阅读说明：本技术 重加密密钥生成装置、重加密装置、重加密密文解密装置以及密码系统 (Re-encryption key generation device, re-encryption device, re-encrypted ciphertext decryption device and encryption system ) 是由 小关义博 川合丰 于 2017-06-09 设计创作，主要内容包括：密钥生成装置(10)生成解密密钥(dk<Sub>x</Sub>),该解密密钥(dk<Sub>x</Sub>)具有：带标签解密密钥和设定了密钥属性(x)的解密密钥(adk<Sub>x</Sub>),其中,所述带标签解密密钥包含设定了密钥属性(x)的解密密钥(tdk<Sub>x</Sub>)以及为了利用解密密钥(tdk<Sub>x</Sub>)对密文进行解密所需的标签(tg<Sub>φ</Sub>)。加密装置(20)生成设定有与密钥属性(x)对应的密文属性(y)并能够利用带标签解密密钥进行解密的原始密文(oct<Sub>y</Sub>)。重加密密钥生成装置(40)通过基于属性的加密方式使用密文属性(y’)对解密密钥(tdk<Sub>x</Sub>)进行加密,生成作为用于生成重加密密文(rct<Sub>y’</Sub>)的密钥的重加密密钥(rk<Sub>x,y’</Sub>),所述重加密密文(rct<Sub>y’</Sub>)能够利用设定了与密文属性(y’)对应的密钥属性(x’)的解密密钥(adk<Sub>x’</Sub>)来进行解密。(A key generation device (10) generates a decryption key (dk) x ) The decryption key (dk) x ) Comprising: a labeled decryption key and a decryption key (adk) with a key attribute (x) set x ) Wherein the tagged decryption key comprises a decryption key (tdk) with a key attribute (x) set thereto x ) And in order to use the decryption key (tdk) x ) The label (tg) required to decrypt the ciphertext φ ). The encryption device (20) generates an original ciphertext (oct) that has a ciphertext attribute (y) corresponding to the key attribute (x) set therein and that can be decrypted using the tagged decryption key y ). A re-encryption key generation device (40) uses the ciphertext attribute (y') to encrypt the decryption key (tdk) by an attribute-based encryption method x ) Is encrypted and generated as a key for generating a re-encrypted ciphertext (rc)t y’ ) Re-encryption key (rk) of the key of (2) x，y’ ) The re-encrypted ciphertext (rct) y’ ) The decryption key (adk) in which the key attribute (x ') corresponding to the ciphertext attribute (y') is set can be used x' ) To perform decryption.)

1. A re-encryption key generation device, comprising:

a randomizer for decrypting the decryption key tdk with the key attribute x_xAnd in order to use said decryption key tdk_xTag tg for use in decrypting ciphertext_φSetting a random number to generate a decryption key tdk_xΛ and label tg_φ＾；

An encryption key generation unit that uses a ciphertext attribute y' to encrypt the decryption key tdk generated by the randomization unit in an attribute-based encryption method_xEncrypt for ^ to generate encrypted key act_y’(ii) a And

a re-encryption key output unit that outputs an encryption key act including the encryption key generated by the encryption key generation unit_y’And the tag tg generated by the randomizing part_φLambda re-encryption key rk_x，y’。

2. The re-encryption key generation apparatus according to claim 1,

the re-encryption key rk_x，y’Is used for generating an original ciphertext oct based on a ciphertext attribute y corresponding to the key attribute x_yGenerating a re-encrypted ciphertext rct_y’The re-encrypted ciphertext rct_y’The decryption key adk with the key attribute x 'corresponding to the ciphertext attribute y' set therein can be used_x’Decryption is performed.

3. The re-encryption key generation apparatus according to claim 1 or 2,

the randomizer generates a decryption key tdk as shown in equation 1_xA and tag tg_φ^，

The encryption key generation unit generates an encryption key act as shown in equation 2_y'

[ formula 1]

Wherein

s₀＝s₁+s₂

[ formula 2]

act_y′＝((y′，c₃,c_T)

Wherein

4. A re-encryption device, comprising:

a ciphertext acquisition unit for acquiring an original ciphertext oct with a ciphertext attribute y set_y；

A re-encryption key acquisition unit for acquiring an act containing an encryption key_y’And a tag tg_φThe re-encryption key rk of_x，y’The encryption key act_y’For the decryption key tdk with the key attribute x corresponding to the ciphertext attribute y set_xA tag tg generated by encrypting with a ciphertext attribute y' based on an attribute encryption method based on a set random number_φIs for utilizing said decryption key tdk_xTag tg for use in decrypting ciphertext_φSetting a random number;

a decryption tag generation unit for generating a decryption tag for the re-encryptionRe-encryption key rk acquired by key acquisition unit_x，y'The tag tg of_φDeforming to generate a decryption tag tg_vk(ii) a And

a re-encryption unit for performing attribute-based encryption on the original ciphertext oct acquired by the ciphertext acquisition unit using the ciphertext attribute y_yAnd the re-encryption key rk included in the re-encryption key rk acquired by the re-encryption key acquisition unit_x，y’The encryption key act in_y’And the decryption tag tg generated by the decryption tag generation unit_vkEncrypt to generate a re-encrypted ciphertext rct_y’。

5. The re-encryption apparatus according to claim 4,

the original ciphertext oct_yThe data vk is set to be the data vk,

the decryption tag generation unit generates the tag tg_φ^ setting the data vk and generating the decryption label tg_vk。

6. The re-encryption apparatus according to claim 4 or 5,

the decryption tag generation unit generates the decryption tag tg as shown in equation 3_vk，

The re-encryption unit generates the re-encrypted ciphertext rct as shown in equation 4_y’

[ formula 3]

Wherein

[ formula 4]

rct_y′＝(y′，c₃,c_T)

Wherein

7. A re-encrypted ciphertext decryption apparatus, comprising:

a re-encrypted ciphertext acquisition unit that acquires a re-encrypted ciphertext rct_y’The re-encrypted ciphertext rct_y’Uses the ciphertext attribute y' to the original ciphertext oct in an attribute-based encryption mode_yEncryption key act_y’And a decryption tag tg_vkGenerated by encrypting, wherein the original ciphertext oct_ySet with a ciphertext attribute y, the encryption key act_y’For the decryption key tdk with the key attribute x corresponding to the ciphertext attribute y set_xThe decryption tag tg is generated by encrypting with the ciphertext attribute y' based on the attribute encryption method based on the set random number_vkIs based on the fact that to use said decryption key tdk_xTag tg for use in decrypting ciphertext_φAnd then generated;

a1 st decryption unit that uses a decryption key adk to which a key attribute x 'corresponding to the ciphertext attribute y' is set_x’The re-encrypted ciphertext rct obtained by the re-encrypted ciphertext obtaining unit_y’Decrypting to generate the original ciphertext oct_yThe encryption key act_y’And said decryption tag tg_vk；

A 2 nd decryption unit for decrypting the encrypted data using the decryption key adk_x’For the encryption key act generated by the 1 st decryption unit_y’Performs decryption to generate a decryption key tdk with a random number set therein_xΛ; and

a 3 rd decryption unit that uses a decryption key tdk to which the random number generated by the 2 nd decryption unit is set_xΛ and the decryption tag tg_vkFor the original ciphertext oct_yDecryption is performed.

8. The re-encrypted ciphertext decryption apparatus of claim 7,

the re-encrypted ciphertext acquisition unit may acquire the re-encrypted ciphertext rct shown in equation 5_y’，

The 1 st decryption unit generates the original ciphertext oct as shown in equation 6_yThe encryption key act_y’And said decryption tag tg_vk，

The 2 nd decryption section generates the decryption key tdk as shown in equation 7_x，

The 3 rd decryption part is as shown in equation 8 for the original ciphertext oct_yCarry out decryption

[ formula 5]

rct_y′＝(y′，c₃，c_T)

Wherein

[ formula 6]

oct_y||act_y′||tg_vk＝c_T/K

Wherein

[ formula 7]

Wherein

act_y′＝(y′，c₃，c_T)，

[ formula 8]

m＝c_T/K

Wherein

oct_y＝tct_y，vk＝(y，c₀，c₁，c₂，c_T)，

9. A cryptographic system, comprising:

a key generation device for generating a decryption key adk having a tagged decryption key and a set key attribute x_xDecryption key dk of_xWherein the tagged decryption key comprises a decryption key tdk to which the key attribute x is set_xAnd in order to use said decryption key tdk_xTag tg for use in decrypting ciphertext_φ；

An encryption device that generates an original ciphertext oct that has a ciphertext attribute y set therein in correspondence with the key attribute x and that can be decrypted using the tagged decryption key generated by the key generation device_y(ii) a And

a re-encryption key generation device for encrypting the decryption key tdk generated by the key generation device by an attribute-based encryption method using the ciphertext attribute y_xEncrypted to generate as the re-encrypted ciphertext rct_y’Re-encryption key rk of the key of_x，y’The re-encrypted ciphertext rct_y’The decryption key adk with the key attribute x 'corresponding to the ciphertext attribute y' set therein can be used_x’Decryption is performed.

Technical Field

The invention relates to proxy-re-encryption (proxy-re-encryption).

Background

The attribute-based proxy re-encryption method is a method that can change the decryption authority of a ciphertext without decrypting the ciphertext. In the attribute-based encryption method, a key attribute x is set for a decryption key, and a ciphertext attribute y is set for a ciphertext. In the attribute-based encryption scheme, the ciphertext can be decrypted only when the key attribute x and the ciphertext attribute y satisfy the relationship R (x, y) ═ 1. In the attribute-based proxy re-encryption method, by using a re-encryption key, it is possible to change a ciphertext attribute y set for a ciphertext to another ciphertext attribute y' without decrypting the ciphertext.

Patent document 1 and non-patent document 1 describe a proxy re-encryption scheme based on an attribute.

Disclosure of Invention

Problems to be solved by the invention

In the proxy re-encryption method based on the attribute described in patent document 1 and non-patent document 1, the re-encrypted ciphertext includes a random matrix, and thus the size of the re-encrypted ciphertext increases.

The purpose of the present invention is to realize an attribute-based proxy re-encryption scheme that suppresses the increase in the size of a ciphertext associated with re-encryption.

Means for solving the problems

A re-encryption key generation device of the present invention includes: a randomizer for decrypting the decryption key tdk with the key attribute x_xAnd in order to use said decryption key tdk_xTag tg for use in decrypting ciphertext_φSetting a random number to generate a decryption key tdk_xΛ and label tg_φΛ; an encryption key generation unit that uses a ciphertext attribute y' to encrypt the decryption key tdk generated by the randomization unit in an attribute-based encryption method_xEncrypt for ^ to generate encrypted key act_y’(ii) a And a re-encryption key output unit that outputs an encryption key act including the encryption key generated by the encryption key generation unit_y’And the tag tg generated by the randomizing part_φLambda re-encryption key rk_x，y’。

Effects of the invention

In the invention, a decryption key encrypted based on the attribute of the tag is encrypted by using an encryption mode based on the attribute to serve as a re-encryption key. Thus, the random matrix does not need to be included in the re-encrypted ciphertext, and the increase in the ciphertext size associated with the re-encryption can be suppressed.

Drawings

Fig. 1 is a configuration diagram of a cryptographic system 1 according to embodiment 1.

Fig. 2 is a configuration diagram of the key generation device 10 according to embodiment 1.

Fig. 3 is a configuration diagram of the encryption device 20 according to embodiment 1.

Fig. 4 is a block diagram of the original ciphertext decryption apparatus 30 according to embodiment 1.

Fig. 5 is a configuration diagram of the re-encryption key generation apparatus 40 according to embodiment 1.

Fig. 6 is a configuration diagram of the re-encryption device 50 according to embodiment 1.

Fig. 7 is a configuration diagram of the re-encrypted ciphertext decryption apparatus 60 according to embodiment 1.

Fig. 8 is a flowchart of the Setup algorithm according to embodiment 1.

Fig. 9 is a flowchart of the KG algorithm of embodiment 1.

Fig. 10 is a flowchart of the Enc algorithm of embodiment 1.

Fig. 11 is a flowchart of the ODec algorithm of embodiment 1.

Fig. 12 is a flowchart of the RKG algorithm of embodiment 1.

Fig. 13 is a flowchart of the REnc algorithm of embodiment 1.

Fig. 14 is a flowchart of the RDec algorithm of embodiment 1.

Fig. 15 is a configuration diagram of the key generation device 10 according to modification 1.

Fig. 16 is a configuration diagram of an encryption device 20 according to modification 1.

Fig. 17 is a configuration diagram of the original ciphertext decryption apparatus 30 of modification 1.

Fig. 18 is a configuration diagram of a re-encryption key generation apparatus 40 according to modification 1.

Fig. 19 is a configuration diagram of the re-encryption device 50 according to modification 1.

Fig. 20 is a configuration diagram of the re-encrypted ciphertext decryption apparatus 60 according to variation 1.

Detailed Description