Anonymous Double Offline Transaction Method and System Based on ID Cryptography and Trusted Intermediary

Abstract

The present invention discloses an anonymous dual-offline transaction method and system based on ID cryptography and a trusted intermediary. The method includes the following steps: S1, issuing keys based on ID cryptography for the payer and the payee through a key management server; S2, using a communication method to achieve short-range communication between the trusted intermediary and the payer and the payee; S3, completing a dual-offline transaction between the payer and the payee in an offline state through the trusted intermediary; S4, using commercial banks and central banks to confirm the transaction in an online state. Beneficial effects: Through the use of ID cryptography and a trusted intermediary, the anonymous dual-offline transaction of digital currency can be better realized. Compared with the prior art, the present invention can better protect the privacy information of users and make transactions (especially dual-offline transactions) more secure.

Description

Technical Field

[0001] The present invention relates to the field of information technology, and particularly to an anonymous double-offline transaction method and system based on ID cryptography and a trusted intermediary. Background Art

[0002] Currently, with the rapid development of the times, the method of digital currency payment is favored by more and more people. As a substitute for cash banknotes at the digital level, digital currency payment tools (DC / EP, Digital Currency and Electronic Payment) are of great significance for building a cashless society.

[0003] Patent No. CN201911053809 discloses an anonymous transaction method and system based on digital currency. Although it effectively solves the problem that the identity of the payee is easily locked by the payer, however, this patent can only conduct online transactions, making the subsequent transaction process of the user's temporary identity only possible when it is recognized by its own server. When the user cannot communicate with its own server, the payee of this method cannot use the user's temporary identity to verify its digital signature for the transaction (in the digital signature based on digital certificates, since the user needs to hide the real identity, it cannot provide a digital certificate containing its real identity and cannot prove the association between its temporary identity and its digital certificate, so it cannot use its digital certificate to verify its digital signature for the transaction; in the digital signature based on ID cryptography, since the user needs to hide the real identity, it cannot provide its real identity and cannot prove the association between its temporary identity and its real identity, so it cannot use its real identity to verify its digital signature for the transaction). Therefore, the payee cannot recognize the legality of this transaction and complete the entire transaction process without receiving any identity credentials from the payer. That is, the problem of this patent method is that it cannot conduct double-offline transactions (double-offline transactions are transactions where both the payer and the payee are offline). Summary of the Invention

[0004] Aiming at the problems in the related technologies, the present invention provides an anonymous double-offline transaction method and system based on ID cryptography and a trusted intermediary to overcome the above technical problems existing in the existing related technologies.

[0005] For this reason, the specific technical solutions adopted by the present invention are as follows:

[0006] According to one aspect of the present invention, there is provided an anonymous double-offline transaction method based on ID cryptography and a trusted intermediary, and the method includes the following steps:

[0007] S1. Pre-preparation stage: The key management server issues keys based on ID cryptography to the payer and the payee.

[0008] S2. Preparation stage: Implement short - range communication between the trusted intermediary and the payer and payee using a communication method;

[0009] S3. Double - offline transaction stage: Complete the double - offline transaction between the payer and payee in an offline state through the trusted intermediary;

[0010] S4. Online transaction stage: Use commercial banks and the central bank to confirm the transaction in an online state;

[0011] Among them, when the key management server issues the system public and private keys to the payer / payee, a random number is taken as the system private key, the corresponding system public key is calculated based on this system private key, and the system private key is saved at the key management server;

[0012] When the key management server issues public and private keys to the payer / payee, a random number is taken as the true identity ID of the payer / payee, the corresponding public key is calculated based on this true identity ID, and the corresponding private key is calculated based on this public key.

[0013] Further, the implementation of short - range communication between the trusted intermediary and the payer and payee using a communication method in S2 includes the following steps:

[0014] S21. Implement short - range communication between the trusted intermediary and the payer using a communication method;

[0015] S22. Implement short - range communication between the trusted intermediary and the payee using a communication method.

[0016] Further, the implementation of short - range communication between the trusted intermediary and the payer using a communication method in S21 specifically includes the following steps:

[0017] S211. The trusted intermediary generates a first combined message and sends it to the payer;

[0018] S212. The payer receives the first combined message, obtains the identity ID of the trusted intermediary, and verifies whether it is the same as the true identity IDM of the trusted intermediary; at the same time, the payer verifies the first timestamp and the first signature. If the verification fails, the transaction fails; if the verification is successful, the payer recognizes the trusted intermediary as the owner of the true identity IDM of the trusted intermediary;

[0019] S213. The payer generates its own anonymous identity IDA and a second combined message, and sends the second combined message to the trusted intermediary;

[0020] S214. The trusted intermediary receives the second combined message and decrypts the true identity IDA of the payer TRUE, verify the second timestamp and the second signature. If the verification fails, the transaction fails. If the verification is successful, the remitter is recognized as the real identity IDA of the remitter. TRUE owner.

[0021] Furthermore, the use of a communication method in S22 to achieve short-range communication between the trusted intermediary and the payee specifically includes the following steps:

[0022] S221. The trusted intermediary generates a third combined message and sends it to the payee.

[0023] S222. The payee receives the third combined message, obtains the identity ID of the trusted intermediary, and verifies whether it is the same as the real identity IDM of the trusted intermediary. At the same time, the payee verifies the third timestamp and the third signature. If the verification fails, the transaction fails. If the verification is successful, the trusted intermediary is recognized as the owner of the real identity IDM of the trusted intermediary.

[0024] S223. The payee generates its own anonymous identity IDB and a fourth combined message, and sends the fourth combined message to the trusted intermediary.

[0025] S224. The trusted intermediary receives the fourth combined message and decrypts the real identity IDB of the payee TRUE , verifies the fourth timestamp and the fourth signature. If the verification fails, the transaction fails. If the verification is successful, the payee is recognized as the owner of the real identity IDB of the payee. TRUE owner.

[0026] Furthermore, the trusted intermediary completes the double-offline transaction between the remitter and the payee in an offline state in S3, including the following steps:

[0027] S31. The trusted intermediary generates a fifth combined message and sends it to the remitter.

[0028] S32. The remitter receives the fifth combined message for verification. If the verification is successful, the remitter generates a first sending message and sends it to the trusted intermediary.

[0029] S33. The trusted intermediary receives the first sending message and verifies it. If the verification is successful, the trusted intermediary generates a second sending message and sends it to the payee.

[0030] S34. The payee receives the second sending message and verifies it. If the verification is successful, the payee generates a new fourth combined message and stores it.

[0031] Furthermore, the remitter receiving the fifth combined message for verification in S32 and generating a first sending message and sending it to the trusted intermediary if the verification is successful specifically includes the following steps:

[0032] The remitter receives the fifth combined message and verifies the fifth timestamp and the fifth signature. If the verification fails, the transaction fails. If the verification is successful, the user with the payee's anonymous identity IDB is recognized as the payee. At the same time, the remitter sends the first sending message with the transaction time, the remitter's anonymous identity IDA, the payee's anonymous identity IDB, and the digital currency to the trusted intermediary.

[0033] Further, in S33, the trusted intermediary receives the first sending message and verifies it. If the verification is successful, generating the second sending message and sending it to the payee specifically includes the following steps:

[0034] The trusted intermediary receives the first sending message and verifies it. If the verification fails, the transaction fails. If the verification is successful, a new second combined message is generated, and the new second combined message is encrypted using the public key of the remitter's corresponding remitter commercial bank to obtain an encrypted message and sent to the remitter commercial bank. At the same time, the trusted intermediary generates the second sending message and sends it to the payee.

[0035] Further, in S34, the payee receives the second sending message and verifies it. If the verification is successful, generating the fourth combined message and storing it specifically includes the following steps:

[0036] The payee receives the second sending message and verifies the transaction time and the sixth signature. If the verification fails, the transaction fails. If the verification is successful, a new fourth combined message is generated, and the new fourth combined message and the second sending message are stored. At the same time, the digital currency in the transaction is taken out and stored, marked as unconfirmed by the central bank.

[0037] Further, in S4, using the commercial bank and the central bank to confirm the transaction in the online state specifically includes the following steps:

[0038] S41: The payee and the payee commercial bank perform identity authentication and obtain a session key;

[0039] S42: The payee sends the new fourth combined message, the second sending message, and the signatures of the two to the payee commercial bank;

[0040] S43: The payee commercial bank verifies the signature and the new fourth combined message. If the verification fails, the transaction fails. If the verification is successful, the true identity IDB of the payee is confirmed TRUE , and the information with the second sending message and the payee's true identity IDB TRUE is sent to the central bank;

[0041] S44: The central bank verifies the true identity IDM and the signature of the trusted intermediary in the second sending message. If the verification fails, the transaction fails. If the verification is successful, the true identity IDB of the payee is stored TRUEand the transaction, and send the second sending message to the payer's commercial bank;

[0042] S45. The payer's commercial bank receives the second sending message and verifies the true identity IDM and signature of the trusted intermediary. If the verification fails, the transaction fails. If the verification is successful, it decrypts the encrypted message to obtain a new second combined message, and verifies the new second combined message. If the verification fails, the transaction fails. If the verification is successful, the payer's commercial bank obtains the true identity IDA of the payer TRUE , and will use the true identity IDA of the payer TRUE , the anonymous identity IDB of the payee and the transaction are stored as a complete transaction entry. At the same time, the payer's commercial bank will send the transaction result to the central bank;

[0043] S46. The central bank stores the true identity IDA of the payer TRUE , the true identity IDB of the payee TRUE and the transaction as a complete transaction entry, and sends the transaction result to the payee's commercial bank;

[0044] S47. The payee's commercial bank stores the anonymous identity IDA of the payer, the true identity IDB of the payee TRUE and the transaction as a complete transaction entry, and sends the transaction result to the payee;

[0045] S48. The payee receives the transaction result and confirms that the transaction is successful. At the same time, it deletes the stored new fourth combined message and the second sending message, and finds the digital currency in the stored transaction and marks it as confirmed by the central bank.

[0046] According to another aspect of the present invention, an anonymous dual off-line transaction system based on ID cryptography and a trusted intermediary is provided. The system includes a central bank, a payer's commercial bank, a payee's commercial bank, a payer, a payee and a trusted intermediary. The payer corresponds to the payer's commercial bank, the payee corresponds to the payee's commercial bank, and the trusted intermediary communicates with both the payer and the payee through short-range communication;

[0047] Among them, the central bank is equipped with a key management server based on ID cryptography, and the trusted intermediary is a trusted infrastructure without network connection function. The trusted infrastructure includes but is not limited to digital currency ATMs, digital currency POS machines, and digital currency transaction devices held by trusted merchants.

[0048] The beneficial effects of the present invention are as follows: By using the present invention, anonymous double-offline transactions of digital currency can be achieved, enabling the payer and the payee to use a trusted intermediary to complete anonymous identity transactions during the double-offline transaction stage, and then cooperating with commercial banks and central banks to confirm the transactions during the online transaction stage. The payee can then use the digital currency obtained in the offline transaction. Compared with the prior art, the present invention can better achieve anonymous double-offline transactions of digital currency through the use of ID cryptography and a trusted intermediary, thereby better protecting the privacy information of users and making transactions (especially double-offline transactions) more secure. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0050] Figure 1 is a flowchart of an anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to an embodiment of the present invention;

[0051] Figure 2 is a structural diagram of an anonymous double-offline transaction system based on ID cryptography and a trusted intermediary according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] To further illustrate the embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0053] According to an embodiment of the present invention, an anonymous double-offline transaction method and system based on ID cryptography and a trusted intermediary are provided.

[0054] Now, the present invention will be further described in conjunction with the drawings and specific embodiments. As Figure 1 shown, according to an embodiment of the present invention, an anonymous double-offline transaction method based on ID cryptography and a trusted intermediary is provided. The method includes the following steps:

[0055] S1. Preparatory stage: The key management server KMS issues keys based on ID cryptography to the payer and the payee;

[0056] Among them, the S1 includes the following steps:

[0057] When the key management server KMS issues system public and private keys to the payer / receiver, it takes a random number as the system private key, calculates the corresponding system public key based on this system private key, and stores this system private key at the key management server;

[0058] Specifically, taking the payer A as an example, when the key management server KMS issues system public and private keys to the payer A, it takes a random number SKMS as the system private key, and calculates the corresponding system public key PKMS = SKMS * P (P is a system parameter) based on this system private key SKMS, and stores this system private key PKMS at the key management server KMS;

[0059] When the key management server KMS issues public and private keys to the payer / receiver, it takes a random number as the true identity ID of the payer / receiver, calculates the corresponding public key based on this true identity ID, and calculates the corresponding private key based on this public key;

[0060] Specifically, taking the payer A as an example, when the key management server KMS issues public and private keys to the payer A, it takes a random number as the true identity IDA of the payer TRUE , based on this true identity IDA TRUE calculate the corresponding public key PKA = H(IDA TRUE ) [H(*) is a hash algorithm], and calculate the corresponding private key SKA = SKMS * PKA based on this public key PKA.

[0061] S2. Preparation stage: Use a communication method to achieve short-range communication between the trusted intermediary and the payer and the receiver;

[0062] Among them, S2 includes the following steps:

[0063] S21. Use a communication method to achieve short-range communication between the trusted intermediary and the payer;

[0064] Specifically, M sends (the first combined message) MA = TA || IDM || SIGN(TA || IDM, SKM) to A, where SIGN(m, sk) is to sign the message m using the private key sk, the same below;

[0065] A obtains the ID of M from M's RFID, device body or screen, and verifies whether it is the same as IDM;

[0066] A verifies (the first timestamp) TA and the signature (the first signature), if the verification fails, the transaction fails, otherwise A recognizes M as the owner of IDM;

[0067] A generates its own anonymous identity IDA, preferably a true random number;

[0068] and send (the second combined message) AM = TA||IDA||SIGN(TA||IDA, SKA)||ENC(IDA TRUE , PKM) to M, where ENC(m, pk) is to encrypt the message m using the public key pk, the same hereinafter;

[0069] M decrypts the real identity IDA TRUE , verifies (the second timestamp) TA and the signature (the second signature), if the verification fails, the transaction fails, otherwise M recognizes A as the owner of IDA TRUE ;

[0070] S22. Use the communication method to implement the short - distance communication between the trusted intermediary and the payee;

[0071] Among them, the method of short - distance communication between the payee and the trusted intermediary is the same as that between the payer and the trusted intermediary. Specifically, M sends (the third combined message) MB = TB||IDM||SIGN(TB||IDM, SKM) to B, and B verifies (the third timestamp) TB and the signature (the third signature);

[0072] B generates its own anonymous identity IDB and sends (the fourth combined message)

[0073] BM = TB||IDB||SIGN(TB||IDB, SKB)||ENC(IDB TRUE , PKM) to M, and M decrypts the real identity IDB TRUE , and verifies (the fourth timestamp) TB and the signature (the fourth signature).

[0074] S3. Double - offline transaction stage: Complete the double - offline transaction between the payer and the payee in the offline state through the trusted intermediary;

[0075] Among them, S3 includes the following steps:

[0076] Specifically, M sends (the fifth combined message) MAB = TAB||IDB||SIGN(TAB||IDB, SKM) to A;

[0077] A verifies (the fifth timestamp) TAB and the signature (the fifth signature), if the verification fails, the transaction fails, otherwise A recognizes IDB as the payee;

[0078] A sends (the first sending message) TX||SIGN(TX, SKA) to M (sent in plaintext or encrypted with the recipient's public key), and TX contains the transaction time T, IDA, IDB, digital currency;

[0079] M verifies the transaction. If the verification fails, the transaction fails; otherwise, the transaction continues.

[0080] M generates a new second combined message AM’ = TA || IDA || SIGN(TA || IDA, SKA) || IDA TRUE ;

[0081] The data MAS sent to AS is MAS = ENC(AM’, PKAS);

[0082] M sends the second sending message MBtx = TX || MAS || SIGN(TX || MAS, SKM) || IDM to B (sent in plaintext or encrypted with the recipient's public key);

[0083] B verifies T (transaction time) and the signature (the sixth signature). If the verification fails, the transaction fails; otherwise, the transaction continues.

[0084] B generates a new fourth combined message BM’ = TB || IDB || SIGN(TB || IDB, SKB) || IDB TRUE , stores BM’ || MBtx;

[0085] Retrieves and stores the digital currency in TX, marked as unconfirmed by the central bank.

[0086] S4. Online transaction stage: The transaction is confirmed by the commercial bank and the central bank in the online state;

[0087] Among them, S4 includes the following steps:

[0088] S41. B and BS perform identity authentication and obtain a session key;

[0089] S42. B sends BM’ || MBtx || SIGN(BM’ || MBtx, SKB) to BS;

[0090] S43. BS verifies the signature and BM’. If the verification fails, the transaction fails; otherwise, the transaction continues;

[0091] BS confirms the true identity IDB of B TRUE ;

[0092] BS sends MBtx || IDB TRUE to S;

[0093] S44. S verifies IDM and the signature. If the verification fails, the transaction fails; otherwise, the transaction continues;

[0094] S stores IDB TRUE || TX;

[0095] S sends MBtx to AS;

[0096] S45. AS verifies the IDM and signature. If the verification fails, the transaction fails; otherwise, the transaction continues.

[0097] AS decrypts MAS to obtain AM'.

[0098] AS verifies AM'. If the verification fails, the transaction fails; otherwise, the transaction continues.

[0099] AS obtains the true identity IDA of A TRUE ;

[0100] AS stores IDA TRUE ||IDB||TX is a complete transaction entry, but the true identity of B is unknown;

[0101] AS sends the transaction result RET||IDA TRUE to S, where RET is success or failure;

[0102] S46. S stores IDA TRUE ||IDB TRUE ||TX is a complete transaction entry, that is, S knows the true identities of A and B;

[0103] S sends RET to BS;

[0104] S47. BS stores IDA||IDB TRUE ||TX is a complete transaction entry, but the true identity of A is unknown;

[0105] BS sends RET to B;

[0106] S48. B confirms the transaction is successful, deletes the stored BM'||MBtx, and finds the digital currency in the stored TX, marks it as confirmed by the central bank, and can be used normally later.

[0107] According to another aspect of the present invention, as Figure 2 shown, an anonymous double-offline transaction system based on ID cryptography and a trusted intermediary is provided. The system includes a central bank S, a remitting commercial bank AS, a receiving commercial bank BS, a remitter A, a receiver B, and a trusted intermediary M. The remitter corresponds to the remitting commercial bank, the receiver corresponds to the receiving commercial bank, and the trusted intermediary communicates with both the remitter and the receiver through short-range communication;

[0108] Among them, the central bank is equipped with a key management server KMS based on ID cryptography. KMS issues keys based on ID cryptography to all users. Taking the client of payer A as an example, KMS randomly selects SKMS as the system private key, calculates the system public key PKMS = SKMS * P (P is the system parameter), and KMS randomly selects IDA for A. TRUE , calculates the public key PKA = H(IDA TRUE ) [H(*) is the hash algorithm], and the private key SKA = SKMS * PKA. The system private key SKMS is only stored at KMS.

[0109] The trusted intermediary M is a trusted infrastructure, such as a digital currency ATM, a digital currency POS machine, a digital currency trading device held by a trusted merchant, etc. It has no networking function and does not store the received certificates to prevent user information leakage. A communicates with M at a short distance, and M communicates with B at a short distance.

[0110] In summary, by means of the above technical solutions of the present invention, through the use of the present invention, anonymous double-offline transactions of digital currency can be realized, enabling the payer and the payee to use a trusted intermediary to complete anonymous identity transactions during the double-offline transaction stage, and then cooperating with commercial banks and the central bank to confirm the transactions during the online transaction stage. The payee can then use the digital currency obtained in the offline transaction. Compared with the prior art, the present invention can better realize anonymous double-offline transactions of digital currency through the use of ID cryptography and a trusted intermediary, thereby better protecting the privacy information of users and making transactions (especially double-offline transactions) more secure.

[0111] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0112] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An anonymous double-offline transaction method based on ID cryptography and a trusted intermediary, characterized in that, The method includes the following steps: S1. Pre - preparation stage: The key management server issues keys based on ID cryptography to the payer and the payee. S2. Preparation stage: Use a communication method to achieve short - range communication between the trusted intermediary and the payer and the payee. S3. Double - offline transaction stage: The trusted intermediary completes the double - offline transaction between the payer and the payee in an offline state. S4. Online transaction stage: The commercial bank and the central bank are used to confirm the transaction in an online state. Among them, when the key management server issues the system public and private keys to the payer / payee, a random number is taken as the system private key, and the corresponding system public key is calculated based on this system private key, and the system private key is stored at the key management server. When the key management server issues public and private keys to the payer / payee, a random number is taken as the real identity ID of the payer / payee, the corresponding public key is calculated based on this real identity ID, and the corresponding private key is calculated based on this public key. The use of the communication method in S2 to achieve short - range communication between the trusted intermediary and the payer and the payee includes the following steps: S21. Use a communication method to achieve short - range communication between the trusted intermediary and the payer. S22. Use a communication method to achieve short - range communication between the trusted intermediary and the payee. The use of the communication method in S21 to achieve short - range communication between the trusted intermediary and the payer specifically includes the following steps: S211. The trusted intermediary generates a first combined message and sends it to the payer. S212. The payer receives the first combined message, obtains the identity ID of the trusted intermediary, and verifies whether it is the same as the real identity IDM of the trusted intermediary. At the same time, the payer verifies the first timestamp and the first signature. If the verification fails, the transaction fails; if the verification is successful, the payer recognizes the trusted intermediary as the owner of the real identity IDM of the trusted intermediary. S213. The payer generates its own anonymous identity IDA and a second combined message, and sends the second combined message to the trusted intermediary. S214. The trusted intermediary receives the second combined message and decrypts the true identity IDA of the remitter TRUE , verifies the second timestamp and the second signature. If the verification fails, the transaction fails. If the verification is successful, the remitter is recognized as the owner of the true identity IDA of the remitter TRUE ; The use of the communication method in S22 to achieve short - range communication between the trusted intermediary and the payee specifically includes the following steps: S221. The trusted intermediary generates a third combined message and sends it to the payee. S222. The payee receives the third combined message, obtains the identity ID of the trusted intermediary, and verifies whether it is the same as the real identity IDM of the trusted intermediary. At the same time, the payee verifies the third timestamp and the third signature. If the verification fails, the transaction fails; if the verification is successful, the payee recognizes the trusted intermediary as the owner of the real identity IDM of the trusted intermediary. S223. The payee generates its own anonymous identity IDB and a fourth combined message, and sends the fourth combined message to the trusted intermediary. S224. The trusted intermediary receives the fourth combined message and decrypts the true identity IDB of the payee. TRUE , verifies the fourth timestamp and the fourth signature. If the verification fails, the transaction fails. If the verification succeeds, the payee is recognized as the owner of the true identity IDB of the payee. TRUE .

2. The anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to claim 1, wherein, The completion of the double - offline transaction between the payer and the payee by the trusted intermediary in an offline state in S3 includes the following steps: S31. The trusted intermediary generates a fifth combined message and sends it to the payer. S32. The remitter receives the fifth combined message for verification. If the verification is successful, a first sending message is generated and sent to the trusted intermediary. S33. The trusted intermediary receives the first sending message and conducts verification. If the verification is successful, a second sending message is generated and sent to the payee. S34. The payee receives the second sending message and conducts verification. If the verification is successful, a new fourth combined message is generated and stored.

3. The anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to claim 2, characterized in that The specific steps of the remitter in S32 receiving the fifth combined message for verification and generating a first sending message to send to the trusted intermediary if the verification is successful are as follows: The remitter receives the fifth combined message and verifies the fifth timestamp and the fifth signature. If the verification fails, the transaction fails. If the verification is successful, the user with the payee's anonymous identity IDB is recognized as the payee. At the same time, the remitter sends the first sending message containing the transaction time, the remitter's anonymous identity IDA, the payee's anonymous identity IDB, and the digital currency to the trusted intermediary.

4. The anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to claim 2, wherein The specific steps of the trusted intermediary in S33 receiving the first sending message and generating a second sending message to send to the payee if the verification is successful are as follows: The trusted intermediary receives the first sending message and conducts verification. If the verification fails, the transaction fails. If the verification is successful, a new second combined message is generated. The public key of the remitter's corresponding remitter commercial bank is used to encrypt the new second combined message to obtain an encrypted message and send it to the remitter commercial bank. At the same time, the trusted intermediary generates a second sending message and sends it to the payee.

5. The anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to claim 2, wherein, The specific steps of the payee in S34 receiving the second sending message and generating a fourth combined message to store if the verification is successful are as follows: The payee receives the second sending message and verifies the transaction time and the sixth signature. If the verification fails, the transaction fails. If the verification is successful, a new fourth combined message is generated, and the new fourth combined message and the second sending message are stored. At the same time, the digital currency in the transaction is taken out and stored, marked as unconfirmed by the central bank.

6. The anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to claim 1, wherein, The specific steps of using the commercial bank and the central bank to confirm the transaction in the online state in S4 are as follows: S41. Identity authentication is carried out between the payee and the payee commercial bank to obtain a session key. S42. The payee sends the new fourth combined message, the second sending message, and the signatures of the two to the payee commercial bank. S43. The receiving commercial bank verifies the signature and the new fourth combined message. If the verification fails, the transaction fails; if the verification is successful, the true identity IDB of the receiving party is confirmed. TRUE , and sends the information with the second sending message and the true identity IDB of the receiving party TRUE to the central bank. S44. The central bank verifies the true identity IDM and signature of the trusted intermediary in the second sending message. If the verification fails, the transaction fails. If the verification is successful, it stores the true identity IDB of the payee TRUE and the transaction, and sends the second sending message to the payer's commercial bank; S45. The remitting bank receives the second sending message, verifies the true identity IDM and signature of the trusted intermediary. If the verification fails, the transaction fails. If the verification succeeds, it decrypts the encrypted message to obtain a new second combined message, and verifies the new second combined message. If the verification fails, the transaction fails. If the verification succeeds, the remitting bank obtains the true identity IDA of the remitter. TRUE , and the true identity IDA of the remitter TRUE , the anonymous identity IDB of the payee and the transaction are stored as a complete transaction entry. At the same time, the remitting bank sends the transaction result to the central bank; S46. The central bank stores the true identity IDA of the remitter TRUE , the true identity IDB of the payee TRUE and the transaction as a complete transaction entry, and sends the transaction result to the commercial bank of the payee; S47. The receiving commercial bank stores the anonymous identity IDA of the remitting party and the real identity IDB of the receiving party TRUE and the transaction as a complete transaction entry, and sends the transaction result to the receiving party; S48. The payee receives the transaction result and confirms the success of the transaction. At the same time, the stored new fourth combined message and the second sending message are deleted, and the digital currency in the stored transaction is found and marked as confirmed by the central bank.

7. An anonymous double-offline transaction system based on ID cryptography and a trusted intermediary, for implementing the steps of the anonymous double-offline transaction method based on ID cryptography and a trusted intermediary according to any one of claims 1-6, characterized in that, The system includes a central bank, a remitter commercial bank, a payee commercial bank, a remitter, a payee, and a trusted intermediary. The remitter corresponds to the remitter commercial bank, the payee corresponds to the payee commercial bank, and the trusted intermediary communicates with both the remitter and the payee through short-range communication. Among them, the central bank is equipped with a key management server based on identity cryptography, and the trusted intermediary is a trusted infrastructure without networking capabilities, which includes but is not limited to digital currency ATMs, digital currency POS machines, and digital currency trading devices held by trusted merchants.

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