A smart grid real-time processing system and method with privacy protection

Abstract

The present invention relates to the field of smart grid technology, and in particular to a smart grid real-time processing system and method with privacy protection. In the context of smart grid, based on fog computing, coding, homomorphic encryption and other technologies, a multifunctional and efficient privacy protection scheme is constructed. Specifically, through the smart grid real-time processing system of the present invention, an electric power service provider can not only obtain the total electricity consumption of registered users, but also charge users based on real-time prices. When a user questions a bill sent by the electric power service provider, the user can initiate an arbitration request to an arbitration center, which will resolve the dispute. At the same time, the user can also initiate a query request to the electric power service company to inquire about the electricity charges for a period of time, thereby solving the technical problem of integrating multiple functions that cannot be achieved in existing schemes.

Description

Technical Field

[0001] The present invention relates to the technical field of smart grids, and in particular to a smart grid real-time processing system and method with privacy protection. Background Art

[0002] In a smart grid, smart meters are responsible for generating real-time electricity consumption data for users and reporting the data to power service providers at regular intervals (for example, every 15 minutes). Power service providers analyze the data to predict electricity demand and adjust electricity generation and distribution, thereby significantly improving the reliability, flexibility and efficiency of the power system.

[0003] As a supplement to the cloud computing model, fog computing extends computing power to the edge of the network, enabling users to perform computing, communication and storage locally. The advantages of fog computing, such as low latency and location awareness, meet the latency-sensitive requirements of smart grid applications. By applying fog computing technology to smart grids, the real-time performance and service quality of smart grid systems can be improved.

[0004] Although the smart grid based on fog computing has a bright future, it still faces serious challenges in terms of privacy and security. Specifically, adversaries can infer users' lifestyles, behavioral habits, family size and other private information by analyzing users' real-time electricity consumption data, and carry out certain illegal activities based on this information; at the same time, they can also pose a serious threat to the stability of smart grids by actively attacking (for example, tampering, forging, replaying, etc.) the data transmitted in the communication channel.

[0005] In existing privacy protection schemes, power service providers can only obtain the total power consumption of registered users in the grid coverage area, and then predict, generate and distribute power based on the total power consumption. Few schemes consider implementing more diverse functions under the premise of protecting user privacy, such as providing privacy-protected billing functions. In those schemes that consider billing, power service providers usually only charge users based on fixed prices. With the rapid development of smart grids, the above charging methods are no longer applicable. Countries such as Sweden have required power service providers to provide users with hourly contracts. The fundamental reason is that fixed prices cannot reflect the relationship between power supply and demand, resulting in power service providers being unable to adjust in time when power demand fluctuates, resulting in a huge waste of resources. Strategies based on real-time prices can guide users to change their consumption patterns according to dynamic prices and improve resource utilization efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide a smart grid real-time processing system and method with privacy protection, aiming to provide a privacy protection solution with electricity statistics, real-time billing and dispute arbitration functions based on fog computing, coding and homomorphic encryption technologies in the context of smart grid.

[0007] To achieve the above object, the present invention provides a smart grid real-time processing system with privacy protection, including a root key generation center RKG, a smart meter SM ij , fog node FN i , arbitration center AC and power service provider SP, the root key generation center RKG is responsible for generating system public parameters, the smart meter SM ij Responsible for generating real-time electricity consumption data of users and sending the encrypted electricity consumption data to the corresponding fog node FN regularly i , the fog node FN i It is responsible for verifying the validity of the ciphertext and aggregating all valid ciphertexts and forwarding them to the arbitration center AC. The arbitration center AC is responsible for pre-decryption and arbitration of disputes. The power service provider SP is responsible for collecting the total electricity consumption of all users in the grid coverage area and charging them in real time.

[0008] The present invention also provides a smart grid real-time processing method with privacy protection, comprising the following steps:

[0009] The root key generation center RKG generates the initial parameters of the system;

[0010] Each entity in the system registers and obtains a key;

[0011] Smart MeterSM ij Encrypt the power consumption data and send it to the corresponding fog node FN i ;

[0012] The fog node FN i Perform aggregate verification;

[0013] The arbitration center AC checks the validity of the report and performs pre-decryption;

[0014] Real-time electricity billing;

[0015] If any dispute arises regarding electricity charges, it will be handled through arbitration.

[0016] The process of generating the initial system parameters by the root key generation center RKG includes the following steps:

[0017] The root key generation center RKG generates a bilinear map e:G×G→G τ , where G,G τ are two multiplicative cyclic groups of order q, and g is a generator of G;

[0018] The root key generation center RKG selects a secure cryptographic hash function H:{0,1} * →G.

[0019] The key includes a private key and a public key. The root key generation center RKG randomly selects a private key for each registered entity and calculates and generates a corresponding public key.

[0020] Among them, in the fog node FN i During the aggregation verification process, after receiving the data sent by all smart meters in the coverage area, the fog node FN i First, the validity of all reports is checked by running a batch verification algorithm, and then all valid ciphertexts are aggregated and sent to the arbitration center AC.

[0021] Among them, in the fog node FN i During the aggregation verification process, after receiving the data sent by all smart meters in the coverage area, the fog node FN i First, the validity of all reports is checked by running a batch verification algorithm, and then all valid ciphertexts are aggregated and sent to the arbitration center AC.

[0022] In the process of the arbitration center AC checking the validity of the report and performing pre-decryption, the arbitration center AC first checks the validity of all reports by running a batch verification algorithm, performs pre-decryption after passing the verification, and sends the decrypted results to the power service provider SP.

[0023] The process of real-time electricity billing includes the following steps:

[0024] Fog Node FN i Aggregate electricity fee ciphertext;

[0025] The arbitration center AC pre-decrypts the fog node FN i Aggregated electricity fee ciphertext;

[0026] The power service provider SP performs final decryption on the result obtained after pre-decryption by the arbitration center AC to obtain the user's electricity fee for a billing cycle.

[0027] The arbitration process includes the following steps:

[0028] Step 1: For the disputed electricity fee ciphertext (U ij ,V ij ), the arbitration center AC uses the private key x AC Pre-decrypt it to get the pre-decrypted ciphertext

[0029] Step 2: The power service provider SP uses the private key x SP calculate And generate a signature

[0030]

[0031] Where T SP is the current timestamp, used to defend against replay attacks, ID SP is the identity of the electricity service provider SP, Bil is the disputed electricity bill, and || is a concatenation symbol;

[0032] Step 3: The power service provider SP will (σ SP ,ID SP ,W,Bill,T SP ,pk SP ) sent to the arbitration center AC;

[0033] Step 4: The arbitration center AC checks the validity of the report by checking whether the following equation holds:

[0034] e(σ SP ,g)=e(H(ID SP ||W||Bill||T SP ),pk SP );

[0035] Step 5: If the report is valid, the arbitration center AC calculates In getting Then, using the pollard lambda method, the arbitration center AC can obtain Among them, p m The electricity price for the mth period is then compared between the bills sent by the user and the electricity service provider SP, and the arbitration center AC conducts arbitration effectively.

[0036] The present invention provides a smart grid real-time processing system and method with privacy protection. In the context of smart grid, based on fog computing, coding, homomorphic encryption and other technologies, a multifunctional and efficient privacy protection scheme is constructed. Specifically, through the smart grid real-time processing system of the present invention, the power service provider SP can not only obtain the total electricity consumption of registered users, but also charge users based on real-time prices. When the user has doubts about the bill sent by the power service provider SP, the user can initiate an arbitration request to the arbitration center AC, and the arbitration center AC will resolve the dispute. At the same time, the user can also initiate a query request to the power service provider SP to query the electricity charges for a period of time, which solves the technical problem of integrating multiple functions that cannot be achieved in existing solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a system architecture diagram of a smart grid real-time processing system with privacy protection of the present invention.

[0039] Figure 2 It is a flow chart of a smart grid real-time processing method with privacy protection according to the present invention. DETAILED DESCRIPTION

[0040] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0041] Please refer to Table 1 for some nouns or terms used in the examples of the present invention:

[0042] Table 1. Table of terms and explanations

[0043]

[0044]

[0045] See also Figure 1 The present invention proposes a smart grid real-time processing system with privacy protection, which specifically includes five types of entities: root key generation center RKG, smart meter SM ij , fog node FN i , arbitration center AC and electricity service provider SP.

[0046] (1) Root Key Generation Center RKG: Responsible for generating system public parameters and generating and distributing public and private keys for entities when they register.

[0047] (2) Smart Meter SM ij : Responsible for generating real-time electricity consumption data of users and sending the encrypted electricity consumption data to the corresponding fog node FN regularly i .

[0048] (3) Fog Node FN i :After receiving the encrypted data sent by all smart meters in the coverage area, the fog node FNi First, the validity of the report is checked through batch verification, and all valid ciphertexts are aggregated and sent to the arbitration center AC. i Ability to store ciphertext data for billing purposes.

[0049] (4) Arbitration center AC: upon receiving the information from fog node FN i After the report is sent, the arbitration center AC first verifies the report, pre-decrypts it after passing the verification, and sends the decrypted result to the power service provider SP.

[0050] (5) Power service provider SP: Responsible for collecting the total electricity consumption of all users in the area covered by the power grid, making power forecasts based on the total electricity consumption, and making flexible adjustments to the generation and distribution of electricity. At the same time, the power service provider SP also charges users based on real-time prices.

[0051] For further information, see Figure 2 The present invention also provides a smart grid real-time processing method with privacy protection, comprising the following steps:

[0052] S1: The root key generation center RKG generates the initial parameters of the system;

[0053] S2: Each entity in the system registers and obtains a key;

[0054] S3: Smart MeterSM ij Encrypt the power consumption data and send it to the corresponding fog node FN i ;

[0055] S4: the fog node FN i Perform aggregate verification;

[0056] S5: The arbitration center AC checks the validity of the report and performs pre-decryption;

[0057] S6: Real-time electricity billing;

[0058] S7: If a dispute arises regarding electricity charges, it will be handled through arbitration.

[0059] The following is a further explanation based on the specific implementation steps:

[0060] S1: The root key generation center RKG generates the initial parameters of the system;

[0061] First, assume that the root key generation center RKG guides the entire system and is responsible for generating system parameters. The parameter generation process operates as follows:

[0062] (1) The root key generation center RKG generates a bilinear map e:G×G→G τ , where G,Gτ are two multiplicative cyclic groups of order q, and g is a generator of G.

[0063] (2) The root key generation center RKG selects a secure cryptographic hash function H: {0,1} * →G.

[0064] S2: Each entity in the system registers and obtains a key;

[0065] In this phase, the root key generation center RKG generates and distributes keys for each entity registered with the system. Specifically, the registration phase consists of the following steps:

[0066] S2.1: Smart MeterSM ij Registration: For each smart meterSM ij (i=1,2,…,k,j=1,2,…,n), the root key generation center RKG randomly selects an integer as its private key and calculate the corresponding public key

[0067] S2.2: Fog Node FN i Registration: For each fog node FN i (i=1,2,…,k), the root key generation center RKG randomly selects an integer as its private key and calculate the corresponding public key

[0068] S2.3: Registration of arbitration center AC: Root key generation center RKG randomly selects an integer as its private key and calculate the corresponding public key

[0069] S2.4: Power service provider SP: Root key generation center RKG randomly selects an integer as its private key and calculate the corresponding public key

[0070] After the above steps are completed, the root key generation center RKG secretly sends the private keys of all entities to them through a secure channel and calculates the public key Finally, the system parameters (G, G τ ,e,q,g,pk ij ,pk FNi ,pk AC ,pk SP ,PK,H).

[0071] S3: Smart MeterSM ij Encrypt the power consumption data and send it to the corresponding fog node FN i ;

[0072] Assume that a billing cycle contains t data reporting time slots (1, 2, ..., t). In time slot m (m = 1, 2, ..., t), the smart meter SM ij Generate l types of electricity consumption data And send it to the corresponding fog node FN i In order to protect the user's privacy information from being leaked, the smart meter SM ij Data needs to be encrypted before it is sent. The specific steps are as follows:

[0073] S3.1: Smart MeterSM ij Follow the steps below to convert the l-dimensional power consumption data Constructed as 1-dimensional data c ij,m :

[0074]

[0075] ξ=[log2(n)+z]·(lw),

[0076] λ=[log2(n)+z]·(w-1),

[0077]

[0078] Here, z is The maximum number of bits in a smart meter SM ij Randomly select integers Calculate c ij,m The ciphertext C ij,m :

[0079]

[0080] S3.2: Smart MeterSM ij Using private key x ij Sign the encrypted data:

[0081]

[0082] Here T ij,m is the current timestamp, used to defend against replay attacks, It is a smart meterSM ij identity identification.

[0083] S3.3: Smart MeterSM ij (ID SMij ,u ij,m ,v ij,m ,T ij,m ,σ ij,m ,pk ij ) is sent to the corresponding fog node FNi .

[0084] S4: the fog node FN i Perform aggregate verification;

[0085] S4.1: After receiving data from all smart meters in the coverage area, the fog node FN i The validity of all reports is checked by running a batch validation algorithm, i.e. checking the equation:

[0086]

[0087] Is it true? If the equation is true, it means that all reports are valid. Fog node FN i The verified ciphertext data is stored in Table 2.

[0088] Table 2 Ciphertext data storage table

[0089]

[0090] S4.2: Fog Node FN i Aggregate all valid ciphertexts to get aggregate ciphertext C i,m :

[0091]

[0092] S4.3: Fog Node FN i Utilizing private keys For the aggregate ciphertext C i,m To sign:

[0093]

[0094] here is the current timestamp, used to defend against replay attacks, It is the fog node FN i identity identification.

[0095] S4.4: Fog Node FN i Will Sent to the Arbitration Center AC.

[0096] S5: The arbitration center AC checks the validity of the report and performs pre-decryption;

[0097] S5.1: After receiving all fog nodes FN in the coverage area i After sending the data, the arbitration center AC checks the validity of all reports by running a batch verification algorithm, that is, checking the equation:

[0098]

[0099] If the equation holds, then all reports are valid.

[0100] S5.2: After checking its validity, the arbitration center AC uses its private key x AC Perform the following pre-decryption to obtain the pre-decrypted ciphertext C i ' ,m :

[0101]

[0102] S5.3: The arbitration center AC uses the private key x AC For the pre-decrypted ciphertext C i ' ,m To sign:

[0103]

[0104] here is the current timestamp, used to defend against replay attacks, ID AC It is the identity of the arbitration center AC.

[0105] S5.4: The Arbitration Centre AC will Sent to the electricity service provider SP.

[0106] S5.5: After receiving the data sent by the arbitration center AC, the power service provider SP checks the validity of the data by checking whether the following equation holds:

[0107]

[0108] S5.6: If the data is valid, the electricity service provider SP calculates: In getting Then, using the pollard lambda method, the power service provider SP can obtain the sum of the coded data Its specific form is: here It is the fog node FN i The total amount of data of the same type consumed by all users within the coverage area.

[0109] Obviously, the power service provider SP can obtain the total power consumption of registered users in the coverage area during the time period. Based on this data, the power service provider SP can reasonably control power generation and distribution, and then predict the power price p for the next time period. m+1 , and broadcast p before the next time period begins m+1 (Giving a specific pricing process is beyond the scope of the present invention.) Users can flexibly adjust their electricity usage patterns according to electricity prices at different time periods.

[0110] S6: Real-time electricity billing;

[0111] The billing process consists of three parts: 1) Fog Node FN i Aggregate electricity fee ciphertext, 2) arbitration center AC pre-decrypts fog node FN i Aggregated electricity fee ciphertext,3) The power service provider SP performs final decryption on the result obtained after pre-decryption by the arbitration center AC, and obtains the user's electricity fee in a billing cycle.

[0112] S6.1: Aggregation

[0113] S6.1.1: Fog Node FN i According to user ij The power ciphertext (u ij,m ,v ij,m ) and the electricity price p in the mth period m Calculate user u ij The electricity fee ciphertext for the mth period

[0114]

[0115] S6.1.2: Fog Node FN i Aggregate user u as follows ij Electricity fee ciphertext B in a billing cycle ij :

[0116]

[0117] S6.1.3: Fog Node FN i Using private key x FNi The electricity fee ciphertext B obtained after aggregation ij To sign:

[0118]

[0119] here is the current timestamp, used to defend against replay attacks, It is the fog node FN i identity identification.

[0120] S6.1.4: Fog Node FN i Will Sent to the Arbitration Center AC.

[0121] S6.2: Pre-decryption

[0122] S6.2.1: After receiving all fog nodes FN in the coverage area i After sending the data, the arbitration center AC checks the validity of all reports by running a batch validation, i.e. checking the equation:

[0123]

[0124] If the equation holds, then all reports are valid.

[0125] S6.2.2: After checking its validity, the arbitration center AC uses its private key x AC Perform the following pre-decryption to obtain the pre-decrypted ciphertext B ij′ :

[0126]

[0127] S6.2.3: The arbitration center AC uses the private key x AC For the pre-decrypted ciphertext B ij′ To sign:

[0128]

[0129] Here T AC' is the current timestamp, used to defend against replay attacks, ID AC It is the identity of the arbitration center AC.

[0130] S6.2.4: The Arbitration Centre AC will Sent to the electricity service provider SP.

[0131] S6.3: Decryption

[0132] S6.3.1: After receiving the data sent by the arbitration center AC, the power service provider SP checks the validity of the data by checking whether the following equation holds:

[0133]

[0134] S6.3.2: If the data is valid, the electricity service provider (SP) calculates: In getting Then, using the pollard lambda method, the power service provider SP can obtain Then, using the decoding function, the power service provider SP can obtain the user bill for a billing cycle and charge the user according to the bill.

[0135] S7: If a dispute arises regarding electricity charges, it will be handled through arbitration.

[0136] When user u ij When a dispute arises between a user and the power service provider SP regarding electricity charges during a certain period of time, the user u ij You can initiate an arbitration request to the arbitration center AC, which mainly includes the following five steps:

[0137] S7.1: For the disputed electricity fee ciphertext, the arbitration center AC uses the private key x AC Pre-decrypt it to obtain the pre-decrypted ciphertext B ij′ :

[0138]

[0139] S7.2: The electricity service provider SP uses the private key x SP Calculated And generate a signature

[0140]

[0141] Here T SP is the current timestamp, used to defend against replay attacks, ID SP It is the identity of the electricity service provider SP, and Bil is the disputed electricity bill.

[0142] S7.3: The electricity service provider SP will (σ SP ,ID SP ,W,Bill,T SP ,pk SP ) is sent to the arbitration center AC.

[0143] S7.4: The Arbitration Centre AC checks the validity of the report by checking whether the following equation holds:

[0144] e(σ SP ,g)=e(H(ID SP ||W||Bill||T SP ),pk SP ).

[0145] S7.5: If the report is valid, the arbitration center AC calculates In getting Then, using the pollard lambda method, the arbitration center AC can obtain Then, by comparing user u ij The arbitration center AC can effectively conduct arbitration based on the bills sent by the electricity service provider SP.

[0146] In addition, if user u ij If you want to query the electricity bill for a period of time (for example, if you want to query the electricity bill from June 10 to June 20), you can send a query request to the electricity service provider SP. The electricity service provider SP can use the fog node FN i Get user u ij The aggregated ciphertext of the queried time period is decrypted with the help of the arbitration center AC and sent to user u ij .

[0147] In summary, the present invention has the following advantages:

[0148] (1) In order for the power service provider SP to analyze data more precisely and provide better services, each smart meter SM ij The generated electricity consumption data is all l-dimensional. The present invention uses the additive homomorphic variant of the ElGamal cryptographic system to encrypt the data, thereby preventing user privacy leakage. Before encryption, the present invention uses a coding function to process the l-dimensional data into one-dimensional data to reduce the complexity of encryption, effectively saving computing and communication overhead. i All smart meters SM in its coverage area s The reported data is collected in ciphertext form, and then the validity of this data is verified through batch verification. If the verification is successful, it is aggregated, which effectively saves computing costs.

[0149] (2) Support secure billing based on real-time prices, that is, in the constructed scheme, the power service provider SP can provide each user with an electricity bill based on prices that change over time, while also preventing user privacy from being leaked to other parties. Users can reasonably adjust their energy usage patterns based on dynamically changing electricity prices, thereby improving resource utilization.

[0150] (3) A trusted third party is introduced as an arbitration center. When a user questions the bill sent by the power service provider SP, he or she can initiate an arbitration request to the arbitration center AC, which will resolve the dispute.

[0151] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A smart grid real-time processing method with privacy protection, using a smart grid real-time processing system with privacy protection, the smart grid real-time processing system with privacy protection comprising a root key generation center RKG, a smart meter SM ij , fog node FN i , arbitration center AC and power service provider SP, the root key generation center RKG is responsible for generating system public parameters and registration of each entity, the smart meter SM ij Responsible for generating real-time electricity consumption data of users and sending the encrypted electricity consumption data to the corresponding fog node FN regularly i , the fog node FN i Responsible for verifying the validity of the ciphertext, and forwarding all valid ciphertexts to the arbitration center AC after aggregation. The arbitration center AC is responsible for pre-decryption and arbitration disputes. The power service provider SP is responsible for collecting the total power consumption of all users in the grid coverage area and charging in real time; characterized by: The following steps are involved: The root key generation center RKG generates the initial parameters of the system; The process of generating the initial system parameters by the root key generation center RKG includes the following steps: The root key generation center RKG generates a bilinear map e:G×G→G τ , where G,G τ are two multiplicative cyclic groups of order q, and g is a generator of G; The root key generation center RKG selects a secure cryptographic hash function H:{0,1} * →G; Each entity in the system registers and obtains a key; Smart MeterSM ij Encrypt the power consumption data and send it to the corresponding fog node FN i ; The fog node FN i Perform aggregate verification; The arbitration center AC checks the validity of the report and performs pre-decryption; Real-time electricity billing; If there is a dispute over electricity charges, it will be handled through arbitration; The arbitration process includes the following steps: Step 1: For the disputed electricity fee ciphertext (U ij ,V ij ), the arbitration center AC uses the private key x AC Pre-decrypt it to get the pre-decrypted ciphertext Step 2: The power service provider SP uses the private key x SP calculate And generate a signature Where T SP is the current timestamp, used to defend against replay attacks, ID SP is the identity of the power service provider SP, Bill is the disputed electricity bill, and || is a concatenation symbol; Step 3: The power service provider SP will (σ SP ,ID SP ,W,Bill,T SP ,pk SP ) sent to the arbitration center AC; Step 4: The arbitration center AC checks the validity of the report by checking whether the following equation holds: e(σ SP ,g)=e(H(ID SP ||W||Bill||T SP ),pk SP ); Step 5: If the report is valid, the arbitration center AC calculates In getting Then, using the pollardlambda method, the arbitration center AC can obtain Among them, p m The electricity price for the mth period is then compared between the bills sent by the user and the electricity service provider SP, and the arbitration center AC conducts arbitration effectively.

2. The real-time processing method of smart grid with privacy protection according to claim 1, characterized in that: The key includes a private key and a public key. The root key generation center RKG randomly selects a private key for each registered entity and calculates and generates a corresponding public key.

3. The real-time processing method of smart grid with privacy protection according to claim 1, characterized in that: In the fog node FN i During the aggregation verification process, after receiving the data sent by all smart meters in the coverage area, the fog node FN i First, the validity of all reports is checked by running a batch verification algorithm, and then all valid ciphertexts are aggregated and sent to the arbitration center AC.

4. The real-time processing method of smart grid with privacy protection according to claim 1, characterized in that: In the process of the arbitration center AC checking the validity of the report and performing pre-decryption, the arbitration center AC first checks the validity of all reports by running a batch verification algorithm, performs pre-decryption after passing the verification, and sends the decrypted results to the power service provider SP.

5. The real-time processing method of smart grid with privacy protection according to claim 1, characterized in that: The process of real-time electricity billing includes the following steps: Fog Node FN i Aggregate electricity fee ciphertext; The arbitration center AC pre-decrypts the fog node FN i Aggregated electricity fee ciphertext; The power service provider SP performs final decryption on the result obtained after pre-decryption by the arbitration center AC to obtain the user's electricity fee for a billing cycle.

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