV is prestored with a set PID (proportion integration differentiation) formed by n pseudo identities which are distributed by a trusted center TA and correspond to the real identity of the EV, and a set (PPK, PSK) formed by a key pair which is distributed by a charging service provider CSP for each pseudo identity in the pseudo identity set PID and used for authenticating the charging service, wherein each key pair comprises a component PPK_jAnd component PSK_j，PPK_jRepresenting key components independent of pseudo-identity, PSK_jRepresenting a key component associated with a pseudo-identity, PID ═ PID₁,PID₂,…PID_n}，(PPK,PSK)＝{(PPK₁,PSK₁),(PPK₂,PSK₂),…(PPK_n,PSK_n)}，j＝{1,2…n}；

S2: EV selects a pseudo-identity PID from the pseudo-identity set and the key pair set respectively_iAnd a corresponding key pair (PPK)_i,PSK_i) To calculate a temporary token TOK for RSU authentication identity_i，i＝{1,2…n}

S3: the EV sends a charging request to the RSU, wherein the charging request comprises a temporary token TOK_iAnd by a temporary session key K_EV,RSUEncrypted pseudo-identity information and key pair information;

s4: the RSU calculates a temporary session key K between the RSU and the EV after receiving the charging request_EV,RSUThe charging request is decrypted by the pseudo identity information and the key pair information;

s5: RSU based on received TOK_iJudging whether the EV is a legal authorized user or not by the decrypted pseudo-identity information and the decrypted key pair information, if so, turning to S7, and otherwise, turning to S6;

s6: the RSU refuses the charging service;

s7: the RSU calculates a seed key alpha of a temporary session key between the EV and a CP (Charging pad), binds the calculated seed key alpha with the pseudo identity information of the EV and passes through K_RSU,CPSending the encrypted seed key to the CP, binding the calculated seed key with the pseudo identity information of the EV and passing through the K_EV,RSUEncrypted and sent to the corresponding EV, wherein K_RSU,CPRepresenting a temporary session symmetric key negotiated in advance between the RSU and the CP;

s8: EV passage K_EV,RSUDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iAnd use a one-time session key alpha_iGenerating an authentication code and transmitting the authentication code to the CP;

s9: CP through K_RSU,CPDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iVerifying the authentication code sent by the EV based on the one-time session key, andafter the verification is passed, providing charging service to the EV;

s10: CP totaling as PID_iThe marked EV provides the total electric energy, and sends corresponding total electric energy information to the RSU;

s11: the RSU generates PID according to the received total electric energy information_iBilling the identified EV and sending the bill to the corresponding EV;

s12: the RSU, upon receiving the EV's payment message, checks the bill and returns an acknowledgement message.

Further, before step S1, the method further includes the step of initializing the system, where the initializing the system includes the following sub-steps:

s011: the TA (Trusted Authority) generates the public parameters of the system and the public key PK of the TA according to the preset security parameters_TAAnd a private key SK_TA；

S012: CSP (Charging Service Provider) sends its own ID to TA_CSPRequesting registration;

s013: TA generates CSP public key PK after confirming CSP sent identity information is legal_CSPAnd a private key SK_CSPAnd generates the CSP public key certificate Cert by using the TA private key_CSPAnd the system public parameter, PK, is connected through a secure channel_CSP、SK_CSPAnd Cert_CSPIs sent to the CSP and then sent to the CSP,

representation through SK_TAFor ID_CSPAnd PK_CSPA signature generated after encryption;

s014: CSP generates corresponding ID for each CP in its management range_CPThen using the private key SK of CSP_CSPFor ID_CPGenerating a signature Sign_SKCSP(ID_CP) And sending the signature to a corresponding CP through a secure channel;

s015: RSU sends self identity information ID to TA_RSURequesting registration;

s016: the TA generates a public key PK of the RSU after confirming that the identity information sent by the RSU is legal_RSUPrivate key SK_RSUAnd public key certificate Cert of RSU_RSUAnd the system public parameter, PK, is connected through a secure channel_RSU、SK_RSUAnd Cert_RSUIs sent to the RSU and then sent to the RSU,

representation through SK_TAFor ID_RSUAnd PK_RSUA signature generated after encryption;

s017: the RSU negotiates a temporary session symmetric key for ensuring safe communication with the CP in the communication range of the RSU, and stores the negotiated temporary session symmetric key locally for subsequent safe communication;

s018: EV needing charging service sends its own real identity information RID to TA_EVRequesting registration;

s019: the TA generates a public key PK of the EV after confirming that the real identity information of the EV is legal_EVPrivate key SK_EVAnd the public key certificate Cert of the EV_EVAnd generates a set PID consisting of n pseudo-identities for the EV according to the real identity of the EV,

representation through SK_TAFor RID_EVAnd PK_EVA signature generated after encryption;

s020: TA uses its private key SK_TATrue identity RID for EV_EVSigning with corresponding pseudo identity PID to obtain

S021: TA sends the system public parameter, PK through the secure channel_EV、SK_EV、Cert_EVPID and

sending the information to the EV;

s022: and the EV stores a pseudo identity set PID corresponding to the real identity of the EV in a local tamper-proof equipment unit.

Further, the system public parameters comprise a generator P of the system cycle group and a one-way hash function of the system;

PID_j＝(PID_j，1，PID_j,2),PID_j，1and PID_j,2PID representing a pseudo-identity_jIs calculated by the formula PID in step S019_j,1＝d_jP compute meta-component PID_j，1By the formula

Compute meta-component PID_j,2，d_jRandom number indicating TA selection, H₁A first one-way hash function representing a system;

further, after the system initialization step and before step S1, the method further includes:

s031: EV sends a request M for subscribing charging service to CSP₁Wherein

t1 denotes EV Generation subscription charging service request M₁The time stamp generated at the time of the clock,

s032: the charging service provider CSP receives a request M for subscribing the charging service sent by the EV when registering₁Then, use private key SK_CSPDecrypt the message, if not, abort the session, otherwise check the timestamp t1 and use the public key PK of the TA_TAChecking signatures

If not, stopping the session, otherwise, recording the charging service registration information of the EV in a database and executing the step S033;

s033: the CSP generates n pairs of key pairs for authenticating the charging service for the EV, and generates a message M of the key pairs for authenticating the charging service using the set of key pairs₂And M is₂Is sent to the EV, wherein

t2 denotes a message M that the CSP generates a key pair for authenticating the charging service₂A time stamp generated;

s034: EV uses its private key SK_EVTo the received message M₂Decrypting, if not, terminating the session, otherwise, checking the timestamp t2 and using the CSP's public key PK_CSPChecking signatures

If not, aborting the session, otherwise storing a set of key pairs (PPK, PSK) for the authentication service on the tamper resistant device unit of the vehicle.

Further, step S033 includes:

CSP by formula PPK_j＝r_jP calculates the key components independent of the pseudo-identity and passes the formula PSK_j＝r_j+H₂(PID_j,PPK_j)·SK_CSPmod q computes a key component, r, associated with the pseudo-identity_jRandom number representing CSP selection, H₂A second one-way hash function representing the system.

Further, the step of the RSU negotiating the temporary session symmetric key with the CP includes:

s041: the CP verifies the correctness of the certificate broadcasted by the RSU after receiving the certificate, and extracts the public key PK of the RSU from the certificate after the verification is passed_RSUAnd selecting a random number mu to calculate K_CPAnd K_RSU,CP，K_CP＝μ·P，K_RSU,CP＝μ·PK_RSU；

S042: CP sending message

Giving RSU, wherein nonces represent random numbers selected by CP;

s043: RSU passes through CSP public key PK after receiving message sent by CP_CSPVerifying if the signature in the received message was signed by the CSP, e.g., by obtaining K_CPAnd formula K_RSU,CP＝SK_RSU·K_CPCalculate K_RSU,CPAnd using the calculated K_RSU,CPDecrypting the message to obtain a nonce and sending the message

Feeding the CP;

s044: CP uses K_RSU,CPAnd decrypting the received message, and judging whether the decrypted message is equal to nonce +1, if so, successfully negotiating the temporary session symmetric key between the RSU and the CP, otherwise, failing to negotiate the temporary session symmetric key between the RSU and the CP.

Further, the RSU and CP periodically update the temporary session symmetric key between the two.

Further, step S1 includes: EV according to formula K_EV,RSU＝x·PK_RSUCalculating a temporary session key K for secure communication with an RSU_EV,RSUX represents a random number for EV selection;

temporary token TOK_iComprises TOK_i,1And TOK_i,2Step S2 includes: EV passing formula TOK_i,1Calculating TOK as x.P_i,1And by the formula TOK_i,2＝PSK_i+H₃(PID_i,PPK_i,TOK_i,1Request, t 3). x mod q to calculate TOK_i,2，H₃A third one-way hash function representing the system, request representing charging parameter information, and t3 representing EV calculation TOK_iA time stamp generated;

step S3 includes: EV sends charging request M to RSU₃，

Step S4 includes: RSU by formula K_EV,RSU＝SK_RSU·TOK_i,1Calculate a temporary session key K between it and the EV_EV,RSUAnd decrypts the received M using the temporary session key₃Get { PID_i,PPK_i,t3}；

Step S5 includes: the RSU checks the timestamp t3 based on the received TOK_i,1、TOK_i,2And decrypted to obtain { PID_i,PPK_iJudging whether the equation for verifying the identity validity is established, if so, going to S7, otherwise, going toS6, wherein the equation for verifying the validity of the identity is:

TOK_i,2·P＝PPK_i+H₂(PID_i,PPK_i)·PK_CSP+H₃(PID_i,PPK_i,TOK_i,1,request,t3)·TOK_i,1。

further, step S7 includes:

s71: the RSU selects a random number alpha as a seed key for calculating a temporary session key between the EV and the CP, and calculates

RES₂＝HMACK_EV,RSU(PID_iα, t4), t4 represents the time stamp of RSU generation when calculating RES1 and RES2, RES₁Indicates the use of K_EV,RSUTo PID_iAlpha and t4 are encrypted to obtain a message, RES₂Representation to PID_iA, and t 4;

s72: RSU sends message M₄To EV and send message M₅For each CP controlled by the RSU, where M₄＝{RES₁,RES₂,t4}，

t5 denotes the RSU generation message M₅Time stamps generated.

Further, the method further comprises:

if the RSU does not receive the payment message of the EV within the preset time period, the pseudo identity information of the EV which does not pay the charging service fee successfully is recorded and sent to the TA, and the TA calculates the real identity corresponding to the pseudo identity information after receiving the pseudo identity information of the EV sent by the RSU and publishes the real identity of the EV.

According to the electric vehicle charging service method capable of protecting privacy, the electric vehicle generates the temporary token by using the key pair distributed by the charging service provider and the pseudo identity distributed by the credible center, the temporary token is used for authenticating the roadside unit, after the authentication is passed, the roadside unit sends the seed key required by the authentication of the electric vehicle and the charging panel, the challenge response is carried out by using the one-time session key generated by the seed key to finish the authentication, and after the authentication is passed, the charging panel provides service for the electric vehicle to start charging.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic structural diagram of a charging service system provided in the present invention;

FIG. 2 is a schematic flow chart of a privacy-protecting electric vehicle charging service method provided by the present invention;

FIG. 3 is a schematic diagram of a system initialization process;

FIG. 4 is a schematic diagram of an electric vehicle registration process;

FIG. 5 is a schematic flow chart illustrating the process of accessing the charging service by the electric vehicle;

FIG. 6 is a schematic diagram of a bill generation and payment process;

fig. 7 is a schematic diagram of an identity tracing process.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

The present embodiment provides an electric vehicle charging service method capable of protecting privacy, which is applied to an electric vehicle charging service system, and the system structure is shown in fig. 1, and includes TA, CSP, RSU, CP and EV. The TA is responsible for system initialization and distribution of public and private key pairs of each entity in the system, the CSP is responsible for registration and authorization of the EV, the RSUs are independent of each other, the RSU is responsible for authenticating the EV and distributing a one-time session key used for authenticating a CP controlled by the EV, and the CP is responsible for providing charging service for the authenticated and authorized EV.

Specifically, the flow of the electric vehicle charging service method capable of protecting privacy provided by this embodiment may be shown in fig. 2, and includes the following steps:

s1: the electric vehicle EV verifies the correctness of the certificate after receiving the certificate broadcasted by the roadside unit RSU, and extracts the public key PK of the RSU from the certificate after the verification is passed_RSUAnd according to the public key PK_RSUCalculating a temporary session key K of the EV and the RSU_EV,RSU(ii) a The local database of the EV is prestored with a set PID (proportion integration differentiation) formed by n pseudo identities which are distributed by a trusted center TA and correspond to the real identity of the EV, and a set (PPK, PSK) formed by a key pair which is distributed by a charging service provider CSP for each pseudo identity in the pseudo identity set PID and used for authenticating the charging service, wherein each key pair comprises a component PPK_jAnd component PSK_j，PPK_jRepresenting key components independent of pseudo-identity, PSK_jRepresenting a key component associated with a pseudo-identity, PID ═ PID₁,PID₂,…PID_n},(PPK,PSK)＝{(PPK₁,PSK₁),(PPK₂,PSK₂),…(PPK_n,PSK_n)}，j＝{1,2…n}；

S2: EV selects a pseudo-identity PID from the pseudo-identity set and the key pair set respectively_iAnd a corresponding key pair (PPK)_i,PSK_i) To calculate a temporary token TOK for RSU authentication identity_i，i＝{1,2…n}

S3: the EV sends a charging request to the RSU, wherein the charging request comprises a temporary token TOK_iAnd by a temporary session key K_EV,RSUEncrypted pseudo-identity information and key pair information;

s4: the RSU calculates a temporary session key K between the RSU and the EV after receiving the charging request_EV,RSUThe charging request is decrypted by the pseudo identity information and the key pair information;

s5: RSU based on received TOK_iAnd judging whether the EV is legal or not by the pseudo identity information and the key pair information obtained after decryptionIf yes, go to S7, otherwise, go to S6;

s6: the RSU refuses the charging service;

s7: RSU calculates seed key alpha of temporary session key between EV and charging panel CP, binds calculated seed key alpha with false identity information of EV and passes K_RSU,CPSending the encrypted seed key to the CP, binding the calculated seed key with the pseudo identity information of the EV and passing through the K_EV,RSUEncrypted and sent to the corresponding EV, wherein K_RSU,CPRepresenting a temporary session symmetric key negotiated in advance between the RSU and the CP;

s8: EV passage K_EV,RSUDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iAnd use a one-time session key alpha_iGenerating an authentication code and transmitting the authentication code to the CP;

s9: CP through K_RSU,CPDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iVerifying the authentication code sent by the EV based on the one-time session key, and providing charging service to the EV after the verification is passed;

s10: CP totaling as PID_iThe marked EV provides the total electric energy, and sends corresponding total electric energy information to the RSU;

s11: the RSU generates PID according to the received total electric energy information_iBilling the identified EV and sending the bill to the corresponding EV;

s12: the RSU, upon receiving the EV's payment message, checks the bill and returns an acknowledgement message.

It should be noted that, before step S1, a step of initializing the system may be further included, and a specific process may be shown in fig. 3, where initializing the system includes the following sub-steps:

s011: the trusted center TA generates a system public parameter and a public key PK of the TA according to a preset safety parameter_TAAnd a private key SK_TA。

Through step S011, the TA completes initialization. The system common parameters in this embodiment include two large prime numbers p and q, and an elliptic curve E:y²＝x³+ ax + b mod P, a cyclic group G of order q, a generator P of the cyclic group G, and a one-way hash function of the system. The relationship PK between the public key and the private key of the TA is satisfied in the embodiment_TA＝SK_TA·P。

S012: the CSP sends its own ID information to TA_CSPRegistration is requested.

S013: TA generates CSP public key PK after confirming CSP sent identity information is legal_CSPAnd a private key SK_CSPAnd generates the CSP public key certificate Cert by using the TA private key_CSPAnd the system public parameter, PK, is connected through a secure channel_CSP、SK_CSPAnd Cert_CSPIs sent to the CSP and then sent to the CSP,

representation through SK_TAFor ID_CSPAnd PK_CSPAnd (4) encrypting the generated signature.

Public key certificate Cert_CSPIncluding identity information ID of CSP_CSPCSP public key PK_CSPAnd signatures

It should be noted that TA may select a random number s_CSPPrivate key SK as CSP_CSPWherein

Means that positive integers are modulo-q operated and according to the formula PK_CSP＝s_CSPP calculates the public key PK of CSP_CSP。

S014: CSP generates corresponding ID for each CP in its management range_CPThen using the private key SK of CSP_CSPFor ID_CPGenerating signatures

And sends the signature to the corresponding CP through the secure channel.

The CSP completes initialization through steps S012 to S104, and this is explained as followsExamples of the embodiments

S015: RSU sends self identity information ID to TA_RSURegistration is requested.

S016: the TA generates a public key PK of the RSU after confirming that the identity information sent by the RSU is legal_RSUPrivate key SK_RSUAnd public key certificate Cert of RSU_RSUAnd the system public parameter, PK, is connected through a secure channel_RSU、SK_RSUAnd Cert_RSUIs sent to the RSU and then sent to the RSU,

representation through SK_TAFor ID_RSUAnd PK_RSUAnd (4) encrypting the generated signature.

Specifically, the TA may select a random number s after confirming that the identity information of the RSU is legal_RSUSK as private key of RSU_RSUWherein

And according to formula PK_RSU＝s_RSUP calculates the public key PK of the RSU_RSU。

S017: the RSU negotiates temporary session symmetric keys for ensuring secure communication with the CPs within the communication range of the RSU, and stores the negotiated temporary session symmetric keys locally for subsequent secure communication respectively.

Through steps S015 to S017, the RSU completes initialization.

S018: EV needing charging service sends its own real identity information RID to TA_EVRegistration is requested.

S019: the TA generates a public key PK of the EV after confirming that the real identity information of the EV is legal_EVPrivate key SK_EVAnd the public key certificate Cert of the EV_EVAnd generates a set PID consisting of n pseudo-identities for the EV according to the real identity of the EV,

representation through SK_TAFor RID_EVAnd PK_EVAnd (4) encrypting the generated signature.

Specifically, the TA may select a random number s after confirming that the identity information of the EV is valid_EVPrivate key SK as EV_EVWherein

And according to formula PK_EV＝s_EVP calculates the EV's public key PK_EV。

Jth pseudo identity PID of EV in this embodiment_jUsing a pseudo-identity tuple (PID)_j，1，PID_j,2) And (4) showing.

I.e. PID_j＝(PID_j，1，PID_j,2),PID_j，1And PID_j,2PID representing a pseudo-identity_jCan be calculated by formula PID in step S019_j,1＝d_jP compute meta-component PID_j，1By the formula

Compute meta-component PID_j,2，d_jRandom number representing TA selection, H1 representing the first one-way hash function of the system, H₁(d_j·PK_TA) Representing d by a first one-way hash function_j·PK_TAAnd performing conversion processing.

S020: TA uses its private key SK_TATrue identity RID for EV_EVSigning with corresponding pseudo identity PID to obtain

S021: TA sends the system public parameter, PK through the secure channel_EV、SK_EV、Cert_EVPID and

and sending the information to the EV.

S022: and the EV stores a pseudo identity set PID corresponding to the real identity of the EV in a local tamper-proof equipment unit.

The EV completes initialization in step S018 to step S022.

Each EV requiring charging service registration needs to be performed with the CSP, and a specific registration process can be shown in fig. 4. generally, an EV sends a registration request to the CSP before first use, where the registration request is also referred to as a request for subscribing to charging service.

That is, in the present embodiment, after the system initialization step and before step S1, the method further includes the following steps:

s031: EV sends a request M for subscribing charging service to CSP₁Wherein

t1 denotes EV Generation subscription charging service request M₁Time stamps generated.

It should be noted that, in order to ensure that the pseudo identity of the EV is issued by the TA and the association between the real identity and the pseudo identity is between the real identity and the pseudo identity, the subscription charging service request further includes a signature sent by the TA to the EV using its private key to the real identity and the pseudo identity of the EV when the EV registers with the TA.

S032: CSP receives a request M for subscribing charging service sent by EV during registration₁Then, use private key SK_CSPDecrypt the message, if not, abort the session, otherwise check the timestamp t1 and use the public key PK of the TA_TAChecking signatures

If not, the session is aborted, otherwise the charging service registration information of the EV is recorded in the database and step S033 is performed.

S033: the CSP generates n pairs of key pairs for authenticating the charging service for the EV, and generates a message M of the key pairs for authenticating the charging service using the set of key pairs₂And M is₂Is sent to the EV, wherein

t2 denotes when the CSP generates the message M2 for authenticating the key pair of the charging serviceThe time stamp that is generated is,

private key SK representing use of CSP_CSPThe generated signature is encrypted with a set of generated key components not related to the pseudo-identity PPK, a set of generated key components related to the pseudo-identity PSK and a time stamp t 2.

Public key pair PPK, PSK, t2 and representing the use of EV

And (4) encrypting.

A flow chart of EV access to charging service can be seen in fig. 5, and it should be noted that, in step S033, the CSP can use the formula PPK_jCalculating key components independent of false identity (Rp), and performing PSK (phase Shift keying) by using formula_j＝r+H₂(PID_j,PPK_j)·SK_CSPmod q computes a key component, r, associated with the pseudo-identity_jThe random number representing the CSP's choice is,

H₂a second one-way hash function, H, representing the system₂(PID_j,PPK_j) Representing PID pairs using a second one-way hash function_jAnd PPK_jFor the conversion process, it should be noted that mod represents a modulo operation.

S034: EV uses its private key SK_EVTo the received message M₂Decrypting, if not, terminating the session, otherwise, checking the timestamp t2 and using the CSP's public key PK_CSPChecking signatures

If not, aborting the session, otherwise storing a set of key pairs (PPK, PSK) for the authentication service on the tamper resistant device unit of the vehicle.

It should be noted that, in the present embodiment, theThe RSU will broadcast its credentials, which can be received by both EVs and CPs within its communication range. Certificate broadcast by RSU

Indicating the use of SK_TAFor ID_RSUAnd PPK_RSUEncrypted signature, RSU broadcast certificate including ID_RSU、PPK_RSUAnd

EV receives certificate Cert_RSUPublic key PK of TA can be used later_TAThe certificate is verified for correctness. If the certificate is incorrect, the session is aborted, otherwise, the EV obtains the public key PK of the RSU from the certificate_RSU。

The step of the RSU negotiating the temporary session symmetric key with the CP includes:

s041: the CP verifies the correctness of the certificate broadcasted by the RSU after receiving the certificate, and extracts the public key PK of the RSU from the certificate after the verification is passed_RSUAnd selecting a random number mu to calculate K_CPAnd K_RSU,CP，K_CP＝μ·P，K_RSU,CP＝μ·PK_RSUWherein

S042: CP sending message

To the RSU, where nonce denotes the random number selected by the CP.

Wherein,

indicates the use of K_RSU,CPAnd encrypting the nonce.

S043: RSU passes through CSP public key PK after receiving message sent by CP_CSPVerifying receiptWhether the signature in the incoming message is signed by the CSP, e.g., by the derived K_CPAnd formula K_RSU,CP＝SK_RSU·K_CPCalculate K_RSU,CPAnd using the calculated K_RSU,CPDecrypting the message to obtain a nonce and sending the message

Feeding the CP;

s044: CP uses K_RSU,CPAnd decrypting the received message, and judging whether the decrypted message is equal to nonce +1, if so, successfully negotiating the temporary session symmetric key between the RSU and the CP, otherwise, failing to negotiate the temporary session symmetric key between the RSU and the CP.

In order to ensure the communication security, the RSU and the CP may periodically update the temporary session symmetric key between the RSU and the CP.

It should be noted that the EV obtains the public key PK of the RSU from the certificate broadcast by the RSU_RSUCan then be based on formula K_EV,RSU＝x·PK_RSUCalculating a temporary session key K for secure communication with an RSU_EV,RSUX represents a random number for EV selection,

temporary token TOK in this embodiment_iComprises TOK_i,1And TOK_i,2Step S2 includes: EV passing formula TOK_i,1Calculating TOK as x.P_i,1And by the formula TOK_i,2＝PSK_i+H₃(PID_i,PPK_i,TOK_i,1Request, t 3). x mod q to calculate TOK_i,2，H₃A third one-way hash function representing the system, request representing charging parameter information, such as battery and coil type information and charging rate information of the EV, and t3 representing the TOK calculated by the EV_iTime stamps generated.

Step S3 includes: EV sends charging request M to RSU₃，

Step S4 includes: RSU by formula K_EV,RSU＝SK_RSU·TOK_i,1Calculate a temporary session key K between it and the EV_EV,RSUAnd decrypts the received M using the temporary session key₃Get { PID_i,PPK_i,t3}。

Step S5 includes: the RSU checks the timestamp t3 based on the received TOK_i,1、TOK_i,2And decrypted to obtain { PID_i,PPK_iJudging whether the equation for verifying the identity validity is established, if so, going to S7, otherwise, going to S6, wherein the equation for verifying the identity validity is as follows:

TOK_i,2·P＝PPK_i+H₂(PID_i,PPK_i)·PK_CSP+H₃(PID_i,PPK_i,TOK_i,1,request,t3)·TOK_i,1。

it should be noted that step S7 in the present embodiment may include the following steps:

s71: the RSU selects a random number alpha as a seed key for computing the temporary session key between the EV and the CP, wherein,

and calculate

t4 denotes that RSU is calculating RES₁And RES₂Time-generated time stamps, RES₁Indicates the use of K_EV,RSUTo PID_iAlpha and t4 are encrypted to obtain a message, RES₂Representation to PID_iα, and t 4.

S72: RSU sends message M₄To EV and send message M₅For each CP controlled by the RSU, where M₄＝{RES₁,RES₂,t4}，

t5 denotes the RSU generation message M₅Time stamps generated.

Wherein,

representing the use of the private Key SK_RSUTo PID_iAlpha and t5,

indicates the use of K_EV,RSUTo PID_iα, t5 and

and (4) encrypting the obtained message.

RSU sends message M₄Sends to EV and sends message M₅After sending to the CP, the EV and CP are based on message M₄And message M₅An authentication process is implemented. Specifically, the authentication between the EV and the CP includes the following procedures:

EV receives message M from RSU₄Check the timestamp t4 and use the temporary session key K_EV,RSUDecrypting message RES₁To obtain (PID)_iα, t4) and is obtained from decryption (PID)_i,. alpha., t4) to calculate RES'₂＝HMACK_EV,RSU(PID_iα, t4) and RES'₂Comparing with the received RES2, if they are not equal, the EV aborts the session; otherwise, the EV obtains a seed key alpha for calculating the one-time session key for authentication of the EV and the CP;

each CP receives the message from RSU, uses the symmetric key pre-distributed by TA to decrypt the message, if not, stops the conversation, otherwise, checks if the signature is correct, if the signature is incorrect, stops the conversation, otherwise, uses the fourth one-way hash function of the system to calculate to obtain the one-time conversation key alpha_i。

Specifically, when the electric vehicle passes through the ith charging pad CP, an AuthCode having a random number r is transmitted to prove that the electric vehicle passes the verification of the RSU, where AuthCode is H₅(α_iR), after verification of the CP, the CP authenticates it by sending an acknowledgement code ConfCode, wherein ConfCode is H₅(α_i,r，1)，H₅A fifth one-way hash function representing the system, once authentication is complete, the CP will open to charge the EV.

Preferably, the method provided by this embodiment further includes the following steps:

if the RSU does not receive the payment message of the EV within the preset time period, the pseudo identity information of the EV which does not pay the charging service fee successfully is recorded and sent to the TA, the TA calculates the real identity corresponding to the pseudo identity information after receiving the pseudo identity information of the EV sent by the RSU, and publishes the real identity of the EV, and the tracing of the identity of the illegal action is realized based on privacy protection.

It should be noted that, with the solution provided in this embodiment, after the EV is successfully registered on the CSP, the EV does not need to perform information interaction with the CSP, that is, the EV does not need to pass the authentication of the CSP every time the EV subsequently initiates a charging service request, so that the data throughput of the CSP is reduced, and even if the CSP goes wrong or goes offline, the EV can obtain the charging service.

After the EV charging of the electric vehicle is finished, each charging plate CP changes the EV charging into a charging state according to PID_iThe electric energy provided by the identified EV is sent to a roadside unit RSU, and after the RSU receives the information of the charging panel, the total number of the electric energy is counted as PID_iGenerating a corresponding bill by the electric energy provided by the identified EV and sending the bill to the EV; the EV completes payment immediately after receiving the bill, and the specific flow can be seen in fig. 6.

Specifically, each CP can combine messages

Sent to the RSU, where PIDi is the pseudo-identity of the EV,

and

PID respectively representing the ith charging plate as a pseudo identity_iStart time and end time of EV charging, E_piPID for indicating the ith charging plate as a false identity_iT6 denotes that the CP is being produced at the current timeA time stamp of the generation.

RSU receives message M sent by charging panel₆Using a pre-distributed symmetric key K_RSU,CPIs decrypted to obtain

Will be calculated

Is compared with the received value of

Comparing, if not, stopping conversation, otherwise, RSU counting to obtain N charging plates as false ID PID_iElectric energy supplied by the EV

The RSU calculates the pseudo-identity PID according to the current electricity price_iThe EV to be paid charges account, generates a bill message

Sent to the EV, t7 represents the timestamp generated by the RSU at the current time.

EV received message M₇Thereafter, the key K is used_RSU,CPDecrypting messages and verifying results of calculations

Is compared with the received value of

If not, discarding the message; otherwise, the EV returns a payment message

To the RSU, where coin represents the proof of payment, t8 represents the timestamp that the EV generated at the current time.

RSU receives EV payment message M₇Thereafter, the key K is used_RSU,CPDecrypt the message andjudgment of

And

whether the value is correct. If the payment is correct, the RSU returns a payment confirmation message representing that the EV payment is successful

Wherein succ represents payment success; otherwise, the EV is not paid successfully, it is recorded by the RSU, and t9 represents the timestamp generated when the RSU returns the payment confirmation message.

And when the charging of the electric vehicle EV is finished, the payment is not finished, and the RSU records the false identity of the electric vehicle which is not paid successfully. At intervals (e.g., one week), the recorded list is sent to the trust center TA, which reveals and publishes the true identity of the EV.

Specifically, the RSU may list the pseudo-identities of EVs that have not successfully paid for charging services

Sending to TA, receiving RSU message M by trusted center₁₀Check the timestamp t10, and calculate

Revealing the true identity of the EV to penalize the EV with improper behavior, t10 representing the timestamp generated when the RSU sends the list of pseudo-identities, the flow of identity tracing can be seen in fig. 7.

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.

Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal (such as a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present invention.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. An electric vehicle charging service method capable of protecting privacy is characterized by comprising the following steps:

s1: the electric vehicle EV verifies the correctness of the certificate after receiving the certificate broadcasted by the roadside unit RSU, and extracts the public key PK of the RSU from the certificate after the verification is passed_RSUAnd according to the public key PK_RSUCalculating a temporary session key K of the EV and the RSU_EV,RSU(ii) a The local database of the EV is prestored with a set PID (proportion integration differentiation) formed by n pseudo identities which are distributed by a trusted center TA and correspond to the real identity of the EV, and a set (PPK, PSK) formed by a key pair which is distributed by a charging service provider CSP for each pseudo identity in the pseudo identity set PID and used for authenticating the charging service, wherein each key pair comprises a component PPK_jAnd component PSK_j，PPK_jRepresenting key components independent of pseudo-identity, PSK_jRepresenting a key component associated with a pseudo-identity, PID ═ PID₁,PID₂,…,PID_n}，(PPK,PSK)＝{(PPK₁,PSK₁),(PPK₂,PSK₂),…,(PPK_n,PSK_n)}，j＝{1,2,…,n}；

S2: EV selects a pseudo-identity PID from the pseudo-identity set and the key pair set respectively_iAnd a corresponding key pair (PPK)_i,PSK_i) To calculate a temporary token TOK for RSU authentication identity_i，i＝{1,2,…,n}；

S3: the EV sends a charging request to the RSU, wherein the charging request comprises a temporary token TOK_iAnd by a temporary session key K_EV,RSUEncrypted pseudo-identity information and key pair information;

s4: the RSU calculates a temporary session key K between the RSU and the EV after receiving the charging request_EV,RSUThe charging request is decrypted by the pseudo identity information and the key pair information;

s5: RSU based on received TOK_iJudging whether the EV is a legal authorized user or not by the decrypted pseudo-identity information and the decrypted key pair information, if so, turning to S7, and otherwise, turning to S6;

s6: the RSU refuses the charging service;

s7: RSU calculates seed key alpha of temporary session key between EV and charging panel CP, binds calculated seed key alpha with false identity information of EV and passes K_RSU,CPSending the encrypted seed key to the CP, binding the calculated seed key with the pseudo identity information of the EV and passing through the K_EV,RSUEncrypted and sent to the corresponding EV, wherein K_RSU,CPRepresenting a temporary session symmetric key negotiated in advance between the RSU and the CP;

s8: EV passage K_EV,RSUDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iAnd use a one-time session key alpha_iGenerating an authentication code and transmitting the authentication code to the CP;

s9: CP through K_RSU,CPDecrypting the message to obtain a seed key alpha, and generating a one-time session key alpha according to the seed key_iVerifying the authentication code sent by the EV based on the one-time session key, and providing charging service to the EV after the verification is passed;

s10: CP totaling as PID_iThe marked EV provides the total electric energy, and sends corresponding total electric energy information to the RSU;

s11: the RSU generates PID according to the received total electric energy information_iBilling for the identified EV and issuing the billSending the data to a corresponding EV;

s12: the RSU, upon receiving the EV's payment message, checks the bill and returns an acknowledgement message.

2. The privacy-preserving electric vehicle charging service method as claimed in claim 1, further comprising a step of initializing a system before step S1, wherein the step of initializing the system includes the sub-steps of:

s011: the trusted center TA generates a system public parameter and a public key PK of the TA according to a preset safety parameter_TAAnd a private key SK_TA；

S012: the CSP sends its own ID information to TA_CSPRequesting registration;

s013: TA generates CSP public key PK after confirming CSP sent identity information is legal_CSPAnd a private key SK_CSPAnd generates the CSP public key certificate Cert by using the TA private key_CSPAnd the system public parameter, PK, is connected through a secure channel_CSP、SK_CSPAnd Cert_CSPIs sent to the CSP and then sent to the CSP,

representation through SK_TAFor ID_CSPAnd PK_CSPA signature generated after encryption;

s014: CSP generates corresponding ID for each CP in its management range_CPThen using the private key SK of CSP_CSPFor ID_CPGenerating signatures

And sending the signature to a corresponding CP through a secure channel;

s015: RSU sends self identity information ID to TA_RSURequesting registration;

s016: the TA generates a public key PK of the RSU after confirming that the identity information sent by the RSU is legal_RSUPrivate key SK_RSUAnd public key certificate Cert of RSU_RSUAnd the system public parameter, PK, is connected through a secure channel_RSU、SK_RSUAnd Cert_RSUIs sent to the RSU and then sent to the RSU,

representation through SK_TAFor ID_RSUAnd PK_RSUA signature generated after encryption;

s017: the RSU negotiates a temporary session symmetric key for ensuring safe communication with the CP in the communication range of the RSU, and stores the negotiated temporary session symmetric key locally for subsequent safe communication;

s018: EV needing charging service sends its own real identity information RID to TA_EVRequesting registration;

s019: the TA generates a public key PK of the EV after confirming that the real identity information of the EV is legal_EVPrivate key SK_EVAnd the public key certificate Cert of the EV_EVAnd generates a set PID consisting of n pseudo-identities for the EV according to the real identity of the EV,

representation through SK_TAFor RID_EVAnd PK_EVA signature generated after encryption;

s020: TA uses its private key SK_TATrue identity RID for EV_EVSigning with corresponding pseudo identity PID to obtain

S021: TA sends the system public parameter, PK through the secure channel_EV、SK_EV、Cert_EVPID and

sending the information to the EV;

s022: and the EV stores a pseudo identity set PID corresponding to the real identity of the EV in a local tamper-proof equipment unit.

3. The privacy-preserving electric vehicle charging service method as claimed in claim 2, wherein the system public parameters include a generator P of a system cycle group and a one-way hash function of the system;

PID_j＝(PID_j，1，PID_j,2),PID_j，1and PID_j,2PID representing a pseudo-identity_jIs calculated by the formula PID in step S019_j,1＝d_jP compute meta-component PID_j，1By the formula

Compute meta-component PID_j,2，d_jRandom number indicating TA selection, H₁A first one-way hash function representing a system.

4. The privacy-preserving electric vehicle charging service method as claimed in claim 3, further comprising, after the system initialization step and before step S1:

s031: EV sends a request M for subscribing charging service to CSP₁Wherein

t1 denotes EV Generation subscription charging service request M₁The time stamp generated at the time of the clock,

s032: CSP receives a request M for subscribing charging service sent by EV during registration₁Then, use private key SK_CSPDecrypt the message, if not, abort the session, otherwise check the timestamp t1 and use the public key PK of the TA_TAChecking signatures

If not, stopping the session, otherwise, recording the charging service registration information of the EV in a database and executing the step S033;

s033: the CSP generates n pairs of key pairs for authenticating the charging service for the EV, and generates a message M of the key pairs for authenticating the charging service using the set of key pairs₂And M is₂Is sent to the EV, wherein

t2 denotes a message M that the CSP generates a key pair for authenticating the charging service₂A time stamp generated;

private key SK representing use of CSP_CSPEncrypting the generated signature on a set of generated key components (PPK) which are not related to the pseudo identity, a set of generated key components (PSK) which are related to the pseudo identity and a time stamp t 2;

s034: EV uses its private key SK_EVTo the received message M₂Decrypting, if not, terminating the session, otherwise, checking the timestamp t2 and using the CSP's public key PK_CSPChecking signatures

If not, aborting the session, otherwise storing a set of key pairs (PPK, PSK) for the authentication service on the tamper resistant device unit of the vehicle.

5. The privacy-preserving electric vehicle charging service method according to claim 4, wherein the step S033 includes:

CSP by formula PPK_j＝r_jP calculates the key components independent of the pseudo-identity and passes the formula PSK_j＝r_j+H₂(PID_j,PPK_j)·SK_CSPmod q computes a key component, r, associated with the pseudo-identity_jRandom number representing CSP selection，H₂And a second one-way hash function representing the system, and q is a system public parameter.

6. The privacy-preserving electric vehicle charging service method as claimed in claim 3, wherein the step of the RSU negotiating the temporary session symmetric key with the CP includes:

s041: the CP verifies the correctness of the certificate broadcasted by the RSU after receiving the certificate, and extracts the public key PK of the RSU from the certificate after the verification is passed_RSUAnd selecting a random number mu to calculate K_CPAnd K_RSU,CP，K_CP＝μ·P，K_RSU,CP＝μ·PK_RSU；

S042: CP sending message

Giving RSU, wherein nonces represent random numbers selected by CP;

indicates the use of K_RSU,CPEncrypting the nonce;

s043: RSU passes through CSP public key PK after receiving message sent by CP_CSPVerifying if the signature in the received message was signed by the CSP, e.g., by obtaining K_CPAnd formula K_RSU,CP＝SK_RSU·K_CPCalculate K_RSU,CPAnd using the calculated K_RSU,CPDecrypting the message to obtain a nonce and sending the message

Feeding the CP;

s044: CP uses K_RSU,CPAnd decrypting the received message, and judging whether the decrypted message is equal to nonce +1, if so, successfully negotiating the temporary session symmetric key between the RSU and the CP, otherwise, failing to negotiate the temporary session symmetric key between the RSU and the CP.

7. The privacy-preserving electric vehicle charging service method as claimed in claim 6, wherein the RSU and the CP periodically update the temporary session symmetric key between the RSU and the CP.

8. The privacy-preserving electric vehicle charging service method as claimed in any one of claims 3 to 7, wherein the step S1 includes: EV according to formula K_EV,RSU＝x·PK_RSUCalculating a temporary session key K for secure communication with an RSU_EV,RSUX represents a random number for EV selection;

temporary token TOK_iComprises TOK_i,1And TOK_i,2Step S2 includes: EV passing formula TOK_i,1Calculating TOK as x.P_i,1And by the formula TOK_i,2＝PSK_i+H₃(PID_i,PPK_i,TOK_i,1Request, t 3). x mod q to calculate TOK_i,2，H₃A third one-way hash function representing the system, request representing charging parameter information, and t3 representing EV calculation TOK_iA time stamp generated;

step S3 includes: EV sends charging request M to RSU₃，

Step S4 includes: RSU by formula K_EV,RSU＝SK_RSU·TOK_i,1Calculate a temporary session key K between it and the EV_EV,RSUAnd decrypts the received M using the temporary session key₃Get { PID_i,PPK_i,t3}；

Step S5 includes: the RSU checks the timestamp t3 based on the received TOK_i,1、TOK_i,2And decrypted to obtain { PID_i,PPK_iJudging whether the equation for verifying the identity validity is established, if so, going to S7, otherwise, going to S6, wherein the equation for verifying the identity validity is as follows:

TOK_i,2·P＝PPK_i+H₂(PID_i,PPK_i)·PK_CSP+H₃(PID_i,PPK_i,TOK_i,1,request,t3)·TOK_i,1。

9. the privacy-preserving electric vehicle charging service method as claimed in any one of claims 1 to 7, wherein the step S7 includes:

s71: the RSU selects a random number alpha as a seed key for calculating a temporary session key between the EV and the CP, and calculates

RES₂＝HMACK_EV,RSU(PID_iα, t4), t4 represents the time stamp generated by the RSU when calculating RES1 and RES2, RES₁Indicates the use of K_EV,RSUTo PID_iAlpha and t4 are encrypted to obtain a message, RES₂Representation to PID_iA, and t 4;

s72: RSU sends message M₄To EV and send message M₅For each CP controlled by the RSU, where M₄＝{RES₁,RES₂,t4}，

t5 denotes the RSU generation message M₅A time stamp generated;

representing the use of the private Key SK_RSUTo PID_iA and t 5.

10. The privacy-preserving electric vehicle charging service method as claimed in any one of claims 1 to 7, further comprising:

if the RSU does not receive the payment message of the EV within the preset time period, the pseudo identity information of the EV which does not pay the charging service fee successfully is recorded and sent to the TA, and the TA calculates the real identity corresponding to the pseudo identity information after receiving the pseudo identity information of the EV sent by the RSU and publishes the real identity of the EV.

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