A Delegable Inner Product Function Encryption Method

Abstract

The present invention proposes a delegable inner product function encryption method, which consists of the following steps: system initialization phase, key generation phase, encryption phase, delegated key generation phase, and decryption phase. The method has the following characteristics: 1. The user's key is bound to his identity and a vector; 2. The user can directly delegate his decryption right to a trustee and set the validity period of the delegation; 3. The trustee can only decrypt the ciphertext within the delegation period; 4. The scheme does not require any agency to re-encrypt the data.

Description

Technical Field

[0001] The invention belongs to the field of computer security, and in particular relates to a delegable inner product function encryption method. Background Art

[0002] In order to protect the confidentiality of data, encryption schemes have been proposed. Existing encryption schemes can be divided into two categories: symmetric encryption and public key encryption. In symmetric encryption schemes, the same key is used for encryption and decryption operations. Unlike symmetric encryption, in public key encryption schemes, the public key is used by the user to encrypt messages, and the private key is used to decrypt messages. In particular, it is computationally infeasible to obtain the private key from the public key. Inner product function encryption is a special public key encryption scheme. In this scheme, the key and ciphertext are embedded in a vector respectively. A key holder can calculate the inner product of the vector embedded in the key and the vector embedded in the ciphertext without obtaining any other information about the plaintext. Since it supports calculations on ciphertext, inner product function encryption can be used in machine learning and data mining to protect the confidentiality of data and support analysis of plaintext.

[0003] The existing inner product function encryption mainly considers the security of the scheme. At present, inner product function encryption with chosen plaintext security and chosen ciphertext security has been proposed one after another. Inner product function encryption is used to securely calculate the distance between two vectors, the average value of elements contained in a vector, etc. Nevertheless, in existing related schemes, users can decrypt ciphertext with their keys, but they cannot transfer the decryption right to other users. However, in some special cases, users may not be able to decrypt by themselves. For example, users may not be able to access the Internet when they are on vacation or traveling. Therefore, users need to entrust others to perform decryption on their behalf.

[0004] In order to support the transfer of decryption rights, the present invention proposes a delegable inner product function encryption method. The method has the following characteristics. 1. The user's key is bound to his identity and a vector; 2. The user can directly delegate his decryption rights to a trustee and set the validity period of the delegation; 3. The trustee can only decrypt the ciphertext within the delegation period; 4. This scheme does not require any agency to re-encrypt the ciphertext. Summary of the invention

[0005] The present invention proposes a delegable inner product function encryption method, which allows a user to delegate his / her decryption right to a trustee, thereby improving the flexibility of the inner product function encryption scheme.

[0006] The present invention is achieved through the following technologies.

[0007] (1) System initialization phase: The central authority CA inputs a security parameter 1 k , output the system master key msk and system public parameters params, that is,

[0008] Setup(1 k )→(msk,params);

[0009] (2) Key generation phase: The central authority CA inputs public parameters params, master key msk, and user U’s identity information ID U and a vector Output a key Right now

[0010]

[0011] (3) Encryption phase: The encryptor inputs public parameters params and a validity period T E and a message Output ciphertext CT, that is

[0012]

[0013] (4) Delegated key generation phase: User U inputs public parameters params and key Trustee D's ID D and a delegation validity period T D , output a delegation key Right now

[0014]

[0015] (5) Decryption phase: This phase is divided into the user decryption phase and the agent decryption phase.

[0016] User decryption stage: User U inputs public parameters params and key And the ciphertext CT, output inner product Right now

[0017]

[0018] Trustee decryption phase: Trustee D inputs public parameters params and delegation key Entrustment validity period T D And the ciphertext CT, output inner product If and only if T E =T D ,Right now

[0019]

[0020] As a further improvement of the present invention, step (2) is characterized in that the user's key is bound to his / her identity to prevent key sharing;

[0021] As a further improvement of the present invention, in step (4), the user can entrust the decryption right to the trustee and set the validity period of the entrustment, thereby improving the flexibility of the inner product function encryption.

[0022] As a further improvement of the present invention, in step (5), within the validity period of the entrustment, the trustee can directly decrypt the ciphertext without any organization re-encrypting the ciphertext.

[0023] Compared with the existing inner product function encryption, the present invention has the following characteristics:

[0024] (1) The user key is bound to his / her identity to prevent key sharing and improve the security of the inner product function encryption scheme;

[0025] (2) The user can transfer the decryption right to the trustee and set the validity period of the entrustment, thus realizing the transfer and flexible revocation of the decryption right.

[0026] (3) The present invention does not require any other organization to re-encrypt the ciphertext. During the validity period of the entrustment, the entrustee can directly decrypt the ciphertext on behalf of the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0028] Figure 1 It is a process framework diagram of the present invention. DETAILED DESCRIPTION

[0029] According to the accompanying drawings, the specific implementation of the present invention is as follows.

[0030] The present invention consists of the following stages.

[0031] (1) System initialization phase: Assume that BG(1 k )→(e,p,G 1 ,G 2 ,G T ) is a bilinear group generation algorithm. The algorithm inputs the security parameter 1 k , output prime number p-order cyclic group G 1 ,G 2 ,G T , where e:G 1 ×G 2 →G T The central authority CA enters a security parameter 1 k , run BG(1 k )→(e,p,G 1 ,G 2 ,GT ). The central agency selects the generator g,g 0 ,g 1 ,g 2 ,g 3 ,g 4 ∈G 1 ,h∈G 2 and a hash function H:{0,1} * →Z p , where Z p is a cyclic group modulo p. The central agency randomly selects x 1 ,x 2, s 1 ,s 2 ,...,s n ∈Z p , then calculate

[0032]

[0033]

[0034] The system's master key is msk=(x 1 ,x 2, s 1 ,s 2 ,...,s n The common parameters of the system are params = (e, p, G 1 ,G 2 ,G T ,g,g 0 ,g 1 ,g 2 ,g 3 ,g 4 ,h,H,X 0 ,X 1 ,X 2 ,X 3 ,Y 1 ,Y 2 ,...,Y n ). Assume

[0035] (2) Key generation phase: The central institution is the identity ID U User U generates a vector The central authority first randomly selects r U ,w U ∈Z p , then calculate

[0036]

[0037] User User U About Vector The key is

[0038] (3) Encryption phase: Assume that the plaintext message is Valid for T E The encryptor first randomly selects r∈Z p , then calculate

[0039]

[0040]

[0041] The ciphertext is

[0042] (4) Delegated key generation phase: Assume that the key of user U is The identity of the trustee D is ID D The entrustment is valid for T D User U first randomly selects z D ∈Z p , then calculate

[0043]

[0044] The trusted key is

[0045] (5) Decryption phase: This phase consists of the user decryption phase and the trustee decryption phase.

[0046] User decryption phase: given ciphertext User U uses the key calculate

[0047]

[0048] Furthermore, user U calculates The discrete logarithm of e(g,h) gives Require Not too big.

[0049] Trustee decryption: Given ciphertext Trustee D uses the key calculate

[0050]

[0051] Furthermore, the trustee D calculates Regarding the discrete logarithm of e(g,h), we get Require Not too big.

[0052] The above content is only one embodiment of the present invention, and its description is detailed, but it cannot be used as a limitation on the scope of the invention patent. Under the premise of those skilled in the art without creative work, through deformation or minor improvements, they are also included in the patent protection scope of the present invention.

Claims

1. A delegable inner product function encryption method, characterized in that: It consists of the following steps: (1) System initialization phase: The central authority CA inputs a security parameter 1 k , output the system master key msk and system public parameters params, that is, Setup(1 k )→(msk,params); (2) Key generation phase: The central authority CA inputs public parameters params, master key msk, and user U’s identity information ID U and a vector Output a key Right now (3) Encryption phase: The encryptor inputs public parameters params and a validity period T E and a message Output ciphertext CT, that is (4) Delegated key generation phase: User U inputs public parameters params and key Trustee D's ID D and a delegation validity period T D , output a delegation key Right now (5) Decryption stage: This stage is divided into the user decryption stage and the agent decryption stage; System initialization phase: Assume BG(1 k )→(e,p,G1,G2,G T ) is a bilinear group generation algorithm; the algorithm inputs the security parameter 1 k , output prime p-order cyclic group G1, G2, G T , where e: G1×G2→G T ; The central authority CA enters a security parameter 1 k , run BG(1 k )→(e,p,G1,G2,G T ); The central agency selects generators g, g0, g1, g2, g3, g4∈G1, h∈G2 and a hash function H: {0, 1} * →Z p , where Z p is a cyclic group modulo p; the central agency randomly selects x1, x2, s1, s2, ..., s n ∈Z p , then calculate The master key of the system is msk=(x1, x2, s1, s2, ..., s n ); The common parameters of the system are params = (e, p, G1, G2, G T ,g,g0,g1,g2,g3,g4,h,H,X0,X1,X2,X3,Y1,Y2,...,Y n ); Assumptions Key generation phase: the central agency is the identity ID U User U generates a vector The central agency first randomly selects rU, w U ∈Z p , then calculate User User U About Vector The key is Encryption phase: Assume the plaintext message is Valid for T E ; The encryptor first randomly selects r∈Z p , then calculate The ciphertext is Delegation key generation phase: Assume that user U's key is The identity of the trustee D is ID D The entrustment is valid for T D ; User U first randomly selects z D ∈Z p , then calculate The trusted key is Decryption phase: This phase consists of the user decryption phase and the trustee decryption phase; User decryption phase: given ciphertext User U uses the key calculate User U calculates The discrete logarithm of e(g, h) gives Trustee decryption: Given ciphertext Trustee D uses the key calculate Trustee D calculates Regarding the discrete logarithm of e(g, h), we get 2. A delegable inner product function encryption method according to claim 1, characterized in that: The step (2) is specifically embodied in: binding the key to the user's identity.

3. A delegable inner product function encryption method according to claim 1, characterized in that: The step (4) is specifically embodied in that: the user can entrust his key to the trustee and the trustee can only decrypt on behalf of the user within the validity period of the entrustment.

4. The entrustable inner product function encryption method according to claim 1, characterized in that: The user decryption stage and the agent decryption stage in step (5) are respectively as follows: User decryption stage: User U inputs public parameters params and key And the ciphertext CT, output inner product Right now Trustee decryption phase: Trustee D inputs public parameters params and delegation key Entrustment validity period T D And the ciphertext CT, output inner product If and only if T E =T D ,Right now 5. A delegable inner product function encryption method according to claim 4, characterized in that: The step (5) is specifically embodied in that: within the validity period of the entrustment, the entrustee can directly decrypt the ciphertext without any organization re-encrypting the ciphertext.

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