KR101240247B1 - Proxy re-encryption Method using two secret key, Method for decrypting of Proxy re-encryption message - Google Patents

Abstract

The present invention relates to a proxy re-encryption method, comprising: generating two secret keys using a public parameter, a master secret key, and a delegate personal identification information, and encrypting a message by using the public parameter and the delegate personal identification information. Generating a re-encryption key using the public parameter, the two secret keys, the delegate personal identification information, and the delegate personal identification information, and re-encrypting the encrypted message using the re-encryption key. It is characterized in that it comprises a step, by using the two secret keys are safe from collusion attacks of proxies and agents.

Description

Proxy re-encryption method using two secret key, method for decrypting of proxy re-encryption message}

The present invention relates to a proxy re-encryption method and a proxy re-encryption message decryption method, and more particularly, to secure an ID-based proxy re-encryption method and a message encrypted by the method by using two secret keys. It relates to a proxy re-encryption message decoding method, and a recording medium.

The ID-based proxy re-encryption scheme allows a proxy server to decrypt ciphertext encrypted with the delegate's public identity with the proxy's secret key. A technique for converting ciphertext. In an ID-based re-encryption system, a delegate can temporarily distribute the decryption right of his / her ciphertext to the proxy through a proxy without exposing his private key. This re-encryption technique can be used as a source technology for many applications such as digital rights management, email delivery systems, and access control in distributed data storage. As an example, consider an access control system for distributed network repositories among various applications. In such an access control system, the delegator encrypts the content with its public ID as a content provider and stores it in a network repository. The proxy, when allowing the proxy's access to its own content as an access controller for the system, It converts to a ciphertext that can be decrypted with the secret key of.

The proxy re-encryption technique maintains confidentiality by providing a re-encryption method of a cipher text by a re-encryption key and a multi-distribution method by a multi proxy when sharing information of medical data in a prior patent domestic patent (KR 10-2010-0008711). It is used in a multi-proxy re-encryption-based medical data sharing method and apparatus, and US Patent Publication (US 2008-0059787) generates a key pair including a public key and a secret key and generates a re-encryption key that changes encryption. It is used to encrypt a message. In addition, the proxy re-encryption technique is used in a variety of prior documents, such as domestic registered patents (KR 10-2005-0044242, KR 10-2003-0045217).

Basically, when the proxy performs the re-encryption process of converting the ciphertext, the proxy must not know the secret key of the delegate and the delegate, and alone cannot know the plaintext information about the ciphertext.

Additionally, collusion between proxies and delegates or proxies and agents should not reveal system security vulnerabilities. In the structure of the ID-based re-encryption scheme, collusion between the proxy and the delegate can always decrypt (within certain given conditions) a ciphertext (or part of a ciphertext) encrypted with the delegate's identity. However, proxies and proxy collusion may expose useful information about the delegate's private key, which is a serious security threat. This is because the user's private key is used to perform important and user-sensitive security tasks in various forms.

However, previous studies have a weak structure in which the proxy's secret key is exposed through the public attack of the proxy and the proxy.

The first problem to be solved by the present invention is to provide a proxy re-encryption method that is safe against collusion attack by using two secret keys.

The second problem to be solved by the present invention is to provide a proxy re-encryption message decryption method for decrypting a message encrypted by a proxy re-encryption method that is safe for collusion attack using two secret keys.

Further, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above method on a computer.

In order to achieve the first task, the present invention comprises the steps of generating two secret keys using the public parameter, the master secret key, and the delegate personal identification information, the message using the public parameter and the delegate personal identification information; Encrypting, generating a re-encryption key using the public parameter, the two secret keys, the delegate personal identification information, and the delegate personal identification information, and regenerating the encrypted message using the re-encryption key. It provides a proxy re-encryption method comprising the step of encrypting.

According to an embodiment of the present disclosure, the generating of the re-encryption key may include calculating a first hash value from the delegate personal identification information using a first hash function, and using the first linear function. Calculating each operation value from a hash value and each of the secret keys, and generating the re-encryption key from a predetermined random number and the ratio of the two secret keys, wherein the ratio of the two secret keys is The proxy re-encryption method may be calculated from the operation value and the two secret keys.

The present invention includes the steps of receiving a re-encrypted message, and decrypting the re-encrypted message using a public parameter and a delegate secret key, to achieve the second object, the re-encrypted message Generate two secret keys using the public parameter, the master secret key, and the delegate personal identification information, encrypt the message using the public parameter and the delegate personal identification information, and use the public parameters, the two secrets. A proxy re-encryption message decryption method is generated by generating a re-encryption key using a key, the delegate personal identification information, and a delegate personal identification information, and re-encrypting the encrypted message using the re-encryption key. To provide.

In order to solve the above other technical problem, the present invention provides a computer-readable recording medium recording a program for executing the proxy re-encryption method and the proxy re-encryption message decoding method in a computer.

According to the present invention, by using two secret keys, it is safe to attack the proxy and proxy. Also, the delegate's private key is not exposed.

1 is a block diagram illustrating a proxy re-encryption apparatus according to an embodiment of the present invention.
2 is a diagram illustrating parameters and keys used during re-encryption of a message by a proxy re-encryption method according to another embodiment of the present invention.
3 is a flowchart of a proxy re-encryption method according to an embodiment of the present invention.
4 is a flowchart of a method for generating a re-encryption key according to another embodiment of the present invention.
5 is a flowchart of a method for re-encrypting an encrypted message according to another embodiment of the present invention.
6 is a flowchart of a method for decrypting a proxy re-encryption message according to an embodiment of the present invention.

Prior to the description of the specific contents of the present invention, for the convenience of understanding, the outline of the solution of the problem to be solved by the present invention or the core of the technical idea will be presented first.

In the proxy re-encryption method according to an embodiment of the present invention, generating two secret keys using a public parameter, a master secret key, and a delegator personal identification information, and using the public parameter and the delegator personal identification information. Encrypting, generating a re-encryption key using the public parameter, the two secret keys, the delegate personal identification information, and the delegate personal identification information, and using the re-encryption key to encrypt the encrypted message. Re-encrypting.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, these examples are intended to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited thereby.

The configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings based on the preferred embodiment of the present invention, the same in the reference numerals to the components of the drawings The same reference numerals are given to the components even though they are on different drawings, and it is to be noted that in the description of the drawings, components of other drawings may be cited if necessary. In addition, in describing the operation principle of the preferred embodiment of the present invention in detail, when it is determined that the detailed description of the known function or configuration and other matters related to the present invention may unnecessarily obscure the subject matter of the present invention, The detailed description is omitted.

1 is a block diagram illustrating a proxy re-encryption apparatus according to an embodiment of the present invention.

The delegate 110 distributes the message encrypted with the private key to the delegate 130 using the proxy re-encryption device 120.

The proxy re-encryption apparatus 120 re-encrypts the encrypted message using the re-encryption key. The re-encryption key is generated using a public parameter, two secret keys, delegate personal identification information received from the delegate 110, and delegate personal identification information input from the delegate 130. The re-encryption key calculates a hash value from the delegate personal identification information using a hash function, and calculates respective operation values from the hash value and each secret key by using an overlap function, thereby providing a predetermined random number and the A ratio of two secret keys is generated, and a ratio of the two secret keys is calculated from the operation value and the two secret keys. A detailed description of the apparatus corresponds to the detailed description of FIG. 2, which will be described in detail in the detailed description of FIG. 2.

The delegate 130 checks the message by the proxy re-encryption device 120 decrypting the re-encrypted message with its private key. The delegate 130 can decrypt the re-encrypted message only if the delegate 110 grants access to the re-encrypted message.

2 is a diagram illustrating parameters and keys used during re-encryption of a message by a proxy re-encryption method according to another embodiment of the present invention.

The secret key 250 is generated using the master secret key 210, the public parameter 220, and the delegate personal identification information 230. The encrypted message 280 is generated by encrypting the message 270 using the public parameter 220 and the delegate personal identification information 230. The re-encryption key 260 is generated using the public parameter 220, the delegate personal identification information 230, the delegate personal identification information 240, and the secret key 250. The re-encryption message 280 is re-encrypted using the re-encryption key 260 to generate the re-encrypted message 290.

In the proxy re-encryption method using the parameters and keys according to the embodiment of the present invention, since the re-encryption key is generated using the ratio of two secret keys, the secret keys are not exposed even though the ratio of the secret keys is exposed. It is safe from collusion attacks by malicious proxies and agents. Looking at the proxy re-encryption method using the parameters and keys according to an embodiment of the present invention as a whole.

First, set up the public parameters and master secret key (Setup (1 ^k ) step)

More specifically, it creates cyclic groups (G ₁ , G ₂ , e) associated with the linear function. G1 and G2 have a prime q as an upper order, and e: G ₁ × G ₁ → G ₂ is an admissible bilinear map. The overlap function is the presence of P, Q∈G _x that satisfies the overlapping e (P, Q) ≠ 1 satisfying e (P ^a , Q ^b ) = e (P, Q) ^ab , and all P, This function satisfies the efficiency of computing e (P, Q) for Q∈G _x . The random generator g and a cryptographic hash function in _{G 1 H i: {0,1}} * → G 1 * (i = 1,2,3), H 4: G 2 * × {0,1} n → Z _q ^* , H ₅ : G ₂ → {0,1} Select ⁿ . An arbitrary random number α, β∈Z _q ^* is selected and w = g ^α-β is calculated. The public parameter (PP) and the master secret key (Master Key, MK) are set as in Equation 1 below.

[Equation 1]

PP = (G ₁ , G ₂ , e, q, g, w = g ^α-β , H ₁ , H ₂ , H ₃ , H ₄ , H ₅ )

MK = α, β

Second, create two private keys for the delegate (Extract (MK, PP, ID) step).

More specifically, the master secret key MK, the public parameter PP, and the personal identification information ID 별 {0,1} ^* are input. Using the personal identification information, two secret keys SK _ID are generated as in Equation 2 below.

&Quot; (2) "

SK _ID = (H ₁ (ID) ^α , H ₂ (ID) ^β )

Third, encrypt the message (Encryption (M, PP, ID) step)

H₅(σ))을 산출한다. 상기 암호문 c'을 이용하여 h = H₃(ID∥c')∈G₁를 생성하고 S = h^r을 산출한다. 상기 S와 암호문 c'를 이용하여 메시지(M)를 암호화한 암호문 C_ID를 다음 수학식 3과 같이 생성한다.More specifically, the message M, the public parameter PP, and the delegator's personal identification information ID are received. Choose an arbitrary σ∈G ₂ and calculate r = H ₄ (σ, M). Next, ciphertext c '= (A, B, C) = (g ^r , σe (w, H ₁ (ID) ^r ), M

Calculate H ₅ (σ)). The ciphertext c 'is used to generate h = H ₃ (ID | c') 생성 G ₁ and calculate S = h ^r . A ciphertext C _ID that encrypts the message M using S and the ciphertext c 'is generated as in Equation 3 below.

&Quot; (3) "

C _ID = (S, A, B, C)

Fourth, generate a re-encryption key (steps RKGen (PP, SK _{ID1 ,} ID ₁ , ID _{2 )} ).

More particularly, the public parameters (PP), authorized agent receives the personal identification information (ID _1), delegate personal identification information (ID _2), secret key (SK _ID1). Select any random number N∈ {0,1 ⁿ } and K ₁ = e (H ₁ (ID ₁ ) ^α , H ₁ (ID ₂ )), K ₂ = e (H ₁ (ID ₁ ) ^β , H ₁ (ID ₂ )) is calculated. The re-encryption key RK _{ID1 → ID2} is generated using the random number, secret key, K ₁ , and K ₂ as shown in Equation 4 below.

&Quot; (4) "

Fifth, re-encrypt the encrypted message (Step Re-Encryption (PP, C _ID1 , RK _{ID1 → ID2} )).

)를 입력받는다. 우선, 상기 암호화된 메시지가 상기 암호화방법에 의해 암호화된 메시지인지 겹선형 함수를 이용하여 검증한다. h= H₂(ID∥(A,B,C))를 생성하고 e(g,S)=e(h,A)인지 검증한다. 상기 검증결과, 상기 식을 만족하는 경우에만 재암호화과정을 수행한다. 임의의 t∈Z_q ^*를 선택하고 B'= B·e(g^t,S)·e(A,RK_{ID1 → ID2}·h^t)^{- 1}를 산출하고, 암호화된 메시지를 재암호화한 암호문 C_ID2 를 다음 수학식 5와 같이 생성한다.More specifically, public parameter PP, encrypted message C _ID1 = (S, A, B, C)), re-encryption key (

) Is inputted. First, it is verified using an overlap function that the encrypted message is a message encrypted by the encryption method. Generate h = H ₂ (ID∥ (A, B, C)) and verify that e (g, S) = e (h, A). As a result of the verification, the re-encryption process is performed only when the equation is satisfied. Select any t∈Z _q ^*, and B '= B · e (g t, S) · e (A, RK ID1 → ID2 · h t) - 1 calculated, and a re-encrypting the encrypted cipher text message C _ID2 is generated as in Equation 5 below.

[Equation 5]

C _ID2 = (A, B ', C, ID ₁ , N)

Finally, the delegate decrypts the encrypted message. (Decryption (PP, C _ID , SK _ID ) step)

More specifically, the public parameter PP, the cipher text C _ID , and the secret key SK _ID are received. Depending on whether the ciphertext is encrypted or re-encrypted, there are two ways to decrypt it.

H₅(σ')을 산출하여 메시지를 복호화하고, r'=H₄(σ',M')을 생성한다. S=h^r'와 A=g^r'의 등호가 성립하는지 확인하여, 등호가 성립하는 경우에만 M'를 반환한다.The process of decrypting the ciphertext C _ID = (S, A, B, C) encrypted by the Encryption (M, PP, ID) step (Level 1) is first performed with h = H ₂ (ID∥). (A, B, C)) is calculated. Next, select any t∈Z _q ^*, and σ '= B · e (A , H 1 (ID) α · H 1 (ID) -β h t) · e (g t, S) - calculating a ^first do. M '= C using the above σ'

Calculate H ₅ (σ ′) to decode the message and generate r ′ = H ₄ (σ ′, M ′). Checks if the equal sign of S = h ^{r '} and A = g ^r' is true, and returns M 'only if the equal sign is true.

H₅(σ')을 산출하여 메시지를 복호화하고, r'=H₄(σ',M')을 생성한다. A=g^r'의 등호가 성립하는지 확인하여, 등호가 성립하는 경우에만 M'를 반환한다.Decrypting the ciphertext C _ID = (A, B, C, ID _src , N) re-encrypted by the Re-Encryption (PP, C _ID1 , RK _{ID1 → ID2} ) step (Level-2) First calculates K = e (H ₁ (ID _src ), SK _ID ), and calculates σ '= B e (A, H ₂ (K ∥ ID _src ∥ ID ∥ N).

Calculate H ₅ (σ ′) to decode the message and generate r ′ = H ₄ (σ ′, M ′). Checks if the equal sign of A = g ^{r '} is true and returns M' only if the equal sign is true.

As described in step 6 above, re-encrypting a message using two secret keys may be safe for collusion attacks of proxies and agents. Malicious proxies and conspirators use the re-encryption key (RK _{ID1 → ID2} ) and the delegate's secret key (H ₁ (ID ₂ ) ^α , H ₂ (ID ₂ ) ^β ) to K ₁ = e (H ₁ (ID ₁₎ ), H ₁ (ID ₂ ) ^α ) = e (H ₁ (ID ₁ ) ^α , H ₁ (ID ₂ )), and K ₂ = e (H ₁ (ID ₁ ), H ₁ (ID ₂ ) ^β ) = e (H ₁ (ID ₁ ) ^β , H ₁ (ID ₂ )) can be calculated. ID ₁ , ID _2, the N-environment all the published information, it is possible to calculate the _{P 1 = H 2 (K 1} ∥ID 1 ∥ID 2 ∥N), P 2 = H 2 (K 2 ∥ID 1 ∥ID 2 ∥N) have. By using the calculated values, it is possible to know the private key of the delegate as shown in Equation 6.

&Quot; (6) "

As in the ^{_{H 1 (ID 1) α /}} H 1 (ID 1) from ^β H ₁ (ID ₁₎ can be known only ^α and H ₁ (ID ₁₎ ^β ratio ^{_{of, H 1 (ID 1) α}} , H _{Since 1} (ID ₁ ) ^β is unknown, the private key of the delegate is not exposed.

On the other hand, when re-encrypting using one secret key rather than two secret keys, the delegate's private key may be exposed. When two secret keys are not used, the public parameter PP and the master secret key MK are different from Equation 1 as shown in Equation 7 below.

[Equation 7]

PP = (G ₁ , G ₂ , e, q, g, g ^s , H ₁ , H ₂ , H ₃ , H ₄ , H ₅ )

MK = s

In addition, the secret key SK _ID is different from Equation 2 as shown in Equation 8 below.

[Equation 8]

SK _ID = H ₁ (ID) ^α

Since only one secret key (SK _ID ) is used as described above, the re-encryption key is different from the case of using two secret keys. That is, the re-encryption key is different from Equation 4 as shown in Equation 9 below.

&Quot; (9) "

를 알 수 있으며, 상기 N은 {0,1}^n(k)에서 임의로 선택한 수이고 SK_ID1=H₁(ID₁)^α, K=e(H₁(ID₁),H₁(ID₂))^α이다. 프락시와 대리자는 우선 SK_ID2를 이용하여 K=e(H₁(ID₁),SK_ID2)=e(H₁(ID₁),H₁(ID₂))^α를 산출할 수 있다. 등록된 재암호화키 RK_{ID1 → ID2}와 상기 산출한 K를 이용하여 다음 수학식 10과 같이 위임자의 비밀키(SK_ID1)를 산출할 수 있다.In the re-encryption method using one of the secret keys (SK _ID ), the secret key of the delegator may be exposed by the collusion attack of the malicious proxy and the delegate. Proxies re-encrypt

Where N is a number selected randomly from {0,1} ^{n (k)} and SK _ID1 = H ₁ (ID ₁ ) ^α , K = e (H ₁ (ID ₁ ), H ₁ (ID ₂ ) ) ^α . Proxy and delegate may first use the SK _ID2 to calculate the _{K = e (H 1 (ID} 1), SK ID2) = e (H 1 (ID 1), H 1 (ID 2)) α. Using the registered re-encryption key RK _{ID1 → ID2} and the calculated K, the secret key SK _ID1 of the delegate can be calculated as shown in Equation 10 below.

&Quot; (10) "

3 is a flowchart of a proxy re-encryption method according to an embodiment of the present invention.

In step 310, two secret keys are generated by using the public parameter, the master secret key, and the delegate personal identification information.

More specifically, two secret keys are generated using the public parameters used for encryption and re-encryption, the master secret key required to generate the secret key, and the personal identification information of the delegate. Generate two secret keys to protect against collusion attacks by malicious proxies and agents. The detailed description of this step corresponds to the Extract (MK, PP, ID) step, and replaces the detailed description of the Extract (MK, PP, ID) step. The detailed description of the setting of the public parameter and the master secret key corresponds to the step of Setup ( ^1k ).

The two secret keys are generated by calculating a second hash value from the personal identification information of the delegate using a first hash function and exponentially multiplying the second hash value with two master secret keys.

More specifically, using the first hash function H _i : {0,1} ^* → G ₁ ^* (i = 1,2,3), the second hash value H ₁ (ID ₁ ) is obtained from the delegator's personal identification information. Calculate. Two secret keys SK _ID by exponentiating the second hash value H ₁ (ID ₁ ) with two master secret keys MK = α, β = (H ₁ (ID) ^α , H ₂ (ID) ^β ).

Step 320 is encrypting a message using the public parameter and the delegate personal identification information.

More specifically, the message is encrypted using the delegator's personal identification code. When encrypting a message, the public parameter set in the Setup (1 ^k ) step is used. The detailed description of this step corresponds to the Encryption (M, PP, ID) step, and replaces the detailed description of the Encryption (M, PP, ID) step.

In step 330, a re-encryption key is generated using the public parameter, the two secret keys, the delegate personal identification information, and the delegate personal identification information.

More specifically, a re-encryption key is generated using the public parameter, the delegate personal identification information, the delegate personal identification information, and the two secret keys generated in step 310. This step will be described in detail with reference to FIG. 4.

Step 340 is to re-encrypt the encrypted message using the re-encryption key.

More specifically, in step 320, the encrypted message is re-encrypted using the re-encryption key generated in step 330. Details of this step are described in Re-Encryption (PP, C _ID1 , RK _{ID1 → ID2).} Re-Encryption (PP, C _ID1 , RK _{ID1 → ID2)} Replace with a detailed description of the step.

The proxy re-encryption method according to an embodiment of the present invention may be implemented through a processor capable of processing a series of operations and a memory required for such an operation. A controller may be utilized that can appropriately control data processing between spaces. Such a processor, a storage space and a controller may be appropriately selected by those skilled in the art in consideration of the utilization environment or operating environment of the technical field to which the present invention belongs. Further, this control process may also utilize additional software code for controlling the hardware illustrated above.

4 is a flowchart of a method for generating a re-encryption key according to another embodiment of the present invention.

In operation 410, a first hash value is calculated from the delegate personal identification information by using a first hash function.

More specifically, the first hash value is calculated by inputting the delegate personal identification information into the first hash function. The first hash function may be H _i : {0,1} ^* → G ₁ ^* (i = 1,2,3). The hash value H ₁ (ID ₂ ) is calculated using the first hash function.

In operation 420, an operation value is calculated from the first hash value and the respective secret key using an overlap function.

More specifically, each operation value is calculated from the first hash value calculated in step 410 and each secret key generated in step 310. Each secret key is (H ₁ (ID) ^α , H ₂ (ID) ^β ), and the calculated value for H ₁ (ID) ^α K ₁ = e (H ₁ (ID ₁ ) ^α , H ₁ (ID ₂ ) ) and H ₂ (ID) value calculated for the ^{_{β K 2 = e (H 1}} (ID 1) β, H 1 (ID 2)) to be calculated.

In step 430, the re-encryption key is generated from a ratio of a predetermined random number and the two secret keys.

를 생성한다.More specifically, the re-encryption key is generated from a ratio of one particular random number and two secret keys generated in step 310. The ratio of the two secret keys is calculated from the operation value calculated in step 420 and the two secret keys. The random number may be N∈ {0,1 ⁿ }. Re-encryption key using the random number, the calculated values K ₁ and K ₂ , two secret keys

.

5 is a flowchart of a method for re-encrypting an encrypted message according to another embodiment of the present invention.

Step 510 is a step of calculating a third hash value from the personal identification information and the encrypted message of the delegate using a second hash function.

H₅(σ))와 위임자 개인식별정보로부터 h= H₂(ID∥(A,B,C))를 산출한다.More specifically, the third hash value is calculated by inputting the delegator's personal identification information and the encrypted message to the second hash function. Second hash function H _i : {0,1} ^* → Message encrypted using G ₁ ^* (i = 1,2,3) c '= (A, B, C) = (g ^r , σ · e (w, H ₁ (ID) ^r ), M

Calculate h = H ₂ (ID∥ (A, B, C)) from H ₅ (σ)) and delegate personal identification information.

In operation 520, the third hash value is used to determine whether the encrypted message satisfies the definition of the parallel function.

More specifically, it is determined whether the encrypted message satisfies the definition of the parallel function using the third hash value calculated in step 510. The third hash value h = H ₂ (ID < RTI ID = 0.0 > (A, B, C)) < / RTI >

In operation 530, when the encrypted message satisfies the definition of the double line function, the encrypted message is re-encrypted using the public parameter and the re-encryption key.

More specifically, if it is determined in step 520 that the definition of the double line function is satisfied, it is a step of re-encrypting the encrypted message using the public parameter, the encrypted message in step 320, and the re-encryption key generated in step 330. . Verify that e (g, S) = e (h, A) and perform re-encryption only if the above equation is satisfied. Select any t∈Z _q ^*, and B '= B · e (g t, S) · e (A, RK ID1 → ID2 · h t) - 1 calculated, and a re-encrypting the encrypted cipher text message C _{Create ID2} = (A, B ', C, ID ₁ , N).

6 is a flowchart of a method for decrypting a proxy re-encryption message according to an embodiment of the present invention.

Step 610 is a step of receiving a re-encrypted message.

More specifically, it receives a proxy re-encrypted message. The re-encrypted message generates two secret keys using the public parameter, the master secret key, and the delegate personal identification information, encrypts the message using the public parameter and the delegate personal identification information, and uses the public parameter. And a re-encryption key using the two secret keys, the delegate personal identification information, and the delegate personal identification information, and the re-encryption of the encrypted message using the re-encryption key. The re-encrypted message may be generated by the method of FIGS. 3 to 5. The detailed description of the re-encrypted message corresponds to the detailed description of FIGS. 3 to 5, and is replaced with the detailed description of FIGS. 3 to 5.

Step 620 is to decrypt the re-encrypted message using a public parameter and a delegate secret key.

More specifically, it is a step of decrypting the re-encrypted message using a secret key generated using the public parameter and the personal identification information of the delegate. Details of this step takes the place of the detailed description of the bar, the Decryption (PP, C _ID, SK _ID) phase corresponding to the phase Decryption (PP, C _{ID, ID} SK).

Embodiments of the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

110: delegate
120: proxy re-encryption device
210: master secret key
220: public parameter
230: delegator personally identifiable information
240: delegate personally identifiable information
250: secret key
260: re-encryption key
270: Message
280: Encrypted message
290: Re-encrypted message

Claims (9)

Generating two secret keys using the public parameters, the master secret key, and the delegate personal identification information;
Encrypting a message using the public parameter and the delegate personal identification information;
Generating a re-encryption key using the public parameter, the two secret keys, the delegate personal identification information, and the delegate personal identification information; And
Re-encrypting the encrypted message using the re-encryption key,
Generating the re-encryption key,
Calculating a first hash value from the delegate personal identification information by using a first hash function;
Calculating each operation value from each of the first hash value and the two secret keys using an overlap function; And
Generating the re-encryption key from a ratio of a predetermined random number and the two secret keys,
And the ratio of the two secret keys is calculated from the operation value and the two secret keys. delete The method of claim 1,
The two secret keys,
And generating a second hash value from the personal identification information of the delegate using a first hash function and exponentially multiplying the second hash value with two master secret keys. The method of claim 1,
The re-encryption step,
Calculating a third hash value from the delegate's personal identification information and the encrypted message using a second hash function;
Determining whether the encrypted message satisfies the definition of an overlapping function using the third hash value; And
And re-encrypting the encrypted message using the public parameter and the re-encryption key when the encrypted message satisfies the definition of an overlapping function. Receiving a re-encrypted message; And
Decrypting the re-encrypted message using a public parameter and a delegate private key,
The re-encrypted message,
Two secret keys are generated using the public parameter, the master secret key, and the delegate personal identification information, the message is encrypted using the public parameter and the delegate personal identification information, and the public parameters, the two secret keys are used. Generating a re-encryption key using the delegate personal identification information and the delegate personal identification information, and re-encrypting the encrypted message using the re-encryption key,
The re-encryption key,
A first hash value is calculated from the delegate personal identification information by using a first hash function, and each operation value is calculated from each of the first hash value and the two secret keys by using an overlap function, and a predetermined value is calculated. Is generated from the ratio of the random number and the two secret keys,
And a ratio of the two secret keys is calculated from the operation value and the two secret keys. delete The method of claim 5, wherein
The two secret keys,
And generating a second hash value from the personal identification information of the delegate using a first hash function and exponentially multiplying the second hash value with two master secret keys. The method of claim 5, wherein
The re-encrypted message,
Calculating a third hash value from the personal identification information and the encrypted message of the delegate using a second hash function, and determining whether the encrypted message satisfies the definition of the parallel function using the third hash value, If the encrypted message satisfies the definition of the double line function, the encrypted message is generated by re-encrypting the encrypted message using the public parameter and the re-encryption key. . A non-transitory computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1, 3 to 5, or 7 to 8.

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