Cloud data encryption and decryption transmission system and data migration method

Abstract

The invention belongs to the technical field of data transmission methods, and particularly relates to a cloud data encryption and decryption transmission system and a data migration method. The cloud data encryption and decryption transmission system comprises a cloud server side, a user side and a credit side. The cloud server is used for realizing online storage, transmission and deletion of messages such as ciphertexts; the user side has different attributes according to different identities in the data transmission process, and comprises a data storage side and a data request side; the user side attribute access structure is used for hiding an encryption key of source data; the credit end is used for generating and storing a secret key and an encryption and decryption algorithm and providing the secret key and the encryption and decryption algorithm to the user end or the cloud server according to a request. According to the cloud data encryption and decryption transmission system and the data migration method, a system scheme which can be used for cloud data encryption, transmission and migration is provided, and the confidentiality and integrity of data are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of data transmission methods, and in particular relates to a cloud data encryption and decryption transmission system and a data migration method. Background Art

[0002] The development of digital technology has effectively improved the speed and accuracy of social information transmission, and provided the necessary basic conditions for economic development and technological progress. In recent years, with the continuous advancement of digital information technology, the incremental and stock amounts of global data have shown a rapid growth trend. For the vast majority of data users or owners, they generally do not have sufficient data storage and management capabilities. Even professional data management service agencies generally find it difficult to manage and store all data locally. Therefore, distributed storage, cloud storage services and other efficient and flexible storage methods have been rapidly applied. Among them, cloud-based data storage and management services can effectively reduce the use and maintenance costs of data owners and data users, and enhance the liquidity of data. On the other hand, data stored in the cloud often needs to be transmitted through a large number of intermediate nodes between two nodes, and a large amount of data is also stored separately in different nodes. Therefore, the data migration and transmission process often involves a large number of data in and out operations, which leads to great challenges to data security. Summary of the invention

[0003] The object of the present invention is to provide a cloud data encryption and decryption transmission system and a data migration method using trusted transmission and migration management of cloud data.

[0004] To achieve the above purpose, the present invention adopts the following technical solution.

[0005] A cloud data encryption and decryption transmission system, comprising a cloud service end, a user end, and a credit end;

[0006] The cloud server is used to realize the online storage, transmission and deletion of ciphertext and other messages; the user end has different attributes according to its different identities in the data transmission process, including the data storage end and the data request end; the user end attribute access structure is used to hide the encryption key of the source data; the credit end is used to generate and save the secret key, encryption and decryption algorithm and provide it to the user end or cloud server upon request.

[0007] A further improvement or preferred implementation of the aforementioned cloud data encryption and decryption transmission system, wherein the attribute access structure includes a root node, a leaf node, and a threshold node; the leaf node is a subordinate node of the threshold node; the threshold node is connected to the root node through several layers of threshold structures; wherein the node without a subordinate is a leaf node, and has a unique leaf node attribute value A i ; The node with subordinates is a threshold node, which has a logical attribute θ; the logical attribute θ controls the attribute value k of the threshold node θ; If the logical attribute θ = or, then the threshold node attribute value k θ =1; if the logical attribute θ = and, then the threshold node attribute value k θ =n θ ={A θ}, where n θ is the set of attribute values ​​of its child nodes, A θ It is the attribute of its child node; the top node is the root node, which has the migration flag attribute U o If the data request end wants to obtain the data of a leaf node, it needs to have the attribute value set by the node data owner and the root node migration flag attribute U o The attribute value corresponding to the migration state;

[0008] A further improvement or preferred implementation of the aforementioned cloud data encryption and decryption transmission system, the credit end is also used to generate multi-order multiplication cyclic groups G and G T , construct a bilinear pair e(G,G):G×G→G T ;

[0009] For a bilinear pair e(G,G):G×G→G T , the generator of the multi-factorial cyclic group G {g i},satisfy g a ,g b ∈{g i}.

[0010] Based on the above, the present application also provides a cloud data migration method, including the following steps:

[0011] A1. Steps to establish a user-side data system based on attribute access structure

[0012] Based on the attribute access structure, a user-side attribute access structure is established, including a root node, a leaf node and a threshold node; the leaf node is a lower-level node of the threshold node, and the uppermost node is the root node;

[0013] A2. Steps to configure system initial parameters

[0014] Credit end specifies the migration flag attribute U o , generating multi-factorial cyclic groups G and G T , construct a bilinear pair e(G,G):G×G→G T ; Generate hash function H 1 ={0,1}*→G* and Generate random parameters α, β, Create the secret key MSK and execute the secret key parameter keyfor release process, where:

[0015] keyfor=p,G,GT ,g,e(G,G),H 1 ,H 2 ,U o ,e(g,g) α ,g β ,g γ ;

[0016] MSK=(g α ,β,γ);

[0017] where p is a multi-factorial cyclic group G and G T The order of ; g is the generator of the cyclic group G;

[0018] A3. Steps to generate data transmission keys

[0019] Based on the established attribute access structure, establish a node attribute parameter set S = {A i}, for each leaf node attribute A i Assigning random parameters For a property set User j Randomly generated certification mark For the user side User j Select Private Key Calculate and publish the user side User j The public key At the same time, calculate the user j The decryption key in

[0020] User j Private key Set j And the decryption key SK j Send securely to the user end;

[0021] A4. Steps for data encryption and storage

[0022] The data storage end selects a random symmetric encryption key κ∈G according to its own configuration T , use the symmetric encryption algorithm to encrypt the migration data Date and the symmetric key κ; assign the associated secret attribute s to the node θ based on the attribute access structure θ , secret attributes θ Based on its upper node, it obtains and shares with all lower nodes of node θ; specifically: the root node generates a random secret number S', S", S”≠S”’; S” and S”’ are used to generate the migration flag attribute U o ; For any node θ, design k θ-1 degree polynomial f; child nodes of node θ Assigning relatively unique index values Generate secret parameters for child nodes Get child nodes The ciphertext formula is in Refers to the child node Attribute value of

[0023] A5. Steps for verifying data migration messages

[0024] The data storage end uploads the encrypted data to the cloud service end, and the data storage end sends a migration verification message Tran = {User j ,name,U o ,dex,tag,sig};

[0025] Where name refers to the data file name, and dex refers to the lower-level child node ID;

[0026] tag=H 1 (name||U 0 ||dex);

[0027] The cloud server is based on the index value Generate verification information for dex nodes;

[0028] After receiving the migration message Tran, the credit end verifies the legitimacy of the user's identity by using the user's secret key parameter keyfor, that is, whether it satisfies e(tag,Oet j )=e(sig,g); if the verification is passed, the credit end calculates tag'=h 1 (name||U 0 ||dex) and compare it with tag to verify the migration message Tran. If the two are consistent, the verification is successful, and the corresponding message list is generated according to the migration control attribute of the migration message Tran;

[0029] A6. Steps to start data migration

[0030] When the migration request from the data requesting end arrives, the credit end generates a migration token TranT i =H 1 (i) δ ; and send a migration request instruction TranR = (U j ,name,TranT i,index); After receiving the data, the cloud server runs the multi-target tracking algorithm to obtain the data verification information and track the root node of the current data, and start data migration;

[0031] A7. Steps to decrypt data and obtain data content

[0032] Data request end j The retrieval system downloads the ciphertext data and calculates the ciphertext data according to its attribute set S j And user name and other information with decryption key SK j Run the decryption algorithm. The decryption process is based on constructing the attribute access structure from bottom to top, that is, from leaf nodes to root nodes. The specific steps are as follows:

[0033] When the data request end U j The attribute set S j Contains the attribute A of the leaf node θ i , then the decryption calculation formula can be expressed as:

[0034]

[0035] When the data request end U j The attribute set S j The attribute A that does not contain the leaf node θ i , then output JM θ =⊥; For the root node Root, if JM θ ≠⊥ and the migration message Tran passes the verification, then it passes Get the data in the ciphertext.

[0036] Its beneficial effects are:

[0037] The cloud data encryption and decryption transmission system and data migration method of the present application provide a system solution that can be used for cloud data encryption transmission and migration, which is conducive to ensuring the confidentiality and integrity of data. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a functional schematic diagram of each part of the system;

[0039] Figure 2 is a diagram of the attribute access structure. DETAILED DESCRIPTION

[0040] The present invention is described in detail below in conjunction with specific embodiments.

[0041] A cloud data encryption and decryption transmission system of the present application includes a cloud service end, a user end, and a credit end;

[0042] A cloud data encryption and decryption transmission system, comprising a cloud service end, a user end, and a credit end;

[0043] like Figure 1 As shown, the cloud server is used to realize the online storage, transmission and deletion of ciphertext and other messages. Through the cloud server, it can meet the data management and maintenance requests of a large number of user terminals.

[0044] The user end has different attributes according to its different identities in the data transmission process, including the data storage end and the data request end; the user end attribute access structure is used to hide the encryption key of the source data;

[0045] The data storage end refers to the sender provider of data during a data migration and transmission process. These data are generally stored in the local storage space of the user end or its associated trusted storage space. In this application, data is mainly transmitted through the cloud to achieve fast sending and receiving. Since the cloud is unreliable, the data storage end needs to encrypt the data to be sent by combining its own attributes with the encryption scheme provided by the credit end before sending. The data request end is the initiator or receiver of a data migration and transmission. The data request end performs identity tagging based on its own attributes and information such as the ID assigned by the credit end, and obtains data through a process that complies with the trusted end verification procedure.

[0046] The credit end is mainly used to manage the security and parameter control of the entire system, generate and save secret keys, encryption and decryption algorithms, and provide them to the user end or cloud server upon request. Generally, its functions are performed by a system or structure with sufficient credibility and security.

[0047] The following is a detailed description of the data security migration process of the cloud data encryption and decryption transmission system. The specific steps are as follows:

[0048] A1. Establishing a user-side data system based on attribute access structure

[0049] Combination Figure 1 As shown in the figure, a system service structure is established. In order to ensure the credibility of the user end during the process of data passing through each cloud service node or user end, the corresponding attribute access structure is established based on the idea of ​​attribute access structure in this application. The attribute access structure is as follows Figure 2 As shown, in the attribute access structure, the data storage end serves as the root node, and the data request end serves as its leaf node or threshold node, ultimately forming a multi-level attribute access structure. In the attribute access structure, the user end corresponding to any lower-level node can obtain the encrypted data of the root node through the user ends corresponding to its several upper-level nodes. However, in this process, the user end corresponding to any upper-level node needs to perform attribute verification on the user end corresponding to its lower-level node.

[0050] Among them, the most important purpose of the attribute access structure is to hide the encryption key of the source data. Since each user end can only directly verify with the user end corresponding to its parent node and cannot obtain and decrypt across levels, the security and confidentiality of the source data key are effectively guaranteed.

[0051] Generally speaking, the attribute access structure is composed of nodes representing each user terminal. During any data migration and transmission process, each user terminal can be matched with different nodes of the attribute access structure according to its functional role.

[0052] It includes root nodes, leaf nodes and threshold nodes; leaf nodes are subordinate nodes of threshold nodes; threshold nodes are connected to the root node through several layers of threshold structures;

[0053] A node without subordinates is a leaf node and has a unique leaf node attribute value A. i ;

[0054] The node with subordinates is a threshold node, which has a logical attribute θ; the logical attribute θ controls the attribute value k of the threshold node θ ; If the logical attribute θ = or, then the threshold node attribute value k θ =1; if the logical attribute θ = and, then the threshold node attribute value k θ =n θ ={A θ}, where n θ is the set of attribute values ​​of its child nodes, A θ is its child node attribute;

[0055] The top node is the root node, which has the migration flag attribute U o ;

[0056] If the data requester wants to obtain the data of a leaf node, it needs to have the attribute value set by the node data owner and the root node migration flag attribute U o The attribute value corresponding to the migration state;

[0057] like Figure 2 As shown in the figure, based on the data that needs to be transmitted or migrated, the root node is the destination data storage end and owns all or core data. Other nodes can own part of the data with the authorization of the root node. The data in the lower-level nodes are obtained from the upper-level nodes. In other words, all data in any non-root node that stores part of the required data is owned by its upper-level node. This ensures that the user end of any bottom-level node can obtain all the data through layer-by-layer requests, such as Figure 2As shown, assuming that threshold node 3 stores data DATE, it is obtained from the upper-level node threshold node 1, and the data DATE in threshold node 1 is obtained from its upper-level node. Then leaf node C needs to obtain data DATE. Although it does not interact directly with threshold node 3, it can obtain corresponding data from threshold node 1, the upper-level node of threshold node 3. However, it still needs to pass the attribute verification of upper-level node threshold node 2 that does not store data DATE, while threshold node 1 only verifies the attributes of threshold node 1. If both pass, the corresponding encrypted data DATE is transferred to leaf node C through cloud migration.

[0058] The simple process is as follows. Assuming that the data request end needs the data of any leaf node, it is required to have the attribute value preset by the corresponding leaf node. For example, threshold node 2 has two subordinate nodes BC. Since its logical attribute value θ = and, assuming that the data request end wants to access the data in threshold node 2, the data request end must have all the attributes of its two subordinate nodes, that is, the attribute values ​​of leaf node B and leaf node C at the same time, and the root node migration flag attribute U o The data of threshold node 2 can only be obtained when the state is migratable; that is, the data request end needs to have the following attribute value combination: B+C;

[0059] Similarly, threshold node 3 has two subordinate nodes DE, whose logical attribute value θ=or. Assuming that the data request end wants to access the data in threshold node 3, the data request end must have at least one of the attributes of its two subordinate nodes, that is, the attribute value of leaf node D or leaf node E, and the root node migration flag attribute U o The data of threshold node 3 can only be obtained when the state is migratable; that is, the data request end needs to have the following attribute value combination: D or E;

[0060] Similarly, threshold node 1 has two subordinate nodes, threshold node 2 and threshold node 3, whose logical attribute value θ = and. Assuming that the data request end wants to access the data in threshold node 1, the data request end must have the attributes of threshold node 2 and threshold node 3 at the same time, that is, it must have the attributes of leaf node B and leaf node D at the same time, as well as the attribute value of leaf node D or leaf node E, and the root node migration flag attribute U o The data of threshold node 1 can only be obtained when the state is migratable; that is, the data request end needs to have the following attribute value combination: B+C+D or B+C+E;

[0061] A2. Configure system initial parameters

[0062] After building the basic system structure, it is necessary to determine the parameters or algorithms for data decryption and other processes during the actual execution process. This part of the work is completed by the credit end. The credit end refers to a specific entity that is trusted by the user end and provides encryption content such as decryption algorithms and verification rules to each user end. The credit end does not store and process data, but is only used to provide effective and secure algorithms, keys and other information.

[0063] In this application, the user end (including the data storage end and the data request end) first jointly negotiates to determine a specified migration flag attribute U o Provided to the credit end; migration flag attribute U o It is the key information used by the credit end to confirm the initiation and completion of the data migration and transmission task. o The secret key will be sent only when there is compliance.

[0064] In this application, verification is implemented based on the attributes of the node user. Therefore, the basic principle of bidirectional pairing is used to establish the basis of the decryption process. First, the credit end needs to generate a multi-order multiplication cyclic group G and G T , construct a bilinear pair e(G,G):G×G→G T ; Generate hash function H 1 ={0,1} * →G * and Generate random parameters α, β, Create the secret key MSK and execute the secret key parameter keyfor release process, where:

[0065] keyfor=p,G,G T ,g,e(G,G),H 1 ,H 2 ,U o ,e(g,g) α ,g β ,g γ ;

[0066] MSK=(g α ,β,γ);

[0067] where p is a multi-factorial cyclic group G and G T The order of; g is the generator of the cyclic group G; a cyclic group means that each generator in the group is a power of a fixed generator, for example G = {a, a 1 ,a 2 ,a 3 ...};

[0068] For a bilinear pair e(G,G):G×G→G T, the generator of the multi-factorial cyclic group G {g i},satisfy g a ,g b ∈{g i}.

[0069] A3 Generate Data Transfer Key

[0070] According to the attributes of the user end and its corresponding nodes in the data migration and transmission process, a node attribute parameter set S = {A i} and determine the attributes of the leaf nodes of each seat data request end; the credit end is the attribute A of each leaf node i Assigning random parameters and for a class with the attribute set User j A randomly generated unique certification mark Provide the private key After that, the user side calculates and publishes the user side User j The public key At the same time, calculate the user j The decryption key in Finally, the user j Private key Set j And the decryption key SK j Send securely to the user end;

[0071] To ensure confidentiality, the above key will be provided to the user through a secure method or channel. j ;

[0072] A4. Steps for data encryption storage

[0073] The data storage end selects a random symmetric encryption key κ∈G according to its own configuration T , use the symmetric encryption algorithm to encrypt the migration data Date and the symmetric key κ; assign the associated secret attribute s to the node θ based on the attribute access structure θ , secret attributes θ Based on its upper node, all lower nodes of node θ are obtained and shared; specifically:

[0074] The root node generates random secret numbers S', S", S”≠S”’; S” and S”’ are used to generate the migration flag attribute U o ; For any node θ, design k θ -1 degree polynomial f,

[0075] is the child node of node θ Assigning relatively unique index values Generate secret parameters for child nodes Get child nodes The ciphertext formula is in Refers to the child node Attribute value of

[0076] A5. Steps for verifying data migration messages

[0077] The data storage end uploads the encrypted data to the cloud service end, and then sends a migration message Tran = {User j ,name,U o ,dex,tag,sig}

[0078] Where name refers to the data file name, and dex refers to the lower-level child node ID;

[0079] tag=H 1 (name||U 0 ||dex);

[0080] The cloud server is based on the index value Generate verification information for dex nodes;

[0081] After receiving the migration message Tran, the credit end verifies the legitimacy of the user's identity by using the user's secret key parameter keyfor, that is, whether it satisfies e(tag,Oet j )=e(sig,g); if the verification is passed, the credit end calculates tag'=h 1 (name||U 0 ||dex) and compare it with tag to verify the migration message Tran. If the two are consistent, the verification is successful, and the corresponding message list is generated according to the migration control attribute of the migration message Tran;

[0082] A6. Steps to start data migration

[0083] When the migration specification of the data storage segment is reached, the credit end generates a migration token TranT i =H 1 (i) δ ; and send a migration request instruction TranR = (U j ,name,TranT i ,index); After receiving the data, the cloud server runs the multi-target tracking algorithm to obtain the data verification information and track the root node of the current data, and start data migration;

[0084] A7. Steps to decrypt data and obtain data content

[0085] Data request end j The retrieval system downloads the ciphertext data and calculates the ciphertext data according to its attribute set S j And user name and other information with decryption key SK j Run the decryption algorithm. The decryption process is based on constructing the attribute access structure from bottom to top, that is, from leaf nodes to root nodes. The specific steps are as follows:

[0086] When the data request end U j The attribute set S j Contains the attribute A of the leaf node θ i , then the decryption calculation formula can be expressed as:

[0087]

[0088] When the data request end U j The attribute set S j The attribute A that does not contain the leaf node θ i , then output JM θ =⊥; For the root node Root, if JM θ ≠⊥ and the migration message Tran passes the verification, then it passes Get the data in the ciphertext.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A cloud data encryption and decryption transmission system, It is characterized in that Including cloud service end, user end, and credit end; The cloud server is used to realize the online storage, transmission and deletion of ciphertext and other messages; the user end has different attributes according to its different identities in the data transmission process, including the data storage end and the data request end; The user end establishes an attribute access structure based on the tree structure, and the attribute access structure is used to hide the encryption key of the source data; The credit end is used to generate and store secret keys, encryption and decryption algorithms and provide them to the user end or cloud server upon request.

2. The cloud data encryption and decryption transmission system according to claim 1, It is characterized in that The attribute access structure includes a root node, a leaf node, and a threshold node; a leaf node is a subordinate node of a threshold node; a threshold node is connected to a root node through several layers of threshold structures; a node without a subordinate is a leaf node, and has a unique leaf node attribute value A i ; The node with subordinates is a threshold node, which has a logical attribute θ; the logical attribute θ controls the attribute value k of the threshold node θ ; If the logical attribute θ = or, then the threshold node attribute value k θ =1; if the logical attribute θ = and, then the threshold node attribute value k θ =n θ ={A θ }, where n θ is the set of attribute values ​​of its child nodes, A θ It is the attribute of its child node; the top node is the root node, which has the migration flag attribute U o If the data request end wants to obtain the data of a leaf node, it needs to have the attribute value set by the node data owner and the root node migration flag attribute U o The attribute value corresponding to the migration state.

3. The cloud data encryption and decryption transmission system according to claim 2, It is characterized in that The credit terminal is also used to generate multi-factorial cyclic groups G and G T , construct a bilinear pair e(G,G):G×G→G T ; For a bilinear pair e(G,G):G×G→G T , the generator of the multi-factorial cyclic group G {g i },satisfy 4. The cloud data encryption and decryption transmission system according to claim 1, It is characterized in that The migration flag attribute U o Determined by the user through consultation.

5. A data migration method based on the cloud data encryption and decryption transmission system in claim 1, It is characterized in that The steps include: A1. Steps to establish a user-side data system based on a tree structure A user-side attribute access structure is established based on a tree structure, including a root node, a leaf node, and a threshold node; the leaf node is a lower-level node of the threshold node, and the uppermost node is the root node; A2. Steps to configure system initial parameters Credit end specifies the migration flag attribute U o , generating multi-factorial cyclic groups G and G T , construct a bilinear pair e(G,G):G×G→G T ; Generate hash function H 1 ={0,1}*→G* and Generate random parameters Create the secret key MSK and execute the secret key parameter keyfor release process, where: keyfor=p,G,G T ,g,e(G,G),H 1 ,H 2 ,U o ,e(g,g) α ,g β ,g γ ; MSK=(g α ,b,c); where p is a multi-factorial cyclic group G and G T The order of ; g is the generator of the cyclic group G; A3. Steps to generate data transmission keys Based on the established tree structure, establish a node attribute parameter set S = {A i }, for each leaf node attribute A i Assigning random parameters For a property set User j Randomly generated certification mark For the user side User j Select Private Key Calculate and publish the user side User j The public key At the same time, calculate the user j The decryption key in User j Private key Set j And the decryption key SK j Send securely to the user end; A4. Steps for data encryption and storage The data storage end selects a random symmetric encryption key κ∈G according to its own configuration T , use the symmetric encryption algorithm to encrypt the migration data Date and the symmetric key κ; assign the associated secret attribute s to the node θ based on the attribute access structure θ , secret attributes θ Based on its upper node, it obtains and shares with all lower nodes of node θ; specifically: the root node generates a random secret number Where S” and S”’ are used to generate the migration flag attribute U o ; For any node θ, design k θ -1 degree polynomial f; child nodes of node θ Assigning relatively unique index values Generate secret parameters for child nodes Get child nodes The ciphertext formula is in Refers to the child node Attribute value of A5. Steps for verifying data migration messages The data storage end uploads the encrypted data to the cloud service end, and the data storage end sends a migration verification message Tran = {User j ,name,U o ,dex,tag,sig}; Where name refers to the data file name, and dex refers to the lower-level child node ID; tag=H 1 (name||U 0 ||dex); The cloud server is based on the index value Generate verification information for dex nodes; After receiving the migration message Tran, the credit end verifies the legitimacy of the user's identity by using the user's secret key parameter keyfor, that is, whether it satisfies e(tag,Oet j )=e(sig,g); if the verification is passed, the credit end calculates tag'=h 1 (name||U 0 ||dex) and compare it with tag to verify the migration message Tran. If the two are consistent, the verification is successful, and the corresponding message list is generated according to the migration control attribute of the migration message Tran; A6. Steps to start data migration When the migration request from the data requesting end arrives, the credit end generates a migration token TranT i =H 1 (i) δ ; and send a migration request instruction TranR = (U j ,name,TranT i ,index); After receiving the data, the cloud server runs the multi-target tracking algorithm to obtain the data verification information and track the root node of the current data, and start data migration; A7. Steps to decrypt data and obtain data content Data request end j The retrieval system downloads the ciphertext data and calculates the ciphertext data according to its attribute set S j And user name and other information with decryption key SK j Run the decryption algorithm. The decryption process is based on constructing the attribute access structure from bottom to top, that is, from leaf nodes to root nodes. The specific steps are as follows: When the data request end U j The attribute set S j Contains the attribute A of the leaf node θ i , then the decryption calculation formula can be expressed as: When the data request end U j The attribute set S j The attribute A that does not contain the leaf node θ i , then output JM θ =⊥; For the root node Root, if JM θ ≠⊥ and the migration message Tran passes the verification, then it passes Get the data in the ciphertext.

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