CN109525388B - Combined encryption method and system with separated keys - Google Patents

Abstract

The invention discloses a combined encryption method and a system with separated keys, which relate to the technical field of data security and computer networks, and the method comprises the following steps: the user terminal divides the data into a first data part and a second data part, and encrypts the first data part by using a terminal key acquired from a key distribution center KDC to obtain a first data part ciphertext; and the user terminal sends the first part of the data cipher text and the second part of the data to a server side, so that the server side encrypts the second part of the data by using a server side secret key acquired from the KDC to obtain a second part of the data cipher text.

Description

A combined encryption method and system for key separation

technical field

The invention relates to the technical field of data security and computer network, in particular to a combined encryption method and system for key separation.

Background technique

With the rapid development of mobile Internet and wireless network technologies, a large amount of digital data is generated every day, and people pay more and more attention to the privacy and security of data. Data encryption is one of the main means to protect privacy. On the one hand, in order to ensure data security, the encryption algorithms and keys used for encryption are becoming more and more complex, especially when the computing power of the device is limited, such as mobile phones, set-top boxes, etc., the encryption and decryption will take a long time and affect the experience; on the other hand, At present, encryption usually means that one party sets a key and then encrypts the file, and then stores the encrypted data and key on the server or set-top box. However, when the key is obtained by hackers, the user's sensitive information will be leaked. The computational performance requirements of the encryption party are very high. Therefore, in order to protect privacy and improve encryption and decryption efficiency, multi-party participation in key generation and data encryption and decryption will become a trend.

With the development of the mobile Internet, mobile phones are becoming more and more popular, and people can take pictures, shop and so on through mobile phones. But when people want to save life moments or photos on the server (such as network set-top box or cloud server, etc.), in order to protect privacy, the existing methods are divided into two categories: 1. Encrypt on the mobile phone, and then upload 2. Transfer the data to the server side, and the server side performs encrypted storage. However, both of the above two methods involve one party involved in the encryption and decryption of files, especially the first one, which requires high performance of the mobile phone, and when the key of this party is lost, the private information will be leaked, and the second one requires the server side The computing performance is very strong, but in the mobile Internet environment, the computing performance of the user terminal and the server side (not limited to the set-top box) is not very high. In addition, when a user wants to share encrypted data with other users, one way is to send the key to other users, but it increases the risk of leakage, and another way is to re-encrypt the document with the new key, but it increases storage space.

SUMMARY OF THE INVENTION

The technical problem solved by the solution provided according to the embodiment of the present invention is that the server with limited computing and storage capabilities has the risk of data security and privacy leakage and limited storage.

A combined encryption method for key separation provided according to an embodiment of the present invention includes:

The user terminal divides the data into the first part of the data and the second part of the data, and encrypts the first part of the data with the terminal key obtained from the key distribution center KDC (Key Distribution Center, key distribution center), and obtains the first part of the data. arts;

The user terminal sends the ciphertext of the first part of the data and the second part of the data to the server, so that the server encrypts the second part of the data by using the server key obtained from the KDC to obtain the data The second part of the ciphertext.

Preferably, before using the terminal key obtained from the key distribution center KDC to encrypt the first part of the data, the method further includes:

The user terminal receives the terminal key returned by the KDC according to the registration request by sending a registration request including server-side information to the KDC.

Preferably, the user terminal divides the data into the first part of the data and the second part of the data, and uses the terminal key obtained from the key distribution center KDC to encrypt the first part of the data, and the obtained ciphertext of the first part of the data includes:

The user terminal obtains the first part of the data, the second part of the data and the data division information by randomly dividing the data;

The user terminal encrypts the first part of the data by using the terminal key to obtain the ciphertext of the first part of the data.

Preferably, it also includes:

When viewing the data, decrypt the first part of the ciphertext and the second part of the data by using the terminal key and the server key respectively, and use the data segmentation information to splicing the decrypted plaintext , recover the data.

Preferably, when the user terminal views the data, the ciphertext of the first part of the data and the second part of the data are decrypted by using the terminal key and the server key respectively, and the data segmentation information is used to decrypt the data. The decrypted plaintext is spliced to recover the data including:

The user terminal receives the second part of plaintext obtained by decrypting the ciphertext of the second part of the data by the server using the server key;

After receiving the second part of the plaintext, the user terminal decrypts the ciphertext of the first part of the data by using the terminal key to obtain the first part of the plaintext;

The user terminal uses the data division information to splicing the obtained second part of the plaintext and the first part of the plaintext to recover the data.

A combined encryption method for key separation provided according to an embodiment of the present invention includes:

The server side receives the ciphertext of the first part of the data, the second part of the data and the data segmentation information sent by the user terminal, and encrypts the second part of the data in the ciphertext component by using the server-side key obtained from the KDC, to obtain The ciphertext of the second part of the data;

The server side stores the ciphertext of the first part of the received data, the data segmentation information, and the ciphertext of the second part of the obtained data.

A combined encryption system with key separation provided according to an embodiment of the present invention includes:

The user terminal is used to divide the data into the first part of the data and the second part of the data, and use the terminal key obtained from the key distribution center KDC to encrypt the first part of the data, and after the ciphertext of the first part of the data is obtained, the first part of the data is encrypted. A part of the ciphertext and the second part of the data are sent to the server;

The server side is configured to encrypt the second part of the data by using the server-side key obtained from the KDC to obtain the ciphertext of the second part of the data.

Preferably, the user terminal includes:

a dividing unit, configured to randomly divide the data to obtain the first part of the data, the second part of the data and the data division information;

The encryption unit is used for the user terminal to encrypt the first part of the data by using the terminal key returned by sending the registration request including the server-side information to the KDC to obtain the ciphertext of the first part of the data.

According to an embodiment of the present invention, a combined encryption device for key separation is provided. The device includes: a processor, and a memory coupled to the processor; The program for combined encryption of key separation, which is implemented when the program for combined encryption of key separation is executed by the processor includes:

Divide the data into the first part of the data and the second part of the data, and encrypt the first part of the data with the terminal key obtained from the key distribution center KDC to obtain the ciphertext of the first part of the data;

Send the ciphertext of the first part of the data and the second part of the data to the server, so that the server encrypts the second part of the data with the server-side key obtained from the KDC, and obtains the second part of the data encrypted. arts.

According to a computer storage medium provided by an embodiment of the present invention, a program for combined encryption of key separation is stored, and the implementation of the combined encryption program for key separation when executed by a processor includes:

Receive the ciphertext of the first part of the data, the second part of the data and the data segmentation information sent by the user terminal, and encrypt the second part of the data in the ciphertext component by using the server-side key obtained from the KDC to obtain the first part of the data. Two-part ciphertext;

The ciphertext of the first part of the received data, the data division information and the ciphertext of the second part of the obtained data are stored.

According to the solution provided by the embodiment of the present invention, during data encryption, the user terminal and the server participate in the data encryption at the same time, which can effectively improve the encryption and decryption efficiency. By adding an access control policy to the ciphertext component, multiple users are allowed to access the same encrypted data without sharing keys, which can reduce the storage capacity of the server.

Description of drawings

1 is a flowchart of a combined encryption method for key separation provided by an embodiment of the present invention;

2 is a schematic diagram of a combined encryption system for key separation provided by an embodiment of the present invention;

Fig. 3 is the encryption flow model diagram of the key separation provided by the embodiment of the present invention;

Fig. 4 is the decryption flow model diagram of the key separation provided by the embodiment of the present invention;

5 is a flowchart of a method for key separation provided by an embodiment of the present invention;

6 is a flowchart of a data encryption method for key separation provided by an embodiment of the present invention;

7 is a flowchart of a method for generating a user key for key separation provided by an embodiment of the present invention;

FIG. 8 is a flowchart of a method for accessing data with key separation provided by an embodiment of the present invention.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments described below are only used to illustrate and explain the present invention, but not to limit the present invention.

FIG. 1 is a flowchart of a combined encryption method for key separation provided by an embodiment of the present invention, as shown in FIG. 1 , including:

Step S101: the user terminal divides the data into the first part of the data and the second part of the data, and encrypts the first part of the data with the terminal key obtained from the key distribution center KDC to obtain the ciphertext of the first part of the data;

Step S102: the user terminal sends the ciphertext of the first part of the data and the second part of the data to the server, so that the server encrypts the second part of the data by using the server key obtained from the KDC , to get the ciphertext of the second part of the data.

Wherein, before using the terminal key obtained from the key distribution center KDC to encrypt the first part of the data, it also includes: the user terminal sends a registration request including server-side information to the KDC, and receives the KDC according to the registration request. The terminal key returned by the request.

Wherein, the user terminal divides the data into the first part of the data and the second part of the data, and encrypts the first part of the data by using the terminal key obtained from the key distribution center KDC to obtain the ciphertext of the first part of the data, including: the user terminal By randomly dividing the data, the first part of the data, the second part of the data and the data division information are obtained; the user terminal encrypts the first part of the data by using the terminal key to obtain the ciphertext of the first part of the data.

The embodiment of the present invention further includes: when viewing the data, decrypting the ciphertext of the first part of the data and the second part of the data by using the terminal key and the server key respectively, and using the data segmentation information The decrypted plaintext is spliced to recover the data.

Wherein, when the user terminal views the data, the ciphertext of the first part of the data and the second part of the data are decrypted by using the terminal key and the server key respectively, and the data segmentation information is used to decrypt the data. Splicing the decrypted plaintext to recover the data includes: receiving, by the user terminal, the second part of the plaintext obtained by decrypting the ciphertext of the second part of the data by the server using the server key; the After receiving the second part of the plaintext, the user terminal uses the terminal key to decrypt the ciphertext of the first part of the data to obtain the first part of the plaintext; the user terminal uses the data segmentation information to decrypt the obtained first part of the plaintext. The second part is spliced with the first part of the plaintext to recover the data.

A combined encryption method for key separation provided according to an embodiment of the present invention includes:

The server side receives the ciphertext of the first part of the data, the second part of the data and the data segmentation information sent by the user terminal, and encrypts the second part of the data in the ciphertext component by using the server-side key obtained from the KDC, to obtain The ciphertext of the second part of the data;

The server side stores the ciphertext of the first part of the received data, the data segmentation information, and the ciphertext of the second part of the obtained data.

FIG. 2 is a schematic diagram of a combined encryption system with key separation provided by an embodiment of the present invention. As shown in FIG. 2 , the system includes: a user terminal 201 for dividing data into a first part of data and a second part of data, and using a The key distribution center KDC obtains the terminal key to encrypt the first part of the data, and after obtaining the ciphertext of the first part of the data, sends the ciphertext of the first part of the data and the second part of the data to the server; The server-side key obtained by the KDC encrypts the second part of the data to obtain the ciphertext of the second part of the data.

Wherein, the user terminal 201 includes: a dividing unit for randomly dividing the data to obtain the first part of the data, the second part of the data and the data division information; The terminal key returned from the server-side information registration request encrypts the first part of the data to obtain the ciphertext of the first part of the data.

According to an embodiment of the present invention, a combined encryption device for key separation is provided. The device includes: a processor, and a memory coupled to the processor; The program for combined encryption of key separation, which is implemented when the program for combined encryption of key separation is executed by the processor includes:

Divide the data into the first part of the data and the second part of the data, and encrypt the first part of the data with the terminal key obtained from the key distribution center KDC to obtain the ciphertext of the first part of the data;

Send the ciphertext of the first part of the data and the second part of the data to the server, so that the server encrypts the second part of the data with the server-side key obtained from the KDC, and obtains the second part of the data encrypted. arts.

According to a computer storage medium provided by an embodiment of the present invention, a program for combined encryption of key separation is stored, and the implementation of the combined encryption program for key separation when executed by a processor includes:

Receive the ciphertext of the first part of the data, the second part of the data and the data segmentation information sent by the user terminal, and encrypt the second part of the data in the ciphertext component by using the server-side key obtained from the KDC to obtain the first part of the data. Two-part ciphertext;

The ciphertext of the first part of the received data, the data division information and the ciphertext of the second part of the obtained data are stored.

Fig. 3 is an encryption flow model diagram of key separation provided by an embodiment of the present invention, as shown in Fig. 3, including: (1) a user terminal registers a KDC and requests a key; (2) KDC distributes a key; (3) uploads Partially encrypted ciphertext components; (4) the server requests the key; (5) the KDC distributes the key.

Fig. 4 is a decryption process model diagram of key separation provided by an embodiment of the present invention, as shown in Fig. 3, including: (1) the user terminal (ciphertext owner) requests ciphertext access; (2) the server returns after partial decryption (3) the terminal authorizes the user to request the key; (4) the KDC distributes the key; (5) the terminal authorizes the user (ciphertext visitor) to request the ciphertext access; (6) the server sends the ciphertext access policy; (7) The KDC returns the ciphertext owner key to generate the intermediate value; (8) The server returns the plaintext data to the terminal authorized user.

The system proposed by the present invention includes components: user terminal, authorization terminal, server and KDC. Among them, the user terminal includes an encryption and decryption module and an access policy generation module; an authorized terminal, when the user terminal does not participate in the encryption and access policy generation process, and only participates in the decryption process, it is called an authorized terminal; the server side includes an encryption and decryption module, an access policy Policy management module; KDC includes key management module and access policy management module.

FIG. 5 is a flowchart of a method for key separation provided by an embodiment of the present invention, as shown in FIG. 5 , including:

S1: System initialization, the user terminal generates the ciphertext access policy, and sends the ciphertext access policy and application key to the KDC;

S2: KDC first generates the user terminal key and sends it to the user terminal, and then uses the ciphertext access policy sent by the user terminal to generate the user key to generate an intermediate value, and the KDC only saves the user key to generate the intermediate value;

S3: The user terminal splits the plaintext data, uses the key distributed by the KDC to encrypt part of the plaintext to generate ciphertext, and then the user sends the data segmentation information, access policy, ciphertext part and plaintext part to the server side together. The user needs to save the key;

S4: The server receives the ciphertext component sent by the user, and then applies to the KDC for a key;

S5: KDC receives the key application requested by the server, and then generates a key for the server and sends it to the server;

S6: The server side receives the key distributed by the KDC, encrypts the plaintext part of the ciphertext component, and then stores the ciphertext component containing the data segmentation information, ciphertext and access policy on the server side, and the server side needs to save its key;

S7: When the user terminal sends a decryption request, the server first determines whether the user is the owner of the ciphertext, if so, go to S8, and if the accessing user is not the owner of the ciphertext, go to S9-S11;

S8: The server uses its own key to decrypt its encrypted ciphertext part, and then sends the ciphertext component to the user terminal, and then the user terminal uses its own key to decrypt the encrypted part, and then divides the information according to the data merge and restore data;

S9: The authorized user first applies for a key to the KDC. When the authorized user sends a decryption request, the server first confirms whether the authorized user satisfies the access policy of the ciphertext. Then the authorized user sends his key to the server;

S10: After receiving the key of the authorized user, the server sends the authorized user key and the ciphertext access policy to the KDC. The KDC finds the ciphertext owner key corresponding to the authorized user according to the ciphertext access policy to generate an intermediate value, and then Send the value to the server;

S11: When the server receives the intermediate value, it uses its own key, authorized user key and ciphertext owner key to generate the middleware to decrypt the ciphertext, and then combine and restore the plaintext data according to the data segmentation information, and then send it to the authorized user.

FIG. 6 is a flowchart of a data encryption method for key separation provided by an embodiment of the present invention. As shown in FIG. 6 , during encryption, both a user terminal (not limited to a mobile phone) and a server with low performance (not limited to a set-top box) participate in the encryption. Encryption, key distribution by a KDC. The KDC sends a key to the user terminal and the server respectively. The user terminal divides the data, encrypts it with the key it owns, and sends the ciphertext and plaintext to the server, and the server uses the secret key it has. The key is used to encrypt the plaintext part and then store it. During decryption, both parties are required to participate in the correct decryption. In this way, two parties participate in encryption and decryption, which not only improves the efficiency, but also prevents system security weaknesses from being stored by one party and improves security. In addition, when users encrypt data, they can set an access control policy for the data, and the access control mechanism is managed by the server and KDC. When the user applies for a key to the KDC, the user submits the set access control policy. The access policy generates the corresponding key generation intermediate value. When the authorized user needs to access the encrypted file, the server applies to the KDC for the corresponding key generation intermediate value and the authorized user's key according to the access policy to decrypt the ciphertext and decrypt the plaintext data. Send it to authorized users, so that only one ciphertext is stored on the server side.

The technical contents of the embodiments of the present invention are described in detail below with reference to FIGS. 6 to 8 : Application scenario: secure sharing of photos (files) of network set-top boxes.

Key generation, as shown in Figure 7:

First, the system is initialized, and user terminals (including set-top boxes, mobile phones, etc.) register with the key distribution center KDC and request keys.

encryption, as shown in Figure 6:

User A is going to upload photos to the set-top box using a mobile phone for encrypted storage. The user obtains the key Ka from the KDC, and obtains the list of registered users (including the set-top box) on the set-top box from the key distribution center. Access policy (only users in the access policy can access the photos encrypted by user A, called authorized users), then user A sends the access policy to the KDC to generate a Ka for each user in the access policy to generate an intermediate value, Saved by KDC. Then the user randomly divides the picture file to generate two parts, PT1 and PT2, and retains the segmentation information, and uses Ka and encryption algorithms (not limited to AES, DES, etc.) to encrypt part of the plaintext data PT1 to generate ciphertext CT1, and then user A Send the ciphertext components (including ciphertext CT1, plaintext PT2, segmentation and encryption information, encryption algorithm, access policy, user A flag) to the set-top box. The set-top box receives the ciphertext component sent by user A, and encrypts the plaintext PT2 to generate ciphertext CT2 according to the segmentation information. Finally, the ciphertext component that stores the photo of user A on the set-top box includes ciphertext CT1, ciphertext CT2, segmentation and encryption information. , encryption algorithm, access policy, user A logo.

Access the data, as shown in Figure 8:

1. User A checks the encrypted photo CT stored on the set-top box on his mobile phone:

User A sends a photo access request to the set-top box. The set-top box first determines whether the identity mark of user A is the same as the owner mark in the ciphertext. If it is the same, it is proved to be user A. Then the set-top box first decrypts its encrypted part according to the segmentation and encryption information, Then the set-top box sends the partially decrypted ciphertext components to user A, and then user A decrypts the remaining ciphertext and splices two plaintext components according to the segmentation and encryption information, and finally restores the photo and displays it on the mobile phone client.

2. View the encrypted photo CT stored by user A on the set-top box

If the access policy in the ciphertext component includes the set-top box, you can view the picture as long as you enter the corresponding key on the set-top box. The process is as follows: the set-top box first decrypts its encrypted ciphertext part, and then sends the key and access policy to the set-top box. KDC, KDC generates user A's key according to the access policy and the key of the set-top box, and then sends it to the set-top box. The set-top box decrypts the remaining ciphertext components using user A's key, and finally obtains the photo uploaded by user A and displays it on the set-top box.

3. User B views the encrypted photo CT stored by user A on the set-top box

User B sends a request to the set-top box to access the encrypted photo CT of user A. The set-top box first determines whether user B is in the access policy in the CT. If not, the set-top box rejects the access of user B. If user B is in the access policy, user B Send the key to the set-top box, the set-top box sends the key of user B and the access policy to the KDC at the same time, and then the KDC generates the key of user A according to the intermediate value and sends it to the set-top box. The set-top box uses the key it has and the key of user A. And the split and encrypted information is decrypted to obtain a plaintext photo, which is sent to user B, and the end user B can view the photo on the terminal.

In the case of decryption 2 and 3, the key of user A generated on the set-top box is temporary and not stored. When an authorized user wants to access the encrypted photos of user A, the set-top box is chosen to fully undertake the decryption task, in order to ensure User A's key is not shared with authorized users, which better guarantees user A's privacy. In the case of decryption 1, the set-top box and user A are selected to participate in decryption at the same time, in order to improve the security while ensuring security. Decryption efficiency reduces the burden on both parties.

According to the solution provided by the embodiment of the present invention, the user terminal and the server side are encrypted by key separation, and the ciphertext component and the access policy are used to ensure that a ciphertext can be implemented for different users without sharing the key. Users can access, and on the premise of ensuring security, the storage overhead of the set-top box and the computational burden of both parties are reduced.

Although the present invention has been described in detail above, the present invention is not limited thereto, and various modifications can be made by those skilled in the art in accordance with the principles of the present invention. Therefore, all modifications made in accordance with the principles of the present invention should be understood as falling within the protection scope of the present invention.

Claims (8)

1. A key-separated combined encryption and decryption method comprises the following steps:

the user terminal randomly divides the data to obtain a first part of the data, a second part of the data and data division information, and encrypts the first part of the data by using a terminal key obtained from a key distribution center KDC to obtain a first part of data ciphertext;

the user terminal sends the first part of data cipher text, the second part of data and the data segmentation information to a server side, so that the server side encrypts the second part of data by using a server side key acquired from the KDC to obtain a second part of data cipher text;

When the user terminal needs to check the data, receiving a second part of a plaintext obtained by decrypting a second part of the ciphertext of the data by using the server key by the server;

after receiving the second part of the plaintext, the user terminal decrypts the ciphertext of the first part of the data by using the terminal secret key to obtain a first part of the plaintext; and also,

and splicing the obtained second part of the plaintext and the first part of the plaintext by using the data segmentation information to recover the data.

2. The method according to claim 1, further comprising, before encrypting the first part of the data with the terminal key obtained from the key distribution center KDC:

and the user terminal sends a registration request containing server side information to the KDC and receives a terminal key returned by the KDC according to the registration request.

3. The method of claim 2, wherein the user terminal splits the data into a first portion of data and a second portion of data, and the encrypting the first portion of data using a terminal key obtained from a key distribution center KDC to obtain a first portion of data ciphertext comprises:

the user terminal randomly divides the data to obtain a first data part, a second data part and data division information;

And the user terminal encrypts the first part of the data by using the terminal key to obtain a first part of data ciphertext.

4. A key-separated combined encryption and decryption method, comprising:

the server side receives a first part of data ciphertext, a second part of data and data segmentation information sent by the user terminal, and encrypts the second part of data by using a server side key acquired from the KDC to obtain a second part of data ciphertext;

the server side stores the received first part of data cipher text, the data segmentation information and the obtained second part of data cipher text;

when the server side receives the data checking request of the user terminal, the server side key is used for decrypting the second part of the data ciphertext, the decrypted second part of the data plaintext, the first part of the data ciphertext and the data segmentation information are sent to the user terminal, so that the user terminal can obtain the first part of the plaintext after decrypting the first part of the data ciphertext through the terminal key, and the decrypted second part of the plaintext and the decrypted first part of the plaintext are spliced through the data segmentation information to restore the data.

5. A key-separated combined encryption and decryption system comprising:

the user terminal is used for obtaining a first data part, a second data part and data segmentation information by randomly segmenting data, encrypting the first data part by utilizing a terminal key obtained from a key distribution center KDC to obtain a first data part ciphertext, then sending the first data part ciphertext, the second data part and the data segmentation information to a server end, receiving a second plaintext part obtained by the server end through decrypting the second data part ciphertext by utilizing the server end key when the user terminal needs to check the data, decrypting the first data part ciphertext by utilizing the terminal key after receiving the second plaintext part to obtain a first plaintext part, and splicing the obtained second plaintext part and the first plaintext part by utilizing the data segmentation information, recovering the data;

and the server side is used for encrypting the second part of the data by using the server side key acquired from the KDC to obtain a second part of data ciphertext, decrypting the second part of data ciphertext by using the server side key, and sending the decrypted second part of data plaintext to the user terminal.

6. The system of claim 5, the user terminal comprising:

the data dividing unit is used for randomly dividing the data to obtain a first data part, a second data part and data dividing information;

and the encryption unit is used for encrypting the first part of the data by using a terminal key returned by sending a registration request containing the server-side information to the KDC by the user terminal to obtain a first part ciphertext of the data.

7. A key-separated combination encryption and decryption apparatus, the apparatus comprising: a processor, and a memory coupled to the processor; the memory stores a key-separated combined encryption and decryption program which can run on the processor, and when executed by the processor, the key-separated combined encryption and decryption program realizes the key-separated combined encryption and decryption method according to any one of claims 1 to 3.

8. A computer storage medium storing a key-separated combined encryption and decryption program that realizes the key-separated combined encryption and decryption method according to any one of claims 1 to 3 when executed by a processor.

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