A data encryption hosting system and method based on blockchain

Abstract

The present invention provides a blockchain-based data encryption escrow system and method, belonging to the field of data encryption. The system includes: an initialization module, a guardian committee, a sender, and a receiver; each member of the guardian committee, the sender, and the receiver are nodes in the blockchain; the guardian committee determines a threshold key pair, a group public-private key pair, and a threshold value for each member based on a distributed key generation method according to a third generator; the sender encrypts target data according to the third generator, a random number, a second generator, the receiver's public key, and the group public key to obtain an initial ciphertext; each member calculates a decryption share based on the private key share and the first ciphertext; the receiver reconstructs the third ciphertext using a Lagrange interpolation method based on the decryption share and the threshold value, and obtains the target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator. The present invention improves the security of the encryption system and the privacy of the ciphertext.

Description

Technical Field

[0001] The present invention relates to the field of data encryption, and in particular to a data encryption hosting system and method based on blockchain. Background Art

[0002] As blockchain applications expand, they are being widely used in research for scenarios such as data encryption and escrow. Researchers have introduced the concept of threshold cryptography within traditional group data encryption. Threshold cryptography, which enables multi-user collaborative decryption and signing, offers inherent advantages over traditional public-key cryptography in ensuring data security, privacy protection, and identity authentication in group environments. Threshold cryptography distributes private key information among multiple users, preventing a successful decryption attempt by fewer than a threshold number of users. Only a combined decryption effort of at least a threshold number of users can recover the message.

[0003] Traditional threshold-based single-key encryption is used for collective secret protection. Encryption by different groups requires complex distributed key generation processes. The benefits of threshold encryption don't easily translate to individual users encrypting data. Therefore, designing a more secure data encryption scheme that is user-friendly while leveraging the advantages of threshold encryption is an important research direction. Summary of the Invention

[0004] The purpose of the present invention is to provide a blockchain-based data encryption hosting system and method, which can improve the security of the encryption system and the privacy of the ciphertext.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A data encryption custody system based on blockchain, comprising: an initialization module, a guardian committee, a sender, and a receiver; the guardian committee comprises multiple members; each member of the guardian committee, the sender, and the receiver are nodes in the blockchain;

[0007] The initialization module is used to initialize system parameters; the system parameters include a first generator, a second generator, a third generator, a receiver's public and private key pair, and a random number;

[0008] The guardian committee is configured to determine, based on the third generator and a distributed key generation method, a threshold key pair, a group public-private key pair, and a threshold value for each member; the threshold key pair includes a private key and a private key share of the corresponding member;

[0009] The sender is configured to encrypt the target data according to the third generator, the random number, the second generator, the receiver's public key, and the group public key to obtain an initial ciphertext; the initial ciphertext includes a first ciphertext and a second ciphertext;

[0010] The receiving party is used to send a decryption request to the Guardian Committee;

[0011] Each member of the guardian committee is configured to calculate the member's decryption share based on the member's private key share and the first ciphertext, and send the decryption share to the recipient;

[0012] The receiver is further configured to reconstruct a third ciphertext using the Lagrange interpolation method based on the received decryption share and the threshold value, and obtain target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator.

[0013] Optionally, the initialization module includes:

[0014] a prime number selection unit, configured to randomly select a first prime number and a plurality of second prime numbers;

[0015] a first generating unit, connected to the prime number selecting unit, for calculating a first generator according to the first prime number and a plurality of second prime numbers;

[0016] a group determining unit connected to the first generating unit, configured to determine a positive integer group and a third generator based on the first generator; the positive integer group is a positive integer from 1 to Q-1; the order of the third generator is Q-1, where Q is the first generator;

[0017] an intermediate generator unit, connected to the group determination unit, and configured to determine an intermediate generator set, a random number, and a recipient private key from the group of positive integers; the intermediate generator set includes a plurality of intermediate generators, the number of intermediate generators is the same as the number of second prime numbers, and the order of each intermediate generator corresponds to each second prime number;

[0018] a second generating unit, connected to the intermediate generating unit, and configured to determine a second generator according to the intermediate generator set;

[0019] The receiver public key determination unit is connected to the group determination unit and the intermediate generation unit respectively, and is used to determine the receiver public key according to the third generator and the receiver private key.

[0020] Optionally, the first generating unit adopts the formula Calculate the first generator; where q is the first prime number, k is the number of second prime numbers, and p i is the i-th second prime number.

[0021] Optionally, the second generating unit adopts the formula Determine the second generator; where g is the second generator, k is the number of second prime numbers, and gi is the i-th intermediate generator.

[0022] Optionally, the first ciphertext is: CN1=h r ; The second ciphertext is: CN2 = g M ·UPK r ·PK r ;

[0023] Among them, CN1 is the first ciphertext, CN2 is the second ciphertext, h is the third generator, r is a random number, g is the second generator, M is the target data, UPK is the recipient's public key, and PK is the group public key.

[0024] Alternatively, use the formula Calculated Member P i The decryption share of i For member P i The decryption share, CN1 is the first ciphertext, x i For member P i The private key share.

[0025] Optionally, when the number of decryption shares received by the receiver is greater than the threshold value, the receiver reconstructs the third ciphertext using the Glagrange interpolation method based on the received decryption shares, otherwise the decryption fails.

[0026] Optionally, the recipient obtains the target data according to the first ciphertext, the second ciphertext, the third ciphertext, the recipient's private key, and the second generator, specifically including:

[0027] According to the second ciphertext and the third ciphertext, the formula M'=CN2 / RM=g is used. M ·UPK r Determine the fourth ciphertext; where M' is the fourth ciphertext, CN2 is the second ciphertext, and RM is the third ciphertext;

[0028] According to the fourth ciphertext, the first ciphertext and the recipient's private key, the formula M' / CN1 is used y =g M Calculate the fifth ciphertext; where g M is the fifth ciphertext, CN1 is the first ciphertext, and y is the recipient’s private key;

[0029] According to the second generator and the fifth ciphertext, the target data is determined using the Chinese remainder theorem.

[0030] To achieve the above object, the present invention also provides the following solution:

[0031] A data encryption custody method based on blockchain, comprising:

[0032] Initialize system parameters; the system parameters include the first generator, the second generator, the third generator, the recipient's public and private key pair, and a random number;

[0033] The guardian committee determines, based on the third generator and a distributed key generation method, a threshold key pair, a group public-private key pair, and a threshold value for each member; the threshold key pair includes a private key and a private key share of the corresponding member; and the guardian committee includes multiple members.

[0034] The sender encrypts the target data according to the third generator, the random number, the second generator, the receiver's public key, and the group public key to obtain an initial ciphertext; the initial ciphertext includes the first ciphertext and the second ciphertext;

[0035] The receiving party sends a decryption request to the Guardian Committee;

[0036] For any member of the guardian committee, calculate the member's decryption share based on the member's private key share and the first ciphertext, and send the decryption share to the recipient;

[0037] The receiver reconstructs the third ciphertext using the Lagrange interpolation method based on the received decryption share and the threshold value, and obtains the target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key and the second generator; each member of the guardian committee, the sender and the receiver are all nodes in the blockchain.

[0038] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0039] Based on the traditional public key encryption and private key decryption process, the present invention adds a threshold guardian data trusteeship encryption process, and encrypts the ciphertext after plaintext encryption for the second time using the threshold public key. During decryption, the recipient must first be verified by the guardian committee, and then the decryption share is provided by members who meet the threshold value to decrypt the initial ciphertext, and then the final target data is decrypted using the recipient's private key, so that attackers who intercept the recipient's public and private keys cannot crack the encrypted data, further ensuring the security of the encryption and the privacy of the encrypted ciphertext. Threshold encryption is used as the encryption method of the guardian committee. Threshold encryption has a more complex security model than traditional public key cryptography, which improves the security of the password. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is a schematic diagram of the blockchain-based data encryption hosting system of the present invention;

[0042] Figure 2 A schematic diagram of the process of data encryption and hosting according to the present invention;

[0043] Figure 3 This is a flowchart of the blockchain-based data encryption and custody method of the present invention. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0045] Data custody encryption is a new encryption construction model derived from the blockchain scenario. Based on a thorough study of cryptographic threshold encryption methods and blockchain technology, the present invention provides a data encryption custody system and method based on blockchain. It integrates dual public key encryption into the blockchain, and provides data encryption custody services to users with encryption needs, facilitating a more secure data encryption process between users. At the same time, a decentralized third-party supervision group is introduced to provide custody services based on blockchain. The guardian group uses thresholds to perform secondary encryption and decryption on the data, reducing the risk of ciphertext attacks, improving the security of the encryption process, and forming a complete blockchain custody service to provide more reliable and efficient protection for the encryption process.

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Example 1

[0048] like Figure 1 As shown, this embodiment provides a blockchain-based data encryption and escrow system, comprising an initialization module, a guardian committee, a sender, and a receiver. The guardian committee includes multiple members. Each member of the guardian committee, the sender, and the receiver are nodes in the blockchain. The sender selects a secret data for encrypted escrow, which is then encrypted by a group of blockchain committee members. The receiver then requests decryption of the data. The entire process is based on blockchain activity.

[0049] The initialization module is used to initialize system parameters, including the first generator, the second generator, the third generator, the receiver's public and private key pair, and a random number.

[0050] Specifically, the initialization module includes: a prime number selection unit, a first generation unit, a group determination unit, an intermediate generation unit, a second generation unit and a receiver public key determination unit.

[0051] The prime number selection unit is used to randomly select a first prime number q and a plurality of second prime numbers {p1, p2, ..., p k The first prime number is greater than the second prime number, that is, the first prime number is a large prime number and the second prime number is a small prime number. In addition, you can also select the security parameter 1 λ .

[0052] The first generating unit is connected to the prime number selecting unit, and the first generating unit is used to use the formula according to the first prime number and multiple second prime numbers. Calculate the first generator. Where q is the first prime number, k is the number of second prime numbers, p i is the i-th second prime number.

[0053] A group determination unit is connected to the first generation unit, and the group determination unit is used to determine a positive integer group based on the first generator. And the third generator h. Positive integer group is a positive integer from 1 to Q-1. The order of the third generator h is Q-1, and Q is the first generator.

[0054] The intermediate generation unit is connected to the group determination unit, and is used to determine the intermediate generator set {g1, g2, ..., g k The intermediate generator set includes multiple intermediate generators, the number of intermediate generators is the same as the number of the second prime number, and each intermediate generator {g1, g2, ..., g k} corresponds to the order of the second prime numbers {p1,p2,…,p k}.

[0055] The second generating unit is connected to the intermediate generating unit, and the second generating unit is used to use the formula according to the intermediate generating element set. Determine the second generator. Where g is the second generator, k is the number of the second prime number, g i is the i-th intermediate generator.

[0056] The receiver public key determination unit is connected to the group determination unit and the intermediate generation unit respectively, and the receiver public key determination unit is used to determine the receiver public key h according to the third generator h and the receiver private key y. y .

[0057] The initialization phase is to initialize the parameters used subsequently. Various prime number generators are used for group calculations. The recipient's public and private key pairs already exist in actual applications. After one initialization, it can undertake multiple encryption hosting tasks.

[0058] The guardian committee is used to determine the threshold key pair of each member based on the third generator and the distributed key generation method. Group public and private keys The threshold key pair includes the private key and private key share x of the corresponding member. i .

[0059] Assume that there are n members in the guardian committee, denoted as P1, P2, ..., P n , the members of the Guardian Committee pre-run the DKG (distributed key generation) method to determine the threshold key pair and the group public key and private key pair of each member. Here, the private key shares of each member are x1, x2, ..., x n It satisfies the relevant properties of the t-order secret sharing polynomial, that is, more than t members can use the shares together to recover the group's private key x0.

[0060] This stage is used for the initialization process of the guardian committee members. Before starting to undertake the threshold decryption trusteeship task, the determined committee members must generate the group's threshold public and private key pairs and the threshold private key share of each node through an established method, which will be used for subsequent decryption operations of the encrypted content.

[0061] The present invention constructs a key encryption trusteeship scheme based on Paillier threshold key and ElGamal encryption. The secret sharing committee is also a guardian encryption committee and supports dynamic update and replacement of committee members.

[0062] The sender is configured to encrypt the target data based on the third generator, the random number, the second generator, the recipient's public key, and the group public key to obtain an initial ciphertext. The initial ciphertext includes the first ciphertext and the second ciphertext. In a specific embodiment, the target data can be a private key in the blockchain field, financial transaction data, important project data, etc.

[0063] Specifically, the sender needs to perform two encryption operations on the target data M, using the receiver's public key UPK=h y and group public key The target data M is encrypted to generate a combined ciphertext C = (CN1, CN2) and sent to the recipient. In this embodiment, the Lifted ElGamal encryption algorithm is used to generate the first ciphertext and the second ciphertext.

[0064] Among them, the first ciphertext is: CN1=h r The second ciphertext is: Among them, CN1 is the first ciphertext, CN2 is the second ciphertext, h is the third generator, r is a random number, g is the second generator, M is the target data, UPK is the recipient's public key, and PK is the group public key.

[0065] The receiver sends a decryption request to the Guardian Committee. After receiving the sender's initial ciphertext, the receiver must first seek the Guardian Committee's help when decryption is required. The receiver sends its identity information to the Guardian Committee to request the decryption of the initial ciphertext.

[0066] Each member of the Guardian Committee calculates their decryption share based on their private key share and the first ciphertext, and sends the calculated share to the recipient. Each member of the Guardian Committee independently verifies whether the message can be decrypted. Once verified, they use their private key share to calculate the decryption share, facilitating subsequent secret recovery.

[0067] Specifically, the formula Calculated Member P i The decryption share of i For member P i The decryption share, CN1 is the first ciphertext, x i For member P i The private key share.

[0068] The receiver is also used to reconstruct the third ciphertext based on the received decryption share and the threshold value using the Lagrange interpolation method, and obtain the target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key and the second generator.

[0069] When the number of decryption shares received by the receiver is greater than the threshold value, the receiver reconstructs the third ciphertext based on the received decryption shares using the Glagrange interpolation method, otherwise the decryption fails. Specifically, the receiver collects the decryption shares E of the members of the guardian committee. i , when the correct decryption share E i When the number exceeds the threshold value t+1, the third ciphertext RM can be reconstructed by Lagrange interpolation method:

[0070]

[0071] Among them, U is the correct decryption share set, LA i,0 For member P iThe Lagrange coefficient corresponding to the 0th secret position. The secret position is a curve formed by a polynomial f(x), where different positions of x correspond to different points on the curve. f(0) is the target data, f(1) is the share of the first member, and f(2) is the share of the second member.

[0072] Due to the previous DKG process, the members of the guardian committee have formed a set of group public-private key pairs and their corresponding public-private key shares. The private key shares exceeding the threshold value can be used to reconstruct the group private key through the Lagrange interpolation method. Therefore, the decryption shares that have passed the verification and exceed the threshold value can be used together to reconstruct a third ciphertext RM of the group decryption.

[0073] Furthermore, the receiver obtains the target data according to the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator, specifically including:

[0074] According to the second ciphertext and the third ciphertext, the formula M'=CN2 / RM=g is used. M ·UPK r The ciphertext encrypted by the receiver's public key UPK is calculated, that is, the fourth ciphertext M'.

[0075] According to the fourth ciphertext, the first ciphertext and the recipient's private key, the formula M' / CN1 is used y =M' / (h r ) y =M' / UPK r =g M Calculate the fifth ciphertext g M That is, decryption is performed using the recipient's private key USK=y.

[0076] According to the second generator and the fifth ciphertext, the target data is determined using the Chinese remainder theorem.

[0077] Specifically, since the intermediate generators {g1,g2,…,g k} has an order of {p1,p2,…,p k}, For i∈{1,…,k}, the receiver can use the following formula to calculate the first intermediate variable p' i and the second intermediate variable e i :

[0078]

[0079]

[0080] Since the intermediate generator g i The order is p i , p iis a small prime number, and we can get e by solving the discrete logarithm. i =M·p' i , and then we get k equations M=(p' i ) -1 e i mod p i The receiver uses the Chinese remainder theorem to solve the k equations and obtain the final target data M.

[0081] like Figure 2 The figure shows a schematic diagram of the process of data encryption trusteeship of the present invention, which includes 6 stages: system initialization stage, guardian initialization stage, message encryption stage, guardian threshold decryption stage, decryption reconstruction stage and message decryption stage.

[0082] In the research of blockchain cryptography, the present invention encrypts a data secret and hosts it on the blockchain, such as encrypting and hosting the private key in the blockchain field, or encrypting and hosting other important text file information, which can be applied in future security fields.

[0083] Example 2

[0084] Corresponding to the method provided in Example 1, this embodiment provides a data encryption custody method based on blockchain.

[0085] like Figure 3 As shown, the data encryption custody method based on blockchain provided in this embodiment includes:

[0086] S1: Initialize system parameters, including the first generator, the second generator, the third generator, the recipient's public and private key pair, and a random number.

[0087] S2: The Guardian Committee determines the threshold key pair, group public-private key pair, and threshold value for each member based on the third generator and a distributed key generation method. The threshold key pair includes the private key and private key share of the corresponding member; the Guardian Committee includes multiple members.

[0088] S3: The sender encrypts the target data according to the third generator, the random number, the second generator, the receiver's public key, and the group public key to obtain an initial ciphertext, which includes a first ciphertext and a second ciphertext.

[0089] S4: The recipient sends a decryption request to the Guardian Committee.

[0090] S5: For any member of the guardian committee, calculate the member's decryption share based on the member's private key share and the first ciphertext, and send it to the recipient.

[0091] S6: The receiver reconstructs the third ciphertext using the Lagrange interpolation method based on the received decryption share and the threshold value, and obtains the target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator. Each member of the guardian committee, the sender, and the receiver are nodes in the blockchain.

[0092] The beneficial effects of the present invention are:

[0093] (1) The present invention transforms the encryption process into a blockchain-based escrow service, with a decentralized third-party group in the blockchain centrally providing secondary encrypted ciphertext escrow services. This ultimately results in an encryption system with a guardian, which is also a dual public key encryption system. Compared to the prior art, the present invention uses threshold encryption as the encryption method for the group that oversees the escrow party. Threshold encryption has a more complex security model and richer application features than traditional public key encryption, and can construct a more secure cryptographic scheme, ensuring that the cryptographic scheme has greater application applicability.

[0094] (2) Based on the traditional public key encryption and private key decryption process, the present invention adds a threshold guardian data escrow encryption process, and encrypts the ciphertext after plaintext encryption for a second time using the threshold public key. During decryption, the decryptor must first be verified by the guardian group, and then the guardian who meets the threshold value provides a share to decrypt the initial encrypted ciphertext, and then uses his own private key to decrypt the final message, which further ensures the security of encryption and the privacy of the encrypted ciphertext, so that attackers who intercept the user's public and private keys cannot crack the encrypted data information.

[0095] (3) The present invention separates the threshold encryption link from the user, so that individual users can also enjoy the security protection brought by threshold encryption. They do not need to select the encryption group themselves, circumventing the complex DKG process brought about by the change of threshold monitoring groups, and instead choose a data encryption hosting service with integrity, using the excellent characteristics of the blockchain to provide systematic services, further ensuring the security of the encryption system, and enhancing the convenience and operability of the encryption service.

[0096] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0097] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A data encryption hosting system based on blockchain, characterized in that: The blockchain-based data encryption custody system includes: an initialization module, a guardian committee, a sender, and a receiver; the guardian committee includes multiple members; each member of the guardian committee, the sender, and the receiver are nodes in the blockchain; The initialization module is used to initialize system parameters; the system parameters include a first generator, a second generator, a third generator, a receiver's public and private key pair, and a random number; The initialization module includes: a prime number selection unit, configured to randomly select a first prime number and a plurality of second prime numbers; a first generating unit, connected to the prime number selecting unit, for calculating a first generator according to the first prime number and a plurality of second prime numbers; a group determining unit connected to the first generating unit, configured to determine a positive integer group and a third generator based on the first generator; the positive integer group is a positive integer from 1 to Q-1; the order of the third generator is Q-1, where Q is the first generator; an intermediate generator unit, connected to the group determination unit, and configured to determine an intermediate generator set, a random number, and a recipient private key from the group of positive integers; the intermediate generator set includes a plurality of intermediate generators, the number of intermediate generators is the same as the number of second prime numbers, and the order of each intermediate generator corresponds to each second prime number; a second generating unit, connected to the intermediate generating unit, and configured to determine a second generator according to the intermediate generator set; a receiver public key determination unit, connected to the group determination unit and the intermediate generation unit, respectively, for determining the receiver public key based on the third generator and the receiver private key; The guardian committee is configured to determine, based on the third generator and a distributed key generation method, a threshold key pair, a group public-private key pair, and a threshold value for each member; the threshold key pair includes a private key and a private key share of the corresponding member; The sender is configured to encrypt the target data according to the third generator, the random number, the second generator, the receiver's public key, and the group public key to obtain an initial ciphertext; the initial ciphertext includes a first ciphertext and a second ciphertext; The receiving party is used to send a decryption request to the Guardian Committee; Each member of the guardian committee is configured to calculate the member's decryption share based on the member's private key share and the first ciphertext, and send the decryption share to the recipient; The receiver is further configured to reconstruct a third ciphertext using the Lagrange interpolation method based on the received decryption share and the threshold value, and obtain target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator.

2. The data encryption hosting system based on blockchain according to claim 1 is characterized in that: The first generating unit adopts the formula Calculate the first generator; where q is the first prime number, k is the number of second prime numbers, and p i is the i-th second prime number.

3. The data encryption hosting system based on blockchain according to claim 1 is characterized in that: The second generation unit adopts the formula Determine the second generator; where g is the second generator, k is the number of the second prime number, g i is the i-th intermediate generator.

4. The data encryption hosting system based on blockchain according to claim 1 is characterized in that: The first ciphertext is: CN1=h r ; The second ciphertext is: CN2 = g M ·UPK r ·PK r ; Among them, CN1 is the first ciphertext, CN2 is the second ciphertext, h is the third generator, r is a random number, g is the second generator, M is the target data, UPK is the recipient's public key, and PK is the group public key.

5. The blockchain-based data encryption hosting system according to claim 1 is characterized in that: Using the formula Calculated Member P i The decryption share of i For member P i The decryption share, CN1 is the first ciphertext, x i For member P i The private key share.

6. The data encryption hosting system based on blockchain according to claim 1 is characterized in that: When the number of decryption shares received by the receiver is greater than the threshold value, the receiver reconstructs the third ciphertext using the Glagrange interpolation method according to the received decryption shares; otherwise, the decryption fails.

7. The data encryption hosting system based on blockchain according to claim 1 is characterized in that: The receiver obtains target data according to the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key, and the second generator, specifically including: According to the second ciphertext and the third ciphertext, the formula M'=CN2 / RM=g is used. M ·UPK r Determine the fourth ciphertext; where M' is the fourth ciphertext, CN2 is the second ciphertext, and RM is the third ciphertext; According to the fourth ciphertext, the first ciphertext and the recipient's private key, the formula M' / CN1 is used y =g M Calculate the fifth ciphertext; where g M is the fifth ciphertext, g is the second generator, M is the target data, CN1 is the first ciphertext, and y is the recipient's private key; According to the second generator and the fifth ciphertext, the target data is determined using the Chinese remainder theorem.

8. A data encryption hosting method based on blockchain, applying the data encryption hosting system based on blockchain according to any one of claims 1 to 7, characterized in that: The blockchain-based data encryption custody method includes: Initialize system parameters; the system parameters include the first generator, the second generator, the third generator, the recipient's public and private key pair, and a random number; The guardian committee determines, based on the third generator and a distributed key generation method, a threshold key pair, a group public-private key pair, and a threshold value for each member; the threshold key pair includes a private key and a private key share of the corresponding member; and the guardian committee includes multiple members. The sender encrypts the target data according to the third generator, the random number, the second generator, the receiver's public key, and the group public key to obtain an initial ciphertext; the initial ciphertext includes the first ciphertext and the second ciphertext; The receiving party sends a decryption request to the Guardian Committee; For any member of the guardian committee, calculate the member's decryption share based on the member's private key share and the first ciphertext, and send the decryption share to the recipient; The receiver reconstructs the third ciphertext using the Lagrange interpolation method based on the received decryption share and the threshold value, and obtains the target data based on the first ciphertext, the second ciphertext, the third ciphertext, the receiver's private key and the second generator; each member of the guardian committee, the sender and the receiver are all nodes in the blockchain.

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