CN118018211A - Trusted distributed digital identity authentication method and system - Google Patents

Abstract

The present invention belongs to the field of blockchain technology, and specifically relates to a trusted distributed digital identity authentication method and system. The present invention utilizes a centralized oracle to obtain off-chain data, and the credential center performs signature confirmation, generates pre-credentials, and determines the attributes and statements of the credential. Zero-knowledge proofs are generated for the credential through RLWE, and the credential center records and makes it public, so that the service recipient has the master credential. Credentials are managed through update/revocation requests, and credential abuse can be limited and credential thieves or attackers can be locked out through public information, thereby achieving effective digital identity authentication and ensuring the security and reliability of the digital identity authentication system.

Description

A trusted distributed digital identity authentication method and system

Technical Field

The present invention belongs to the technical field of blockchain, and in particular relates to a trusted distributed digital identity authentication method and system.

Background technique

Decentralized Digital Identity (DID) is a digital identity system based on blockchain technology. DID's verifiable credentials are an important technology in the current field of digital identity management. It can ensure that identity data is authentic and reliable, while also protecting the privacy of identity users and ensuring that data related to personal identity belongs to the individual.

The current decentralized digital identity credentials are generally sourced from the user himself, third-party institutions, and historical data on the chain. The generation, verification, update, and revocation of verifiable credentials are generally achieved using digital signatures, zero-knowledge proofs, or symmetric and asymmetric encryption technologies.

The acquisition of verifiable credential content from the user himself is prone to low information authenticity, low trustworthiness, and data falsification; data from third-party institutions can easily lead to bloated interactions with different third-party institutions on the chain, lack of efficiency, and face data duplication and data processing problems; the credential content comes from historical data on the chain, which will increase the burden of the blockchain and reduce scalability. In addition, the above three acquisition methods all face the problem of user privacy leakage and user data lag. With the development of quantum computing, cryptographic algorithms such as digital signatures, zero-knowledge proofs, and asymmetric encryption used in the current existing verifiable credential management mechanism are threatened. Quantum computers can theoretically crack many existing encryption algorithms, and with the development of technology, the original cryptographic algorithms will be under greater threat and the possibility of being cracked will increase.

Summary of the invention

Based on the problems existing in the prior art, the present invention provides a trusted distributed digital identity authentication method and system to solve the security problems in the traditional data identity authentication system.

In a first aspect of the present invention, the present invention provides a trusted distributed digital identity authentication method, the method comprising:

The oracle obtains off-chain information from the service recipient and sends the off-chain information to the credential center;

The credential center confirms the authenticity of the off-chain information and signs the off-chain information, generates a pre-credential based on the off-chain information and the off-chain information signature, and sends the pre-credential to the service recipient;

The service recipient generates the parameters required for zero-knowledge proof of the master credential based on ring-band error learning according to the pre-credential, encrypts the required parameters and generates a ciphertext to send to the credential center;

The credential center decrypts the ciphertext, verifies the signature and calculates the required parameters. If the verification is successful, a master credential is issued to the service recipient based on the required parameters. At the same time, the master credential is formed into a credential list, and the public parameters are formed into a public list and saved in the database. If the verification fails, the required parameters are discarded.

The service recipient generates a zero-knowledge proof related to the master credential based on the issued master credential, and sends the zero-knowledge proof related to the master credential to the service provider;

The service provider verifies the received zero-knowledge proof of the master credential with the parameters accessed in the database to determine whether they are consistent. If they are consistent, the service provider provides services to the service recipient. If they are inconsistent, the service provider refuses to provide services to the service recipient.

In a second aspect of the present invention, the present invention further provides a trusted distributed digital identity authentication system, the system comprising:

A service recipient, the service recipient having a decentralized identity, for storing its own pre-credentials and generating zero-knowledge proof-related parameters of the master credential based on the pre-credentials;

An oracle, which is used to obtain off-chain information of the service recipient;

The credential center is used to confirm the authenticity of the off-chain information and sign the off-chain information, generate a pre-credential based on the off-chain information and the off-chain information signature, and send the pre-credential to the service recipient. It is also used to decrypt the ciphertext, calculate the required parameters after verifying the signature, and if the verification is successful, issue a master credential to the service recipient based on the required parameters, and save the master credential into a credential list and public parameters in the database. If the verification fails, the required parameters are discarded;

A database, wherein the database is used to store a credential list and a public list;

The service provider verifies whether the user's pre-credentials are consistent with the corresponding values in the public information list, and provides services if they are consistent, and refuses services if they are inconsistent.

Beneficial effects of the present invention:

Compared with the traditional way of obtaining credential data, the technology of the present invention uses a decentralized oracle to obtain the off-chain information of the service recipient and the signature of the credential center, thereby ensuring the authenticity, validity, and real-time nature of the credential source, improving the efficiency of information interaction between the blockchain and third-party institutions, and reducing the burden on the blockchain. In the process of credential verification, generation, update, and revocation, a zero-knowledge proof based on lattice cryptography is adopted to ensure the privacy security of users. At the same time, due to the use of lattice cryptography, the quantum resistance of zero-knowledge proof is enhanced, and it can resist quantum attacks. Even if the attacker knows the public key, he cannot successfully calculate the private key within polynomial time, and theoretically cannot be cracked successfully. At the same time, due to the existence of a credential list and public information, if an attacker uses an old credential to try to pass verification after the credential is updated, he will be marked as a suspicious attacker.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a trusted distributed digital identity authentication system according to an embodiment of the present invention;

FIG2 is a schematic diagram of the structure of a trusted distributed digital identity authentication system according to a preferred embodiment of the present invention;

FIG3 is a flow chart of a trusted distributed digital identity authentication method according to an embodiment of the present invention;

FIG4 is a flow chart of a trusted distributed digital identity authentication method according to a preferred embodiment of the present invention.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

FIG1 is a schematic diagram of a trusted distributed digital identity authentication system according to an embodiment of the present invention. As shown in FIG1 , the system includes a service receiver, a service provider, an oracle, a credential center, and a database; wherein:

The service receiver has an off-chain identity, which is a decentralized identity. The off-chain information is obtained through the off-chain identity of the service receiver. The oracle is used to obtain the off-chain information of the service receiver from the off-chain identity of the service receiver. The credential center is used to confirm the authenticity of the off-chain information and sign the off-chain information. A pre-credential is generated based on the off-chain information and the off-chain information signature, and the pre-credential is sent to the service receiver. The service receiver generates the required parameters for the zero-knowledge proof of the master credential based on loop-band error learning (RLWE) according to the pre-credential, encrypts the required parameters and generates a ciphertext to send to the credential center. The credential center issues the master credential to the service receiver based on the parameters, and at the same time forms a credential list with the master credential and saves the public parameters in the public list in the database. The service provider determines whether to provide services to the service receiver by verifying whether the zero-knowledge proof of the master credential sent by the service receiver is equal to the public parameters stored in the database, so as to achieve secure digital identity authentication.

FIG2 is a schematic diagram of a trusted distributed digital identity authentication system according to a preferred embodiment of the present invention. As shown in FIG2 , the system still includes a service receiver, a service provider, an oracle, a credential center and a database; wherein:

The service receiver has an off-chain identity, which is a decentralized identity. The off-chain information is obtained through the off-chain identity of the service receiver; the oracle is used to obtain the off-chain information of the service receiver from the off-chain identity of the service receiver; the credential center is used to confirm the authenticity of the off-chain information and sign the off-chain information; a pre-credential is generated according to the off-chain information and the off-chain information signature, and the pre-credential is sent to the service receiver; the service receiver generates the required parameters for the zero-knowledge proof of the master credential based on loop error learning (RLWE) according to the pre-credential, and encrypts the required parameters to generate a ciphertext and sends it to the credential center. Different from the above embodiment, the required parameters for the zero-knowledge proof of the master credential based on loop error learning (RLWE) here are the required parameters that can be used for update/revocation; the credential center issues the master credential to the service receiver according to the parameters, and updates the credential list at the same time, and saves the public list update to the database; the service provider verifies whether the zero-knowledge proof of the master credential sent by the service receiver is equal to the public parameters stored in the database, thereby determining whether to provide services to the service receiver to achieve secure digital identity authentication.

FIG3 is a flow chart of a trusted distributed digital identity authentication method according to an embodiment of the present invention. As shown in FIG3 , the method includes:

101. The oracle obtains off-chain information from the service recipient and sends the off-chain information to the credential center;

In an embodiment of the present invention, the service recipient indicates its identity through the DID identifier, and the oracle can obtain the corresponding off-chain information from the service recipient, including the credential attribute name A, the credential claim value V, the information provider Pd, etc.

In the embodiment of the present invention, the oracle is a decentralized oracle, which can obtain data from a designated off-chain data source, i.e., the off-chain identity of the service receiver, verify the obtained off-chain data, and perform subsequent operations such as uploading the data after the verified consensus. These data can be some sensitive data, such as financial data of banks, tax data of enterprises, identity data of governments, etc.

102. The credential center confirms the authenticity of the off-chain information and signs the off-chain information, generates a pre-credential based on the off-chain information and the off-chain information signature, and sends the pre-credential to the service recipient;

In an embodiment of the present invention, the credential center signs the off-chain information, and the off-chain information itself and the off-chain information signature constitute a pre-credential, and the pre-credential is expressed as PC = {DIDs, A, V, Pd, σ}, DIDs is the decentralized identity of the service recipient s, and the decentralized identity is a new type of identifier with global uniqueness, high reliability resolvability and cryptographic verifiability. A is the credential attribute name, V is the credential claim value, Pd is the service provider, which can be used to distinguish different service providers, and σ is the off-chain information signature.

103. The service recipient generates the required parameters for zero-knowledge proof of the master credential based on ring-band error learning according to the pre-credential, encrypts the required parameters and generates a ciphertext to send to the credential center;

In an embodiment of the present invention, the service recipient generates the required parameters for zero-knowledge proof of the master credential based on ring-band error learning according to the pre-credential, and encrypts the required parameters to generate ciphertext and sends it to the credential center, including:

The service receiver generates a random matrix based on the modulus q, the degree n of the polynomial, and the noise parameter α that conforms to the discrete Gaussian distribution. Error distribution e = χ _α ;

The modulus q may be a prime number greater than 8.

According to the random matrix M and the knowledge public key P _k , the knowledge private key S _k =M×P _k +2e is generated;

The knowledge public key is the public key involved in the zero-knowledge proof, and the present invention does not make any specific limitation on this.

Generate the service receiver public key P _u =M×S _u +2e according to the random matrix M and the service receiver private key S _u ;

Generate the certificate center public key P _c =M×S _c +2e according to the random matrix M and the certificate center private key S _c ;

Generate the verification feature value based on the service receiver's private key _Su , the knowledge private key _Sk and the certificate center's public key _Pc

Among them, the superscript T represents transposition, and char is the indicator function, which is expressed as:

Among them, _E1 represents the first range, _E2 represents the second range, and they are respectively expressed as:

In this embodiment, by judging Whether the value of is within the first range or the second range, the corresponding verification feature value ω can be determined.

Generate the knowledge verification value through hash function _H1 and modulo 2 operation Mod ₂ And the indicator value used to update/revoke the characteristic value/>

Among them, H ₁ represents the hash function, Mod ₂ represents the modulo 2 operation, which can be written as:

Generate the ciphertext C=E _MC (P _u ,P _k ,K,ω,ν,σ) according to the off-chain information signature and the above parameters;

Among them, E _MC is the encryption function.

104. The credential center decrypts the ciphertext, verifies the signature and calculates the required parameters. If the verification is successful, the primary credential is issued to the service recipient according to the required parameters, and the primary credential is formed into a credential list, and the public parameters are formed into a public list and saved in a database. If the verification fails, the required parameters are discarded.

In the embodiment of the present invention, the credential center decrypts the ciphertext and verifies the signature, including if the knowledge verification value W is equal to the knowledge verified value K, then calculating the credential public verification value J = H ₂ (W), the request and revocation request verification value The main certificate is issued to the service recipient, and the main certificate MC = (DIDs, _Pu , _Pk , Ι, W) is formed into a certificate list, and the public parameter _PVu = ( _Pu , J, DIDs) is formed into a public list and saved in the database; if the knowledge verification value W is not equal to the knowledge verified value K, the knowledge verification value is discarded;

Among them, _Pk is the knowledge public key, _Sc is the credential center private key, ν is the indication value used to update/revoke the characteristic value, _Pu is the service receiver public key, DIDs is the decentralized identity of the service receiver s, _H2 is the hash function, and Mod ₂ is the modulo 2 operation.

In the embodiment of the present invention, after receiving the ciphertext, the certificate center first decrypts the ciphertext, verifies the signature σ, and calculates the corresponding parameter knowledge verification value and knowledge is verified value Whether to calculate the credential disclosure verification value J and the request and revocation request verification value Ι is determined by verifying whether the knowledge verification value and the knowledge verified value are equal.

It can be understood that hash function _H1 and hash function _H2 can be the same type of hash function or different types of hash functions. In this embodiment, hash function _H1 and hash function _H2 are different types of hash functions. _H1 can be SHA256, and hash function _H2 can be RIPEMD160.

105. The service recipient generates a zero-knowledge proof related to the master credential based on the issued master credential, and sends the zero-knowledge proof related to the master credential to the service provider;

In the embodiment of the present invention, the service recipient generates a zero-knowledge proof related to the master credential based on the master credential issued by the credential center, which is expressed as Proof _MC =(P _u ,H ₂ (K)).

Wherein, _Pu represents the public key of the service recipient, and K represents the knowledge verified value.

106. The service provider verifies the received zero-knowledge proof of the master credential with the parameters accessed in the database to determine whether they are consistent. If they are consistent, the service provider provides services to the service recipient. If they are inconsistent, the service provider refuses to provide services to the service recipient.

In the embodiment of the present invention, the service provider performs verification based on the received zero-knowledge proof related to the master credential and the parameters accessed from the database, including the service provider obtaining the zero-knowledge proof Proof _MC = ( _Pu , _H2 (K)) related to the master credential from the data recipient, and based on the public parameter _PVu , verifying whether _H2 (K) is equal to J. If they are equal, the credential passes, otherwise it fails.

Among them, K represents the knowledge verified value, _Pu is the public key of the service receiver, and J represents the credential public verification value.

FIG4 is a flow chart of a trusted distributed digital identity authentication method according to a preferred embodiment of the present invention. As shown in FIG4 , the method includes:

201. The oracle obtains off-chain information from the service recipient and sends the off-chain information to the credential center;

202. The credential center confirms the authenticity of the off-chain information and signs the off-chain information, generates a pre-credential based on the off-chain information and the off-chain information signature, and sends the pre-credential to the service recipient;

203. The service recipient generates the required parameters for zero-knowledge proof of the master credential based on ring-band error learning according to the pre-credential, encrypts the required parameters and generates a ciphertext to send to the credential center;

204. The credential center decrypts the ciphertext, verifies the signature and calculates the required parameters. If the verification is successful, the primary credential is issued to the service recipient according to the required parameters, and the primary credential is formed into a credential list, and the public parameters are formed into a public list and saved in a database. If the verification fails, the required parameters are discarded.

205. The service recipient generates a zero-knowledge proof related to the master credential based on the issued master credential, and sends the zero-knowledge proof related to the master credential to the service provider;

206. The service provider verifies the received zero-knowledge proof of the master credential with the parameters accessed in the database to determine whether they are consistent. If they are consistent, the service provider provides services to the service recipient. If they are inconsistent, the service provider refuses to provide services to the service recipient.

207. The service receiver sends a ciphertext of the credential update/revoke request and the request parameters. After receiving the ciphertext, the credential center decrypts it, calculates whether the parameters are the same as the saved related parameters, and decides whether to update/revoke. If updated/revoke, the credential list is updated and the corresponding public parameters are changed.

In the embodiment of the present invention, the service receiving party sends an update/revocation request to the credential center to generate a new knowledge public key P _k ′, knowledge private key S _k ′=M×P _k ′+2e;

Calculates the verified value for the update request

Calculate new indicator value for updating/revoking characteristic value

If it is a request to update the credentials, generate a new verification feature value

The knowledge verification value generated by the hash function and modulo 2 operation Generate ciphertext _Cu = _EMC ( _Pu , _Pk ', ω', I', ν');

After receiving the update request and the ciphertext, the certificate center decrypts it and decides whether to update by verifying whether I′=I:

If they are equal, no update is needed; if they are not equal, an update is needed;

If updated, calculate New parameter knowledge verification value The new credential public verification value J ₁ =H ₂ (W′), then the original (DIDs, _Pu , P _k , Ι, W) in the credential list is updated to (DIDs, _Pu , P _k ′, I ₁ , W′), and the public parameter PV _u =(P _u , J, J ₁ , DIDs); where J represents the credential public verification value, where J can be considered as a former name in personal information, and can be used in subsequent processes to find the operations used by the credential before the update.

If it is a revocation request, the user sends the ciphertext _Cu = _EMC ( _Pu , _Pk ', I');

After receiving the update request and ciphertext, the credential center decrypts it and decides whether to revoke it by verifying whether I′=I holds. If the verification is successful, the original (DIDs, _Pu , _Pk , Ι, W) in the credential list is deleted and the public parameter _PVu =( _Pu , NULL, DIDs) is updated. NULL indicates that the credential public verification value is null.

The present invention uses a centralized oracle to obtain off-chain data, and the credential center performs signature confirmation, generates pre-credentials, and determines the attributes and statements of the credential. Zero-knowledge proofs are generated for the credential through RLWE, and the credential center records and makes it public, so that users have master credentials. Credentials are managed through update/revoke requests, and credential abuse can be limited and credential thieves or attackers can be locked out through public information, thereby achieving effective digital identity authentication and ensuring the security and reliability of the digital identity authentication system.

A person skilled in the art may understand that all or part of the steps in the various methods of the above embodiments may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which may include: ROM, RAM, disk or CD, etc.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. A method of trusted distributed digital identity authentication, the method comprising:

the prophetic machine obtains the information under the chain from the service receiver, and send the information under the chain to the credential center;

The certificate center confirms the authenticity of the information under the chain, signs the information under the chain, generates a pre-certificate according to the information under the chain and the information under the chain, and sends the pre-certificate to a service receiver;

the service receiver generates a main certificate related zero knowledge proof required parameter based on ring belt error learning according to the pre-certificate, encrypts the required parameter, generates a ciphertext and sends the ciphertext to a certificate center;

The credential center decrypts the ciphertext, calculates required parameters after verifying the signature, issues a master credential to a service receiver according to the required parameters if the verification is passed, forms a credential list from the master credential, stores a public list formed by the public parameters in a database, and discards the required parameters if the verification is not passed;

The service receiver generates a master certificate related zero knowledge proof according to the issued master certificate, and sends the master certificate related zero knowledge proof to the service provider;

And the service provider verifies the received related zero knowledge proof of the master certificate and the parameters accessed in the database to judge whether the data are consistent, if so, the service provider provides the service for the service receiver, and if not, the service provider refuses to provide the service for the service receiver.

2. The method of claim 1, wherein the pre-credential is represented as pc= { DIDs, a, V, pd, σ }, DIDs being the de-centralized identity of the service receiver s, a being the credential attribute name, V being the credential declaration value, pd being the service provider, σ being the out-of-chain information signature.

3. The method of claim 1, wherein the service receiver generates parameters required by the zero knowledge proof of the main certificate based on the ring belt error learning according to the pre-certificate, encrypts the parameters required to generate ciphertext and sends the ciphertext to the certificate center, and the method comprises the service receiver generating a random matrix according to a modulus q, a degree n of a polynomial, a noise parameter alpha conforming to the discrete Gaussian distribution, and the likeError distribution e=χ _α; generating a knowledge private key S _k＝M×P_k +2e according to the random matrix M and the knowledge public key P _k; generating a service receiver public key P _u＝M×S_u +2e according to the random matrix M and the service receiver private key S _u; generating a credential center public key P _c＝M×S_c +2e according to the random matrix M and the credential center private key S _c; generating verification feature values according to the service receiver private key S _u, the knowledge private key S _k and the certificate center public key P _c Knowledge verified value is generated through Hash function H ₁ and modulo two operation Mod ₂ Indication value/>, for updating/revoking feature valuesAnd generating a ciphertext C=E _MC(P_u,P_k,K,ω,ν,σ),E_MC as an encryption function and char as an indication function according to the information signature under the chain and the parameters.

4. The method of claim 1, wherein the step of verifying the signature by decrypting the ciphertext by the credential center includes calculating a credential disclosure verification value j=h ₂ (W) and a request and revocation request verification value if the knowledge verification value W is equal to the knowledge verified value KIssuing a master certificate to a service receiver, forming a certificate list by the master certificate MC= (DIDs, P _u,P_k, I, W), forming a public list by public parameters PV _u＝(P_u, J, DIDs, and storing the public list into a database; if the knowledge verification value W is not equal to the knowledge verified value K, discarding the knowledge verification value; wherein, P _k is a public key of knowledge, S _c is a private key of a credential center, v is an indication value for updating/revoking a feature value, P _u is a public key of a service receiver, DIDs is a decentralised identity of the service receiver S, H ₂ is a hash function, and Mod ₂ is a modulo two operation.

5. The method of claim 1, wherein the service provider verifying the received primary credential related zero knowledge Proof against the parameters accessed in the database comprises the service provider obtaining the primary credential related zero knowledge Proof of _MC＝(P_u,H₂ (K) in the data receiver, verifying whether H ₂ (K) is equal to J based on the public parameter PV _u, if equal, the credentials pass, and if unequal, the credentials do not pass, wherein H ₂ is a hash function, K represents a knowledge verified value, P _u is a service receiver public key, and J represents a credential public verification value.

6. The method of claim 1, further comprising the steps of sending a ciphertext of the credential update/revocation request and the request parameter by the service receiver, decrypting the ciphertext after the credential center receives the ciphertext, calculating whether the parameter is the same as the stored related parameter, determining whether to update/revoke, and if so, updating the credential list and changing the corresponding public parameter.

7. The method of claim 6, wherein the service receiver sends an update/revocation request to the credential center, generates a new public knowledge key P _k ', a private knowledge key S _k′＝M×P_k' +2e, and calculates the verified value of the update requestCalculating new indication value for updating/revoking feature valueIf the certificate request is updated, a new verification feature value/> isgeneratedKnowledge verified value/>, generated by a hash function and a modulo two operationGenerating ciphertext C _u＝E_MC(P_u,P_k ', omega ', I ', v '), decrypting after the credential center receives the update request and the ciphertext, determining whether to update by verifying whether I ' =I is true, and if so, calculating/>New parameter knowledge verification valueA new certificate public verification value J ₁＝H₂ (W '), the original (DIDs, P _u,P_k, I, W) in the certificate list is updated to be (DIDs, P _u,P_k′,I₁, W'), and the public parameters PV _u＝(P_u,J,J₁, DIDs are updated; if the revocation request user sends ciphertext C _u＝E_MC(P_u,P_k ', I '), the credential center decrypts after receiving the update request and the ciphertext, determines whether to revoke by verifying whether I ' =i is true, if so, deletes the original (DIDs, P _u,P_k, I, W) in the credential list, and updates the public parameters PV _u＝(P_u, NULL, DIDs.

8. A trusted distributed digital identity authentication system, the system comprising:

The service receiver is provided with a decentralization identity and is used for storing a pre-credential of the service receiver and generating zero knowledge proof related parameters of a main credential according to the pre-credential;

The pre-prediction machine is used for acquiring the information under the chain of the service receiver;

The certificate center is used for confirming the authenticity of the information under the chain and signing the information under the chain, generating a pre-certificate according to the information under the chain and the signature of the information under the chain, sending the pre-certificate to a service receiver, decrypting the ciphertext, calculating required parameters after verifying the signature, issuing a main certificate to the service receiver according to the required parameters if the verification is passed, and simultaneously storing a certificate list and public parameters formed by the main certificate into a database, and discarding the required parameters if the verification is not passed;

The database is used for storing a certificate list and a public list;

And the service provider is used for verifying whether the pre-credentials of the user are consistent with the corresponding values in the public information list, if so, providing the service, and if not, rejecting the service.

9. The system of claim 8, wherein the service receiver is further configured to send a ciphertext of the credential update/revocation request and the request parameter, decrypt the ciphertext after the credential center receives the ciphertext, calculate whether the parameter is the same as the stored related parameter, determine whether to update/revoke, and update the credential list and change the corresponding public parameter if so.