A pre-paid sts standard production key security enhancement method and system

Abstract

The application is suitable for the field of information security and smart grid technology, and relates to a prepayment STS standard production key security enhancement method and system. A signature module is introduced in a traditional STS production system, and the production module and the prepayment meter function are enhanced. The signature module is deployed to complete system initialization, the production module and the meter generate temporary ECC key pairs respectively, the meter information is signed by the signature module and verified by the production module, then the two generate a unique temporary session key through an ECC key negotiation algorithm, replace the DITK to complete the encryption and decryption of the key switching TOKEN and the secure transmission of the DUTK, and finally the temporary key is cleaned up. The application realizes one meter one temporary session key, eliminates the DITK leakage risk, has forward security, and only needs to modify the production link process, is fully compatible with the existing power selling system and the in-operation meter, and effectively strengthens the key security system of the STS standard production link.

Description

Technical Field

[0001] This invention belongs to the field of information security and smart grid technology, and in particular relates to a method and system for enhancing the security of prepaid STS standard production keys. Background Technology

[0002] According to the IEC 62055-41 standard (STS, the international standard widely used in prepaid electricity meters), each electricity meter needs to be pre-loaded with a symmetric key managed by the meter manufacturer during production, namely the Decoder Initialization Transmission Key (DITK). Before the meter leaves the factory, the manufacturer generates a "key switching token" through the production module. This token is encrypted using the DITK and contains a device-unique key (DUTK) derived from the customer's electricity sales key. Upon receiving this token, the meter decrypts it using its own stored DITK to obtain the DUTK, which it then uses as its working key after leaving the factory. Thereafter, all tokens related to electricity sales are encrypted and protected using this DUTK.

[0003] The drawback of the aforementioned existing technology lies in the fact that the security of the DITK, which serves as the starting point of the entire key system, relies entirely on the manufacturer's internal management processes. After generation, the key must be stored as a file and transmitted between different departments and operators during multiple stages, including development, testing, and production. This transmission process introduces significant security risks: if the DITK is intentionally leaked by internal personnel or exposed due to external attacks, attackers can use it to deduce the DUTK of any meter. Specifically, attackers can achieve their goals through two methods: if they obtain a generated "key switching token," they can directly decrypt the leaked DITK to obtain the meter's DUTK. Even without intercepting the "key switching token," attackers can generate a "key switching token" for a specific meter and decrypt it using the DITK to obtain the DUTK, provided they obtain the production module loaded with the corresponding key parameters. Therefore, the transmissibility of the DITK is a fundamental security weakness of the existing STS standard in the production stage. If DITK is leaked, it will cause the collapse of all meter key systems based on it. Attackers can bypass the legitimate electricity sales system to make illegal recharges, causing significant economic losses to electricity suppliers and meter manufacturers.

[0004] Therefore, it is imperative to address the safety risks arising from the transfer of DITK in the production process under the existing international prepaid standard (STS, IEC 62055-41). Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for enhancing the security of prepaid STS standard production keys, thereby resolving the security risks arising from DITK transmission during the production process of the international prepaid standard (STS, IEC 62055-41) in the existing technology; in addition, this invention also provides a system for enhancing the security of prepaid STS standard production keys.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for enhancing the security of prepaid STS standard production keys, comprising the following steps:

[0008] S10. Deploy a controlled signature module, generate an asymmetric key pair in the signature module, including a private key Priv_S and a public key Pub_S, and securely pre-install the public key Pub_S into the production module;

[0009] S20. When performing the key switching operation, the production module temporarily generates a first elliptic curve cryptography ECC key pair internally, including a private key Priv_M and a public key Pub_M. The prepaid meter temporarily generates a second ECC key pair internally, including a private key Priv_T and a public key Pub_T.

[0010] S30. Export the public key Pub_T of the prepaid meter, and digitally sign the combination information of the meter number, Pub_T, and parameter TI using the private key Priv_S of the signature module. Send the combination information and signature to the production line, and store the signature operation record in the security log. If multiple signatures of different public keys corresponding to the same meter number are detected, it indicates an illegal operation. The TI value needs to be changed and the signature operation needs to be completed again.

[0011] S40. The production line sends the combined information, signature, and target customer's supply group code SGC to the production module. The production module verifies the signature validity using the public key Pub_S. If the verification is successful, the production module uses the private key Priv_M and the prepaid meter's Pub_T to calculate the shared secret value and derive a temporary session key using the ECC key negotiation algorithm. Then, it uses the session key to encrypt a key switching token containing the device's unique key DUTK (generated from parameters such as SGC and TI). If the verification fails, an error is returned.

[0012] S50. The encrypted key switching token and the public key Pub_M of the production module are sent to the prepaid meter. The prepaid meter uses the private key Priv_T and Pub_M to calculate the same session key using the same ECC key negotiation algorithm. Then, the key switching token is decrypted using the session key to obtain the DUTK and stored securely.

[0013] S60. After the prepaid meter completes the key switch, it erases the second ECC key pair and the session key for this session; the production module discards the session key for this session after the interaction is completed.

[0014] Furthermore, in step S10, the public key Pub_S is pre-installed in the production module by binding it to the key loading file KLF, in order to ensure the authenticity of the pre-installed public key.

[0015] Furthermore, in step S30, the signature operation record includes at least operator ID, table number, Pub_T, TI, and timestamp to enable traceability of the signature operation.

[0016] Furthermore, in S40, the ECC key negotiation algorithm is the Elliptic Curve Diffie-Hellman Key Exchange Protocol.

[0017] Furthermore, in S60, the first ECC key pair of the production module is erased uniformly after the key switching operation of a batch of prepaid meters is completed.

[0018] Furthermore, when calculating the shared secret value to derive the session key, the key derivation is performed by combining the identity identifiers of the production module and the prepaid meter, and one or more random numbers.

[0019] Secondly, the present invention also provides a prepaid STS standard production key security enhancement system, comprising:

[0020] The Key Management Center (KMC) is used to issue and supply key loading files (KLF) related to the SGC for production modules.

[0021] The enhanced production module has a built-in signature module whose public key Pub_S is used for signature verification. It can temporarily generate ECC key pairs and negotiate a session key with the public key of the prepaid meter through the ECC key negotiation algorithm. The session key is then used to encrypt the DUTK to generate a key switching token.

[0022] The enhanced prepaid meter can temporarily generate ECC key pairs and negotiate the same session key with the public key of the production module through the ECC key negotiation algorithm. The session key is used to decrypt the key switching token to obtain the DUTK. After the key switching is completed, the temporary key and session key can be automatically erased.

[0023] The signature module is an independent hardware security module used to generate asymmetric key pairs and can digitally sign the combined information of the prepaid meter number, Pub_T, and TI using the private key Priv_S, while recording the signature operation log.

[0024] Furthermore, the signature module is a USB hardware dongle, a smart card, or a software module running on a specific security server, and its internal private key Priv_S is securely stored and cannot be exported.

[0025] Furthermore, the ECC key generation and key negotiation functions of the enhanced prepaid meter are integrated into the meter's main control security chip, or implemented by an external dedicated security encryption chip.

[0026] Furthermore, the ECC key negotiation algorithm in the system can be replaced with RSA or other asymmetric cryptographic algorithms that support key negotiation.

[0027] The prepaid STS standard production key security enhancement method and system provided by this invention have at least the following advantages compared with the prior art:

[0028] Existing international prepaid standards (STS, IEC 62055-41) pose security risks during the production process due to DITK transmission. This invention fundamentally eliminates the risk of leakage that may arise from the transmission and storage of DITKs during production, achieving a unique temporary session key per meter, significantly enhancing security during the production phase. Even if data from a single production interaction is compromised, the uniqueness and post-use destruction of the temporary key pair prevent attackers from cracking the keys of other meters. This invention only modifies relevant functions within the plant, having no impact on the large-scale, deployed electricity sales system and operating meters, resulting in low upgrade costs and high feasibility. This invention employs an asymmetric cryptographic system to enhance the security of symmetric key distribution, representing current mainstream cryptographic practices and demonstrating mature and reliable technology. Attached Figure Description

[0029] To more clearly illustrate the solution of the present invention, a brief introduction will be given to the drawings used in the description of the embodiments below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 A flowchart illustrating a method for enhancing the security of prepaid STS standard production keys, provided as an embodiment of the present invention;

[0031] Figure 2 This is an architecture diagram of a prepaid STS standard production key security enhancement system provided for an embodiment of the present invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0034] This invention provides a method for enhancing the security of prepaid STS standard production keys, applied to the production process of the international prepaid standard (STS, IEC 62055-41). The method includes the following steps:

[0035] S10. Deploy a controlled signature module, generate an asymmetric key pair in the signature module, including a private key Priv_S and a public key Pub_S, and securely pre-install the public key Pub_S into the production module; S20. When performing a key switching operation, the production module internally temporarily generates a first elliptic curve cryptography ECC key pair, including a private key Priv_M and a public key Pub_M, and the prepaid meter internally temporarily generates a second ECC key pair, including a private key Priv_T and a public key Pub_T; S30. Export the public key Pub_T of the prepaid meter. Digitally sign the combination of the meter number, Pub_T, and parameter TI using the private key Priv_S of the signature module. Send the combination information and signature to the production line, and simultaneously store the signature operation record in the security log. If multiple signatures for the same meter number corresponding to different public keys are detected, it indicates an illegal operation; the TI value must be changed and the signature operation re-completed. S40. The production line sends the combination information, signature, and the target customer's supply group code SGC to the production module. The production module verifies the signature validity using the public key Pub_S. After successful verification, the production module uses the private key Priv_M and the prepaid meter's Pub_T to calculate the shared secret using the ECC key negotiation algorithm. The system calculates and derives a temporary session key, then encrypts a key switching token containing the device's unique key DUTK (generated from parameters such as SGC and TI) using the session key; if verification fails, an error is returned; S50, the encrypted key switching token and the production module's public key Pub_M are sent to the prepaid meter. The prepaid meter uses its private key Priv_T and Pub_M to calculate the same session key using the same ECC key negotiation algorithm, then decrypts the key switching token using the session key to obtain the DUTK and stores it securely; S60, after the prepaid meter completes the key switching, it erases the second ECC key pair and the session key for this session; the production module discards the session key for this session after the interaction is completed.

[0036] This invention implements a one-table-one-temporary-session-key system, eliminating the risk of DITK leakage, providing forward security, and requiring only modifications to the production process. It is fully compatible with existing electricity sales systems and in-operation meters, and allows for flexible replacement of cryptographic algorithms and adjustment of functional implementation. The technology is mature, upgrades and modifications are low-cost, and it effectively strengthens the key security system of the STS standard production process.

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0038] This invention provides a method for enhancing the security of prepaid STS standard production keys, applied to the production process of the international prepaid standard (STS, IEC 62055-41), combined with... Figures 1 to 2In this embodiment, the method for enhancing the security of prepaid STS standard production keys includes the following steps:

[0039] S10. System Initialization: Deploy a controlled signature module, which generates an asymmetric key pair, including a private key Priv_S and a public key Pub_S. The private key Priv_S is securely stored and cannot be exported. The public key Pub_S is securely pre-installed in the production module, and its authenticity can be ensured by binding it with KLF, etc.

[0040] In this embodiment, the signature module can be a standalone USB hardware dongle, a smart card, or a software module running on a specific security server, as long as it can securely store the signature private key and complete the signature operation.

[0041] S20. Temporary key pair generation: When performing a key switching operation, the production module internally generates a first elliptic curve cryptography (ECC) key pair, including a private key Priv_M and a public key Pub_M. The prepaid meter internally generates a second ECC key pair, including a private key Priv_T and a public key Pub_T. Priv_M and Priv_T are protected against external reading, while Pub_M and Pub_T are exportable.

[0042] S30. Signature of meter information (meter number + Pub_T + TI): The operator of the signature module securely exports the public key Pub_T of the prepaid meter, and digitally signs the combination of meter number, Pub_T, and parameter TI using the private key Priv_S of the signature module. The combination information and signature are sent to the production line, and the signature operation record is stored in the security log. If multiple signatures with different public keys corresponding to the same meter number are detected, it indicates an illegal operation. The TI value must be changed and the signature operation must be completed again.

[0043] Specifically, in this embodiment, all signature operations (operator ID, table number, Pub_T, TI, timestamp) are recorded in the security log to ensure traceability. If a table number is found to have been signed multiple times with different public keys (or the same table number is restricted to being signed only once; if duplicate signatures are detected, an alarm will be triggered), it indicates that a fraudulent public key has been used. The value of TI needs to be changed, and (table number + Pub_T + new TI) needs to be re-signed. The new TI is then used to regenerate the key for switching the token, preventing DUTK leakage.

[0044] S40. Session Key Negotiation and TOKEN Generation: The production line sends the combined information, signature, and target customer's supply group code SGC to the production module. The production module verifies the signature validity using the public key Pub_S. If the verification is successful, the production module uses the private key Priv_M and the prepaid meter's Pub_T to calculate the shared secret value and derive a temporary session key using the ECC key negotiation algorithm. Then, it encrypts the key switching TOKEN containing the device's unique key DUTK (generated from parameters such as SGC and TI) using the session key. If the verification fails, an error is returned.

[0045] Specifically, in this embodiment, this Session Key functionally replaces the original DITK. Subsequently, the production module uses this Session Key to encrypt the DUTK generated by parameters such as SGC and TI, forming a key switching token.

[0046] In this embodiment, the ECC key negotiation algorithm is the Elliptic Curve Diffie-Hellman key exchange protocol; in other embodiments, the ECC key negotiation algorithm may also be replaced by other asymmetric cryptographic algorithms that support key negotiation, such as RSA based on the large number factorization problem (although its efficiency is usually lower than ECC) or other elliptic curve algorithm variants.

[0047] S50. Send the encrypted key switching token and the production module's public key Pub_M (exported first) to the prepaid meter. The prepaid meter uses the private key Priv_T and Pub_M to calculate the same session key using the same ECC key negotiation algorithm. Then, it decrypts the key switching token using the session key to obtain the DUTK and stores it securely.

[0048] S60. After the prepaid meter completes the key switch, the second ECC key pair and the session key of this session are immediately and securely erased. The production module discards the session key of this session after the interaction is completed. The key pair can be erased with a delay (e.g., after a batch of meters is completed, to improve efficiency).

[0049] Furthermore, in this embodiment, after negotiating the shared secret, in addition to directly deriving it as a session key, more complex key derivation (KDF) can be performed by combining the identity identifiers of both parties, random numbers, etc., to enhance the independence and binding of the key.

[0050] Furthermore, in this embodiment, the prepaid STS standard production key security enhancement method can be integrated into the main control security chip of the meter, or the generation and negotiation of the temporary key can be completed by an external, dedicated security encryption chip.

[0051] This invention also provides a prepaid STS standard production key security enhancement system, comprising:

[0052] The Key Management Center (KMC) is used to issue and supply key loading files (KLF) related to the SGC for the production module. The enhanced production module has a built-in signature module whose public key, Pub_S, is used for signature verification. It can temporarily generate ECC key pairs and negotiate a session key with the public key of the prepaid meter using the ECC key negotiation algorithm. The session key is used to encrypt the DUTK and generate a key switching token. The enhanced prepaid meter can temporarily generate ECC key pairs and negotiate the same session key with the production module's public key using the ECC key negotiation algorithm. The session key is used to decrypt the key switching token to obtain the DUTK. After key switching, the temporary key and session key can be automatically erased. The signature module is an independent hardware security module used to generate asymmetric key pairs and can digitally sign the meter number, Pub_T, and TI combination information of the prepaid meter using the private key Priv_S, while simultaneously recording the signature operation log.

[0053] Furthermore, in this embodiment, the signature module is a USB hardware dongle, a smart card, or a software module running on a specific security server, and its internal private key Priv_S is securely stored and cannot be exported.

[0054] Furthermore, in this embodiment, the ECC key generation and key negotiation functions of the enhanced prepaid meter are integrated into the meter's main control security chip, or implemented by an external dedicated security encryption chip.

[0055] Furthermore, in this embodiment, the ECC key negotiation algorithm in the system can be replaced with RSA or other asymmetric cryptographic algorithms that support key negotiation.

[0056] The prepaid STS standard production key security enhancement method and system described in the above embodiments, compared with the prior art, addresses the security risks arising from DITK transmission in the production process of the existing international prepaid standard (STS, IEC 62055-41). This invention fundamentally eliminates the leakage risks that may arise from the transmission and storage of DITK during the production process, achieving one temporary session key per meter, greatly improving security during the production stage. Even if the data from a single production interaction is compromised, the uniqueness of the temporary key pair and its post-use destruction prevent attackers from cracking the keys of other meters. This invention only modifies the relevant functions of the plant's production, having no impact on the large-scale, deployed electricity sales system and operating meters, resulting in low upgrade costs and high feasibility. This invention employs an asymmetric cryptographic system to enhance the security of symmetric key distribution, which is the mainstream practice in current cryptographic applications and is technically mature and reliable.

[0057] Obviously, the embodiments described above are merely preferred embodiments of the present invention, and not all embodiments. The accompanying drawings illustrate preferred embodiments of the present invention, but do not limit the scope of the patent. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this invention.

Claims

1. A method for enhancing the security of prepaid STS standard production keys, characterized in that, Includes the following steps: S10. Deploy a controlled signature module, generate an asymmetric key pair in the signature module, including a private key Priv_S and a public key Pub_S, and securely pre-install the public key Pub_S into the production module; S20. When performing the key switching operation, the production module temporarily generates a first elliptic curve cryptography ECC key pair internally, including a private key Priv_M and a public key Pub_M. The prepaid meter temporarily generates a second ECC key pair internally, including a private key Priv_T and a public key Pub_T. S30. Export the public key Pub_T of the prepaid meter, and digitally sign the combination information of the meter number, Pub_T, and parameter TI using the private key Priv_S of the signature module. Send the combination information and signature to the production line, and store the signature operation record in the security log. If multiple signatures of different public keys corresponding to the same meter number are detected, change the TI value and re-complete the signature operation. S40. The production line sends the combined information, signature, and target customer's supply group code SGC to the production module. The production module verifies the signature validity using the public key Pub_S. If the verification is successful, the production module uses the private key Priv_M and the prepaid meter's Pub_T to calculate the shared secret value and derive a temporary session key using the ECC key negotiation algorithm. Then, it uses the session key to encrypt the key switching token containing the device's unique key DUTK. If the verification fails, an error is returned. S50. The encrypted key switching token and the public key Pub_M of the production module are sent to the prepaid meter. The prepaid meter uses the private key Priv_T and Pub_M to calculate the same session key using the same ECC key negotiation algorithm. Then, the key switching token is decrypted using the session key to obtain the DUTK and stored securely. S60. After the prepaid meter completes the key switch, erase the second ECC key pair and the session key for this session. The production module discards the session key for this session after the interaction is complete.

2. The method for enhancing the security of prepaid STS standard production keys according to claim 1, characterized in that, In step S10, the public key Pub_S is pre-installed in the production module by binding it to the key loading file KLF to ensure the authenticity of the pre-installed public key.

3. The method for enhancing the security of prepaid STS standard production keys according to claim 1, characterized in that, In step S30, the signature operation record includes at least operator ID, table number, Pub_T, TI, and timestamp to enable traceability of the signature operation.

4. The method for enhancing the security of prepaid STS standard production keys according to claim 1, characterized in that, In S40, the ECC key negotiation algorithm is the Elliptic Curve Diffie-Hellman Key Exchange Protocol.

5. A method for enhancing the security of prepaid STS standard production keys according to claim 1, characterized in that, In S60, the first ECC key pair of the production module is erased uniformly after the key switching operation of a batch of prepaid meters is completed.

6. A method for enhancing the security of prepaid STS standard production keys according to claim 1, characterized in that, When calculating the shared secret value to derive the session key, the key is derived by combining the identity identifiers of the production module and the prepaid meter, and one or more random numbers.

7. A system employing the method as described in any one of claims 1 to 6, characterized in that, include: The Key Management Center (KMC) is used to issue and supply key loading files (KLF) related to the SGC for production modules. The enhanced production module has a built-in signature module whose public key Pub_S is used for signature verification. It can temporarily generate ECC key pairs and negotiate a session key with the public key of the prepaid meter through the ECC key negotiation algorithm. The session key is then used to encrypt the DUTK to generate a key switching token. The enhanced prepaid meter can temporarily generate ECC key pairs and negotiate the same session key with the public key of the production module through the ECC key negotiation algorithm. The session key is used to decrypt the key switching token to obtain the DUTK. After the key switching is completed, the temporary key and session key can be automatically erased. The signature module is an independent hardware security module used to generate asymmetric key pairs and can digitally sign the combined information of the prepaid meter number, Pub_T, and TI using the private key Priv_S, while recording the signature operation log.

8. The system according to claim 7, characterized in that, The signature module is a USB hardware dongle, a smart card, or a software module running on a specific security server, and its internal private key Priv_S is securely stored and cannot be exported.

9. The system according to claim 7, characterized in that, The enhanced prepaid meter's ECC key generation and key negotiation functions are integrated into the meter's main control security chip, or implemented by an external dedicated security encryption chip.

10. The system according to claim 7, characterized in that, The ECC key negotiation algorithm in the system can be replaced with RSA or other asymmetric cryptographic algorithms that support key negotiation.

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