Alliance chain identity privacy protection method and system based on multilevel group signature and distributed key management

Abstract

The invention relates to an alliance chain identity privacy protection method and system based on multi-level group signature and distributed key management, and belongs to the field of block chain technology, network and information security. According to the method, a multi-level group signature structure is adopted, anonymous identity verification is achieved in the transaction process, privacy protection is further enhanced through zero-knowledge proof, anonymous identity verification is achieved in the transaction process, it is ensured that privacy of participants is not leaked, a homomorphic encryption algorithm is used in the signature and verification process of transaction data, and the transaction data are subjected to identity authentication. And privacy leakage is prevented. And meanwhile, the Shamir secret sharing algorithm divides the master key and stores the master key in a plurality of sub-group members in a distributed manner, so that the anti-attack capability and the key security are enhanced. According to the method, a dynamic group member management and double signature verification mechanism is further introduced, so that the flexibility and the overall security are improved. The method has significant advantages in the aspects of identity anonymity, data integrity and efficiency, and is suitable for alliance chain application scenarios with high privacy and security requirements.

Description

Technical Field

[0001] The present invention belongs to the fields of blockchain technology, network and information security, and relates to a method and system for identity privacy protection of consortium blockchain based on multi-level group signature and distributed key management. Background Art

[0002] With the rapid development and wide application of blockchain technology, the consortium blockchain, as a blockchain form between public blockchains and private blockchains, has gradually become an ideal choice for data sharing and collaboration among enterprises due to its unique permission management and privacy control characteristics. Through preset access mechanisms and consensus rules, the consortium blockchain can establish an efficient and secure data exchange platform among multiple mutually trusted entities, showing great application potential in fields such as finance, supply chain, and healthcare.

[0003] However, in actual application scenarios, the identity privacy protection and system security of the consortium blockchain still face severe challenges. First, in terms of identity privacy protection, existing solutions mainly use technologies such as group signature and ring signature to achieve identity anonymity. Although these methods can hide the specific identity of the transaction initiator, there are still the following problems: (1) The group administrator, as a trusted third party, holds the complete identity information of group members and is prone to being a single point of failure and an attack target; (2) The group signature scheme requires updating the group key when members join and revoke, resulting in a large computational overhead; (3) Existing solutions are difficult to cope with complex attack scenarios such as Sybil Attack and Collusion Attack.

[0004] Second, in terms of key management, although traditional secret sharing technology can disperse key risks, there are still the following deficiencies: (1) The process of share distribution and reconstruction in the threshold scheme is prone to exposing key information; (2) The protection of the group private key is insufficient and cannot effectively resist attacks from internal malicious nodes; (3) There is a lack of a dynamic adjustment mechanism and it is difficult to adapt to scenarios where consortium blockchain members change frequently.

[0005] In addition, with the development of quantum computing technology, traditional cryptographic algorithms based on discrete logarithm and large integer factorization face potential security threats. Most existing privacy protection solutions do not consider the requirements of post-quantum cryptography and it is difficult to ensure the long-term security of the consortium blockchain system.

[0006] Therefore, the consortium blockchain urgently needs a more effective method for identity privacy protection. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method and system for identity privacy protection in consortium blockchains based on multi-level group signatures and distributed key management, which can enhance security and anonymity while ensuring high efficiency.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] Solution 1:

[0010] A system for identity privacy protection in consortium blockchains based on multi-level group signatures and distributed key management. By introducing multi-level group signature technology, it realizes double identity anonymous authentication during the transaction process, and adopts the Shamir secret sharing algorithm for distributed management of the master key to enhance the overall security and anti-attack ability. Additionally, zero-knowledge proof and homomorphic encryption algorithms are introduced to further enhance privacy protection and security during the identity authentication and data processing processes.

[0011] The system includes a group signature module, a distributed key management module, a transaction signature module, a transaction verification module, a zero-knowledge proof module, and a dynamic member management module.

[0012] The group signature module uses elliptic curve cryptography and zero-knowledge proof technology to achieve identity anonymous authentication during the transaction process and the non-forgeability of signatures.

[0013] The distributed key management module uses the Shamir secret sharing algorithm to split the master key into multiple key fragments and distribute them to multiple subgroup members.

[0014] The signature module generates multi-level transaction signatures, combining the group signature algorithm and the homomorphic encryption algorithm to ensure the non-forgeability of signatures and the privacy of data.

[0015] The zero-knowledge proof module is used to verify the validity of signatures without revealing specific identity information.

[0016] The verification module sequentially verifies the outer signature and the inner signature to ensure the legality and anonymity of the transaction.

[0017] The dynamic member management module is used to handle the joining and leaving of group members and dynamically adjust the distribution of key fragments.

[0018] Furthermore, the distributed key management module realizes the secure splitting and storage of the master key through the Shamir secret sharing algorithm, avoiding the threats of single-point failures and malicious nodes, and ensuring the security of key recovery by setting a threshold t.

[0019] Furthermore, the multi-level group signature generated by the signature module includes an outer-layer signature generated by the main group members and an inner-layer signature generated by the subgroup members, and requires double verification, further enhancing the security and privacy protection level of transactions.

[0020] Furthermore, during the verification process, the verification module integrates a homomorphic encryption algorithm to decrypt the encrypted transaction data and perform a hash comparison to ensure that the data has not been tampered with during transmission and processing, and uses the characteristics of homomorphic encryption to complete partial verification operations in the ciphertext state, further enhancing data privacy.

[0021] Solution 2: A method for identity privacy protection in consortium blockchain based on multi-level group signature and distributed key management, specifically including: initialization phase, member joining or leaving phase, signature construction phase, signature verification phase, and consortium blockchain recording phase.

[0022] Initialization phase: The system administrator is responsible for setting relevant parameters, generating public and private key pairs for the main group and subgroup, as well as functions required by the system, and securely storing the public keys in the consortium blockchain; the administrator uses the distributed key management method, i.e., the Shamir secret sharing algorithm, to split the master key into multiple key fragments and distribute them to multiple subgroup members. The master key can only be restored with the cooperation of at least t members, avoiding the threats of single point of failure and malicious nodes.

[0023] Member joining or leaving phase: Adopt a dynamic member management method to support the dynamic joining and leaving of group members; when a member joins, the system administrator generates new key fragments and re-distributes the keys to ensure that the new member can participate in the signature process without affecting the key security of existing members; when a member leaves, the system automatically adjusts the distribution of key fragments and revokes the key access rights of the departing member to prevent potential threats to the system.

[0024] Signature construction phase: Adopt a multi-level signature structure to generate a multi-level group signature. Specifically, combine the group signature algorithm and the homomorphic encryption algorithm to construct a double-signature mechanism. The multi-level group signature includes an outer-layer signature generated by the main group members and an inner-layer signature generated by the subgroup members, and requires double verification, further enhancing the security and privacy protection level of transactions.

[0025] Signature verification phase: The verification node uses the homomorphic encryption algorithm combined with the zero-knowledge proof technology to verify the outer-layer signature and the inner-layer signature in turn to confirm the legality and authenticity of the hierarchical group signature generated by the transaction user.

[0026] Consortium blockchain recording phase: Verify the node signature through hash comparison, and record the successfully verified transactions on the blockchain.

[0027] Furthermore, in the signature construction phase, when generating group signatures, elliptic curve cryptography and zero-knowledge proof technology are adopted to achieve identity anonymous authentication and signature non-forgery during the transaction process.

[0028] The beneficial effects of the present invention are as follows:

[0029] First, through the multi-level group signature mechanism, the identity anonymity and signature non-forgery during the transaction process are significantly improved, ensuring the privacy protection of both parties in the transaction.

[0030] Second, by adopting distributed key management and using the Shamir secret sharing algorithm to split the master key, the security of the master key is enhanced, avoiding the threats of single-point failure and malicious nodes.

[0031] Third, combined with the elliptic curve cryptography algorithm, an efficient and secure encryption and signature algorithm is provided, ensuring the performance and security requirements of the system in a high-concurrency environment.

[0032] Fourth, the multi-level signature structure further improves the overall security and anti-attack ability of the system through a double verification mechanism, and is applicable to the consortium chain application scenarios with high requirements for privacy and security.

[0033] Fifth, the dynamic member management module ensures the flexibility and security of the system, can dynamically respond to changes in group members, and maintain the continuous and secure operation of the system.

[0034] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0036] Figure 1 is a model diagram of the consortium chain identity privacy protection system provided by an embodiment of the present invention;

[0037] Figure 2 is a flowchart of the post-secret sharing process in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following describes the implementation manners of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0039] Please refer to Figures 1 to 2 , the present invention provides a consortium chain identity privacy protection method based on multi-level group signature and distributed key management. By introducing the multi-level group signature technology, double identity anonymous authentication in the transaction process is realized, and the Shamir secret sharing algorithm is used for distributed management of the master key to enhance the overall security and anti-attack ability. The zero-knowledge proof and homomorphic encryption algorithms are introduced to further enhance the privacy protection and security in the identity authentication and data processing processes. This method mainly involves the following technical methods:

[0040] Multi-level group signature: By introducing the multi-level group signature technology, anonymous authentication of identities is realized in the transaction verification process, ensuring that the identity information of both parties in the transaction is not leaked, while ensuring the authenticity and legality of the transaction.

[0041] Distributed key management: The Shamir secret sharing algorithm is used to split the master key into multiple key fragments and distribute them to multiple subgroup members. The master key can only be recovered with the cooperation of at least t members, avoiding the threats of single-point failures and malicious nodes.

[0042] Multi-level signature structure: Combining group signature and distributed key management, a double-signature mechanism is constructed. The outer signature is generated by the main group members, and the inner signature is generated by the subgroup members. Double verification is required to further improve the security of the system.

[0043] Homomorphic encryption: The homomorphic encryption algorithm is applied in the transaction signature and verification module to encrypt the transaction data, ensuring that the data remains encrypted during the signature and verification processes to prevent data leakage.

[0044] Zero-knowledge proof integration: The zero-knowledge proof technology is introduced into the group signature module, allowing the verification node to verify the validity of the signature without obtaining any specific identity information, further improving the privacy protection level of identity authentication.

[0045] Elliptic Curve Cryptography: Utilize elliptic curve cryptography to provide efficient and secure encryption and signature algorithms, ensuring performance and security requirements in a high-concurrency environment. The specific implementation includes the selection of elliptic curves, the determination of generators, the generation of key pairs, and the design of signature verification algorithms to ensure the overall performance and security of the system.

[0046] Dynamic Member Management: Introduce a dynamic member management module to support the dynamic joining and leaving of group members. When a member joins, the system administrator generates a new key fragment and reallocates the keys to ensure that the new member can participate in the signature process without affecting the key security of existing members. When a member leaves, the system automatically adjusts the key fragment allocation, revoking the key access rights of the departing member to prevent potential threats to the system. Dynamically adjust the key allocation strategy to ensure high levels of security and flexibility even when members change.

[0047] As Figure 1 shown, an embodiment of the present invention provides a method for protecting the identity privacy of a consortium chain based on multi-level group signature and distributed key management. Its architecture consists of multiple key entities, each entity undertaking specific functions to ensure security. The method mainly includes the following core entities:

[0048] 1) Verification Nodes

[0049] Verification nodes are responsible for performing the legality verification of transactions, the authenticity verification of signatures, and the data integrity check, and record the verified transactions on the consortium chain. They are the core part of the method.

[0050] 2) Primary Group Members

[0051] Primary group members consist of all members. Their main responsibilities include generating outer-layer signatures to ensure the legality of transactions and the non-forgery of signatures. When the primary key needs to be recovered, the primary group members also undertake the task of collaborative recovery to ensure the security and integrity of the primary key through collective cooperation. This mechanism of multi-member participation effectively prevents threats to the security of the primary key caused by the failure or malicious attack of a single node.

[0052] 3) System Administrator

[0053] The system administrator is responsible for the management and maintenance of the entire system. Their responsibilities cover the initialization settings of the system, the generation and management of key pairs, handling the dynamic joining and leaving of members, and the allocation and maintenance of Shamir secret sharing parameters.

[0054] 4) Consortium Chain

[0055] As a distributed ledger, the consortium chain is responsible for storing all transaction records, which are jointly maintained by distributed nodes, avoiding the risk of single-point failure, and ensuring data consistency and integrity through a consensus mechanism.

[0056] 5) Subgroup members

[0057] Subgroup members are responsible for generating inner-layer signatures, managing their own key pairs, and participating in the sharding and custody of the main group private key.

[0058] The workflow of this method is divided into five main stages: initialization stage, member joining or leaving stage, signature construction stage, signature verification stage, and consortium chain recording stage. The following will describe the specific steps and operations of each stage in detail:

[0059] 1) Initialization stage

[0060] In the initialization stage, the system administrator is responsible for setting relevant parameters, generating the public and private key pairs of the main group and subgroup, and system required functions, and securely storing the public keys in the consortium chain. To enhance security, the administrator uses the Shamir secret sharing algorithm to split the main group private key into n shares, ensuring that at least t shares (0 < t < n) are necessary for reconstructing the private key.

[0061] The steps are as follows:

[0062] (1) First, select a large prime number q as the modulus of the finite field F P , and then construct the elliptic curve E: y 2 = x 3 + ax + b, where the curve parameters a, b ∈ F P , and a and b satisfy the specific non-zero condition 6a + 28b ≠ 0 (mod p). Subsequently, select a generator G on the curve, whose order l is a large prime number and satisfies a length exceeding 160 bits to ensure the security of elliptic curve cryptography, that is, there exist two points Q 1 and Q 2 on the elliptic curve, and there exists such that Q 1 = cQ 2 , and in cryptography, it is feasible to calculate Q c from 2 and Q 1 , but not vice versa. Let the group size be n, the threshold for recovering the secret be set to t (t < n), and select two auxiliary subgroups H 1 and H 2 , where a hash function is used here to ensure that data can be mapped to a predetermined number field to improve security: H 1 : H 2 :

[0063] Subsequently, the public and private key pairs of the main group are generated. The system administrator generates the generator g of the main group through a pseudo-random number generation algorithm, thereby obtaining the private key of the main group and calculating the corresponding public key. This pair of public and private keys is used in the signature and verification processes of the main group members.

[0064] g = h p-1 / q mod p, {h ∈ 1, 2,..., n}, 1 < h < p - 1

[0065] K m = g x mod p

[0066] (2) For each subgroup member, the system administrator generates its private key and calculates the corresponding public key K s . These public and private key pairs are used for the operations of subgroup members in signature and key management, ensuring that each member has an independent and secure key pair. The calculation formula is as follows:

[0067] K s = g y mod p

[0068] (3) To improve the security of the main group's private key, the Shamir secret sharing algorithm is used here to split the secret into r (r = 1, 2, 3..., n) key fragments, corresponding to r holders U of the 1 , U 2 ,..., U r of the secret fragments, and a recovery threshold t (t < n) is set. Each subgroup member holds one of the key fragments, ensuring that the main key can be recovered only when at least t members cooperate. This distributed key management mechanism effectively prevents single-point failures and malicious attacks:

[0069] Step 1: Select et (et > n - 1) non-zero coefficients {a lm |a lm ∈ GF(p); 1 ≤ l ≤ e, 0 ≤ m ≤ t - 1; a lm ≠ 0} to construct k (t - 1)-order polynomials:

[0070] Step 2: Calculate the secret fragments corresponding to the secret sharing participants, that is, distribute the secret fragments:

[0071]

[0072] Step 3: According to the characteristics of the Shamir secret sharing algorithm, ensure that the secret s satisfies s ∈ Z q , and within the predefined number field, there exist appropriate integers d l and w l(l = 1, 2, 3..., e) such that:

[0073]

[0074] After completing the above operations, the private key k of the main group m will be split into r parts, and a set of at least t parts is required to successfully reconstruct the secret. Next, these secret fragments are distributed through a secure communication channel, and the main group private key is assigned to each verification node, f l (x r ) will then be transmitted to the corresponding participants, and the relevant parameters w l , d l , a, b, G, p will also be broadcast, and f(x) will be securely stored.

[0075] (4) The system administrator is responsible for returning the public-private key pairs (K m , k m ) of the main group and the subgroup, and providing the relevant parameters required for Shamir secret sharing, as follows:

[0076] K m = (p, q, g, K m , shares), K s = (r, g, K s ),

[0077] Shamir = (n, t, shares)

[0078] The private key shards of the main group are generated through the Shamir secret sharing algorithm. In the secret recovery phase (i.e., recovering the private key of the main group), the operation steps are as follows: Suppose there are g (e ≤ g ≤ n) participants {U 1 , U 2 ,..., U n} responsible for recovering the secret s i , and each participant needs to calculate and provide their own Lagrange factor, and finally reconstruct the secret through set operations.

[0079]

[0080] 2) Member Join or Exit Phase

[0081] In this phase, when a new member (numbered i) officially joins the group, the following steps need to be completed to verify their identity and maintain system integrity:

[0082] (1) The new member first generates a pair of public-private key pairs (K i , k i ) for the basis of identity authentication.

[0083] (2) The new member submits their complete public key K i to the administrator to apply for joining the group.

[0084] (3) After the administrator verifies the identity of the new member and passes the verification, the public key K of the new member is publicly announced i and recorded on the consortium blockchain, and at the same time, the member identity information ID = {ID 1 , ID 2 ,... ID n} is updated.

[0085] 3) Signature construction phase

[0086] In this phase, the signature subject constructs a hierarchical digital group signature in detail. The specific steps are as follows:

[0087] (1) Random number selection

[0088] The signer needs to randomly select an integer r ∈ [1, q - 1] as the random number used in the signature process.

[0089] (2) Recover the master group private key

[0090] During the secret recovery process, participant U i sends a recovery request to the collective {U 1 , U 2 ,..., U r} and uses the r - 1 Lagrange factors received to calculate the original secret. This mechanism ensures that even if an attacker has some of the Lagrange factors, they cannot restore a valid secret. The specific operation process is as follows:

[0091] Step 1: Participant U i calculates its corresponding Lagrange factor according to the received secret share f l (x r ). The calculation process is as follows: The calculation process is as follows:

[0092] Step 2: After receiving the recovery request, participant U i sends the Lagrange factor to the other r - 1 participants through a secure channel.

[0093] Step 3: Use the r - 1 Lagrange factors collected to calculate and recover the secret:

[0094] (3) Calculation of the outer - layer signature

[0095] After obtaining the master group private key, the master group members use the private key km Generate the first-layer signature. The specific steps include: ① Randomly select Calculate ② Calculate the hash value h i = H(m, ID i ); ③ Use the homomorphic encryption algorithm to calculate the first-layer signature:

[0096]

[0097] Among them, In the formula, g is the generator of the main group, and p, q represent the order of the main group.

[0098] (4) Construct the inner-layer signature

[0099] The signer performs a hash process on the data m to be signed by executing the hash function H, thereby obtaining the hash value: h 1 = H(m, ID), and the subgroup members combine their own private key k i with the obtained hash value h 1 to generate the inner-layer signature: σ 2 = r + k i *h 1 mod p.

[0100] At the same time, in combination with the zero-knowledge proof module, the subgroup members generate a zero-knowledge proof to prove that they have the qualification of a valid group signature without revealing specific identity information. This process further ensures the legality of the signature and the anonymity of the member identity.

[0101] (5) Sign to the requester

[0102] The signer returns the constructed double-layer signature T = (σ 1 , σ 2 , h 1 ) to the requester, where σ 1 and σ 2 represent the outer-layer and inner-layer signatures respectively, and h 1 is the data to be signed after hash processing, and the signed data has been hash processed.

[0103] 4) Signature verification stage

[0104] In the signature verification stage, the verification node needs to confirm the legality and authenticity of the hierarchical group signature generated by the trading user. This process requires using the public and private keys of the main group, the components of the hierarchical group signature (such as the random number r , the hash value h 1 ', and h' 2 ), and the relevant verification parameter T'. The specific verification steps are as follows:

[0105] (1) Calculate the corresponding hash value for the received data d and member identifier ID:

[0106] h 1 ' = H 1 '(d, ID), h' 2 = H' 2 (d, r)

[0107] (2) Use the generator to calculate the verification parameter for authenticity verification:

[0108]

[0109] (3) If T' == T and the calculation result meets the predetermined conditions, the signature is considered valid; otherwise, the transaction is determined to be invalid.

[0110] 5) Consortium blockchain recording stage

[0111] In the final recording stage, to ensure the integrity and authenticity of the transaction, the verification node needs to execute a series of verification steps to confirm that the transaction in the consortium blockchain has not been tampered with and has valid identity authentication. Only the successfully verified transactions can be recorded on the blockchain. At the same time, the key pairs of the main group and sub - groups also need to be maintained. The specific verification process includes the following steps:

[0112] 1) Recalculate the hash value by performing a hash operation on the transaction data d, the user identifier ID of the transaction participant, and the random number to confirm that the data has not been tampered with:

[0113] h 3 = H 3 (d), h 4 = H 4 (ID), h 5 = H 3 (r)

[0114] 2) According to the above calculation results, recalculate the parameters required for signature verification to ensure its correctness:

[0115] (1) Calculate h 1 ' = H 1 '(d, ID), h' 2 = H' 2 (d, r);

[0116] (2) Calculate

[0117] 3) Verify the fragments of the main group private key to ensure the accuracy and integrity of each private key fragment:

[0118]

[0119] 4) Recalculate the signature parameters based on the restored key and verification parameters for verification:

[0120] (1) Calculate the hash value: h 3 = H 3 (d);

[0121] (2) Calculate the verification parameters:

[0122] 5) Perform signature verification: If T' == T", it proves that the signature is valid and the transaction will be recorded on the chain; if they are inconsistent, it is considered a verification failure.

[0123] The above has introduced in detail a method for protecting the identity privacy of a consortium chain based on multi-level group signature and distributed key management. Combining the units and algorithm steps of each example described in the embodiments disclosed in this article, it can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical method. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A consortium chain identity privacy protection system based on multi-level group signature and distributed key management, characterized in that: The system includes a group signature module, a distributed key management module, a transaction signature module, a transaction verification module, a zero-knowledge proof module and a dynamic member management module; The group signature module adopts elliptic curve cryptography and zero-knowledge proof technology to achieve anonymous identity verification and unforgeability of signatures during transactions; The distributed key management module uses the Shamir secret sharing algorithm to divide the master key into multiple key fragments and distribute them to multiple sub-group members; The signature module generates multi-level transaction signatures, combining the group signature algorithm and the homomorphic encryption algorithm to ensure the unforgeability of the signature and the privacy of the data; The zero-knowledge proof module is used to verify the validity of the signature without revealing specific identity information; The verification module verifies the outer signature and the inner signature in turn to ensure the legitimacy and anonymity of the transaction; The dynamic member management module is used to process the joining and leaving of group members and dynamically adjust the distribution of key fragments.

2. The alliance chain identity privacy protection system according to claim 1 is characterized in that: The distributed key management module implements the secure segmentation and storage of the master key through the Shamir secret sharing algorithm, avoids the threat of single point failure and malicious nodes, and ensures the security of key recovery by setting a threshold t.

3. The alliance chain identity privacy protection system according to claim 1 is characterized in that: The multi-level group signature generated by the signature module includes an outer signature generated by main group members and an inner signature generated by sub-group members, and needs to be double-verified.

4. The alliance chain identity privacy protection system according to claim 1 is characterized in that: The verification module integrates a homomorphic encryption algorithm during the verification process, decrypts and hashes the encrypted transaction data to ensure that the data has not been tampered with during transmission and processing, and uses the characteristics of homomorphic encryption to complete some verification operations in the ciphertext state.

5. A consortium chain identity privacy protection method based on multi-level group signature and distributed key management, characterized in that: The method specifically includes: Initialization phase: Set relevant parameters, generate the public and private key pairs of the main group and sub-groups and the functions required by the system, and store the public key securely in the alliance chain; use the distributed key management method, namely the Shamir secret sharing algorithm, to split the master key into multiple key fragments and distribute them to multiple sub-group members. The master key can only be recovered with the cooperation of at least t members; Member joining or leaving stage: Dynamic member management methods are used to support dynamic joining and leaving of group members; when a member joins, the system administrator generates new key fragments and reallocates keys; when a member leaves, the system automatically adjusts the distribution of key fragments and revokes the key access rights of the departing member; Signature construction stage: A multi-level group signature is generated using a multi-level signature structure. Specifically, a double signature mechanism is constructed by combining the group signature algorithm and the homomorphic encryption algorithm. The multi-level group signature includes an outer signature generated by the main group members and an inner signature generated by the sub-group members, which needs to be double-verified; Signature verification stage: The verification node uses homomorphic encryption algorithm combined with zero-knowledge proof technology to verify the outer signature and inner signature in turn, confirming the legitimacy and authenticity of the hierarchical group signature generated by the transaction user; Consortium chain recording stage: The node signature is verified through hash comparison, and the successfully verified transactions are recorded on the blockchain.

6. The alliance chain identity privacy protection method according to claim 1 is characterized in that: In the signature construction stage, elliptic curve cryptography and zero-knowledge proof technology are used to generate the group signature to achieve anonymous identity verification and unforgeability of the signature during the transaction process.

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