A group-based metadata protection multi-party file sharing method

Abstract

This invention relates to a group-based metadata protection method for multi-party file sharing. The method includes the following steps: a user terminal generates file data to be shared and performs end-to-end encryption on the file data using a file encryption key to obtain a ciphertext file; the user terminal generates an encrypted index for the ciphertext file and uploads the ciphertext file and its index to a cloud storage server; the cloud storage server constructs an ORAM storage structure; the user terminal initiates a file access request; a proxy server authenticates the access request; the proxy server performs a proxy re-encryption operation according to the access policy to obtain re-encrypted data and generate an access token; the cloud storage server performs an ORAM access operation based on the access token to obtain the re-encrypted data; and the cloud storage server returns the re-encrypted data to the user terminal. Compared with existing technologies, this invention has advantages such as improved system privacy protection capabilities and operational efficiency.

Description

Technical Field

[0001] This invention relates, and more particularly, to a group-based metadata protection method for multi-party file sharing. Background Technology

[0002] With the rapid development of cloud computing and data sharing technologies, more and more organizations and users are storing data on cloud servers and achieving cross-regional data sharing and collaborative access via networks. This cloud storage and sharing model greatly improves the flexibility and efficiency of data management and has been widely used in scenarios such as medical data sharing, enterprise collaborative office work, and scientific research data management. However, as the scale of data sharing continues to expand, a large amount of sensitive data is being transmitted and stored over the network, and data privacy protection issues are becoming increasingly prominent.

[0003] In traditional cloud storage environments, users typically rely on cloud servers for data storage, index management, and access control. However, cloud servers are often considered "honest but curious" entities; while they can correctly execute operations according to protocols, they may infer sensitive information by analyzing user access behavior. For example, servers can infer user identities, data access patterns, and behavioral characteristics by observing metadata such as the time, frequency, and path of file access. Even if the data content is encrypted, metadata such as access patterns can still leak a large amount of private information, posing serious privacy and security risks.

[0004] To protect data security, existing technologies typically employ end-to-end encryption (E2EE) mechanisms, ensuring that only authorized users can decrypt and access the data. However, end-to-end encryption only protects the data content itself and cannot hide user access behavior and patterns. Therefore, in a multi-user shared environment, even if the data content is encrypted, the server can still infer the sharing relationships and access behaviors between users by analyzing access patterns, leading to metadata leakage.

[0005] To address the problem of access pattern leakage, researchers have recently proposed Oblivious Random Access Memory (ORAM) technology. ORAM randomizes data access paths, making it impossible for servers to distinguish between different data access requests, thus hiding the true access pattern. Several ORAM structures have been proposed, such as Path ORAM. While these techniques can hide access patterns to some extent, they still incur high computational and communication overhead in multi-user shared environments and lack mechanisms to protect user identity relationships and group access relationships.

[0006] Furthermore, in multi-user data sharing scenarios, it is also necessary to support dynamic user joining and revocation. Existing solutions typically employ proxy re-encryption (PRE) or group key management mechanisms to implement access control. However, when a user is revoked, traditional solutions usually require re-encrypting a large amount of data or updating the access key, which leads to high computational costs and system overhead, severely impacting system scalability and actual deployment efficiency.

[0007] Existing related research mainly includes the following types of technologies: Document 1: Stefanov E., van Dijk M., Shi E., et al. “Path ORAM: AnExtremely Simple Oblivious RAM Protocol.” In Proceedings of the ACMConference on Computer and Communications Security (CCS), 2013, pp. 299–310.

[0008] Document 2: Wang X., Chan THH, Shi E. “Circuit ORAM: On Tightness of the Goldreich-Ostrovsky Lower Bound.” In Proceedings of the ACM Conference on Computer and Communications Security (CCS), 2015.

[0009] Document 3: Popa RA, Redfield CM, Zeldovich N., et al. “CryptDB: Protecting Confidentiality with Encrypted Query Processing.” In Proceedings of the ACM Symposium on Operating Systems Principles (SOSP), 2011.

[0010] Document 4: Green M., Ateniese G. “Identity-Based Proxy Re-Encryption.” InApplied Cryptography and Network Security (ACNS), 2007.

[0011] While the above methods have made some progress in data privacy protection, they still have the following shortcomings: (1) Most solutions only focus on the encryption protection of data content, and it is difficult to effectively hide metadata such as user access patterns; (2) The existing ORAM structure is inefficient in a multi-user sharing environment and is difficult to meet the needs of large-scale group sharing scenarios; (3) When users dynamically join or withdraw, the traditional key update mechanism requires a large number of data re-encryption operations, resulting in a large system overhead; (4) The lack of privacy protection mechanisms for user identity relationships and group access relationships may still lead to the leakage of user behavior associations. Summary of the Invention

[0012] The purpose of this invention is to provide a group-based metadata protection method for multi-party file sharing, and to support a secure file sharing system and method with dynamic user management, so as to improve the system's privacy protection capabilities and operating efficiency.

[0013] The objective of this invention can be achieved through the following technical solutions: Compared with the prior art, the present invention has the following beneficial effects: This invention introduces an anonymous access tagging mechanism, an adaptive ORAM path scheduling mechanism, and a progressive key update mechanism. By dynamically generating anonymous access identifiers, optimizing the distribution of ORAM access paths, and triggering key rotation on demand, it effectively improves the system's metadata privacy protection capabilities and operational efficiency. Regarding dynamic user management, this invention designs a progressive key update mechanism. When user permissions change, the system does not need to immediately re-encrypt all data; instead, it gradually updates the key as the user accesses the data, thereby significantly reducing system computational overhead. Attached Figure Description

[0014] Figure 1 This is a diagram of the architecture of the group-based metadata protection multi-party file sharing system of the present invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0016] This invention belongs to the field of data security and privacy protection technology, specifically relating to a multi-user collaborative file sharing method and system based on metadata protection. This method integrates end-to-end encryption and inadvertent random access memory (JOTL-ORAM) technology. End-to-end encryption ensures the confidentiality of shared data content, while inadvertent random access hides user access patterns and identity information, thereby effectively protecting critical metadata during file sharing. Simultaneously, an optimized JOTL-ORAM structure improves system random access efficiency and reduces communication overhead, thus significantly enhancing data security and system performance in multi-party file sharing environments. This invention can be widely applied in fields with high data privacy protection requirements, such as cloud storage services, medical data sharing, government information collaboration, and enterprise data collaboration.

[0017] This invention constructs a data management architecture based on JOTL-ORAM and combines it with a proxy re-encryption and multi-party key negotiation mechanism to achieve comprehensive protection of key metadata such as file access patterns, user identities, and data association relationships.

[0018] To further enhance system security, this invention proposes a two-layer metadata protection mechanism. The first layer hides user access patterns by randomizing the ORAM access path; the second layer dynamically anonymizes user identities through an anonymous access tag mechanism, preventing the server from establishing long-term user behavior associations.

[0019] Furthermore, this invention proposes an adaptive ORAM path scheduling mechanism. This mechanism dynamically calculates access paths based on system access frequency and ORAM tree structure load, thereby achieving a uniform distribution of data access within the ORAM structure, reducing the probability of path conflicts, and mitigating the risk of stash overflow.

[0020] In terms of dynamic user management, this invention designs a progressive key update mechanism. When user permissions change, the system does not need to immediately re-encrypt all data, but instead gradually updates the key as the user accesses the data, thereby significantly reducing system computational overhead.

[0021] Furthermore, this invention proposes an access pattern perturbation mechanism. By generating random access requests and mixing them with real access operations, the system makes it difficult for the server to distinguish real access behavior through traffic analysis, thereby further enhancing the system's resistance to access pattern analysis attacks.

[0022] To make the technical means and effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] like Figure 1As shown, this embodiment of the invention provides a multi-party secure file sharing system based on metadata protection. The system mainly comprises three parts: a user terminal, a proxy server, and a cloud storage server.

[0024] 1. User Terminal: The user terminal is the data owner or data accessor in the system. It can be a computer, mobile phone, tablet, or other smart device with network communication capabilities. The user terminal is primarily responsible for encrypting and decrypting file data, generating keys, and initiating file access requests.

[0025] 2. Proxy Server: The proxy server sits between the user terminal and the cloud storage server, and is used to perform access control and encryption conversion operations. The proxy server is responsible for performing proxy re-encryption operations, verifying user access requests, and generating anonymous access tags to hide the user's real identity information.

[0026] 3. Cloud Storage Server: The cloud storage server is used to store encrypted file data and ORAM structure data. The cloud storage server responds to user access requests according to the ORAM access protocol, but cannot obtain the user's actual access mode, thus ensuring the privacy of user access behavior.

[0027] In this embodiment, the cloud storage server internally includes the following modules: (1) Data storage module: used to store file data after end-to-end encryption. (2) ORAM access module: used to implement the ORAM access protocol and perform path randomization processing on user data access requests. (3) Index management module: used to maintain file index information and cooperate with the ORAM access module to complete data retrieval. (4) Access perturbation module: used to generate random access requests to confuse the real access mode.

[0028] The method for secure multi-party file sharing based on metadata protection in this embodiment of the invention includes the following steps: Step 1: The user terminal generates file data to be shared and performs end-to-end encryption on the file data. In this embodiment, the data owner uses a symmetric key algorithm to encrypt the file, obtaining a ciphertext file. The encrypted file can only be accessed by authorized users possessing the corresponding key.

[0029] Step 2: The user terminal generates an encrypted index for the file and uploads the encrypted file and its index to the cloud storage server. In this step, the system generates a unique file identifier for each file and stores the file identifier and file location mapping relationship in the ORAM structure.

[0030] Step 3: The cloud storage server constructs an ORAM storage structure to hide the data access path. In this embodiment, the ORAM structure adopts a tree-like storage structure, with each data block randomly mapped to a path. When a user accesses data, the system randomly accesses a path and reassigns the data block's position, thereby hiding the true access pattern.

[0031] Step 4: The user terminal initiates a file access request. When accessing a file, the user needs to first send an access request to the proxy server. The access request contains the user's identity information and the target file identifier.

[0032] Step 5: The proxy server authenticates the access request and generates an anonymous access tag; in this embodiment, the anonymous access tag is generated in the following way: in: ID represents a user's identity identifier; Epoch represents the system time period; r represents a random number; H represents a hash function.

[0033] Anonymous tagging can effectively prevent servers from inferring user identity and behavioral relationships through multiple access records.

[0034] Step 6: The proxy server performs proxy re-encryption operation according to the access policy and generates an access token; the proxy server performs proxy re-encryption operation on the encrypted data according to the user's access permissions, so that legitimate users can decrypt the access data, while ensuring that the proxy server cannot obtain plaintext information.

[0035] Step 7: The cloud storage server performs an ORAM access operation based on the access token. In this step, the ORAM access module accesses the corresponding data block based on the access token and randomly selects an access path. Simultaneously, the system updates the location mapping of the data block within the ORAM structure.

[0036] Step 8: The cloud storage server returns encrypted data to the user terminal; after receiving the encrypted data, the user terminal uses the corresponding decryption key to decrypt it, thereby obtaining the original file data.

[0037] In this invention, the ORAM access process in step 7 specifically includes the following sub-steps: Step a: Determine the target data block based on the access token; Step b: Randomly select an access path from the ORAM tree structure; Step c: Read all data blocks on this path and temporarily store them in the local cache; Step d: Retrieve the target data block from the cache and return it to the user; Step e involves remapping the accessed data blocks to new path locations using random methods.

[0038] Through the above process, the server cannot infer the actual access data from the access path, thus achieving access mode hiding.

[0039] In this embodiment, the system also designs an adaptive ORAM path scheduling mechanism, the specific implementation of which includes: 1. Monitor the current access load of the system; the system provides real-time statistics on the number of ORAM access requests and the data block cache utilization rate.

[0040] 2. Calculate the ORAM loading factor; the formula for calculating the loading factor is as follows: AccessCount represents the current number of access requests, and Capacity represents the system's maximum access capacity.

[0041] 3. Dynamically adjust the access path selection strategy based on the load factor; when the system load is high, the system increases the randomness of the path to reduce access conflicts; when the system load is low, the system reduces the number of random accesses to improve access efficiency.

[0042] This invention also designs a progressive key update mechanism, the specific implementation of which is as follows: 1. When a user's access permissions are revoked, the system generates a new file encryption key; 2. The system checks the file key version when a user accesses a file; 3. If the file still uses the old key, perform the following update operation: in: Indicates old ciphertext; Indicates the old key; Indicates the new key; This indicates the updated ciphertext.

[0043] By updating the key gradually during the access process, the high computational overhead caused by re-encrypting all data all at once in traditional schemes can be avoided.

[0044] Furthermore, this invention introduces an access pattern perturbation mechanism to enhance the system's resistance to traffic analysis attacks. This mechanism improves the indistinguishability of access patterns by randomly generating fake access requests within the system, thus mixing real access requests into the random access sequence.

[0045] The effects and benefits of the embodiments: As can be seen from the above embodiments, the present invention protects data content security through end-to-end encryption technology and hides data access patterns by combining ORAM technology, thereby achieving dual privacy protection for data content and access behavior. Simultaneously, the anonymous access tag mechanism effectively hides user identity information and behavioral relationships, the adaptive ORAM path scheduling mechanism improves system access efficiency, and the progressive key update mechanism reduces system computational overhead when a user withdraws their data. Furthermore, the access pattern perturbation mechanism further enhances the system's ability to resist traffic analysis attacks. Therefore, the present invention improves the efficiency and scalability of multi-party file sharing systems while ensuring system security.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

[0047] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A group-based metadata protection method for multi-party file sharing, characterized in that, The method includes the following steps: The user terminal generates file data to be shared and performs end-to-end encryption on the file data using the file encryption key to obtain a ciphertext file. The user terminal generates an encrypted index for the encrypted file and uploads the encrypted file and its index to the cloud storage server; Cloud storage servers construct an ORAM storage structure, which hides the data access path of encrypted files. The user terminal initiates a file access request; The proxy server authenticates access requests, and generates an anonymous access tag if the authentication is successful. The proxy server performs a proxy re-encryption operation according to the access policy, obtains the re-encrypted data, and generates an access token; The cloud storage server performs an ORAM access operation based on the access token to obtain re-encrypted data; The cloud storage server returns re-encrypted data to the user terminal.

2. The method for protecting multi-party file sharing based on group metadata according to claim 1, characterized in that, The file access request includes user identity information and target file identifier.

3. The method for protecting multi-party file sharing based on group metadata according to claim 1, characterized in that, Anonymous access tags are: Where ID represents the user's identity identifier; Epoch represents the system time period; r represents a random number; and H represents a hash function.

4. The method for multi-party file sharing based on group-based metadata protection according to claim 1, characterized in that, The ORAM structure uses a tree-like storage structure.

5. A group-based metadata protection method for multi-party file sharing according to claim 1, characterized in that, Each data block of the encrypted file is randomly mapped to a path in a tree-like storage structure.

6. A method for protecting multi-party file sharing based on group metadata according to claim 1, characterized in that, The specific steps by which the cloud storage server performs an ORAM access operation based on the access token to obtain the re-encrypted data are as follows: The cloud storage server accesses the corresponding re-encrypted data block based on the access token and randomly selects an access path to obtain the re-encrypted data.

7. A group-based metadata protection method for multi-party file sharing according to claim 6, characterized in that, While performing ORAM access operations, update the location mapping of the data blocks of re-encrypted data in the ORAM structure.

8. A group-based metadata protection method for multi-party file sharing according to claim 7, characterized in that, The cloud storage server accesses the corresponding re-encrypted data block based on the access token and randomly selects an access path to obtain the re-encrypted data. The specific steps are as follows: Step a: Determine the data block corresponding to the re-encrypted data based on the access token; Step b: Randomly select an access path from the ORAM tree structure; Step c: Read all data blocks on this path and temporarily store them in the local cache; Step d: Retrieve the data block corresponding to the re-encrypted data from the cache and return it to the user; Step e involves remapping the accessed data blocks to new path locations using random methods.

9. A group-based metadata protection method for multi-party file sharing according to claim 8, characterized in that, When a random access path is selected, the randomness of the path increases when the ORAM load factor exceeds the threshold, and decreases when it does not.

10. A group-based metadata protection method for multi-party file sharing according to claim 1, characterized in that, The method also includes: When a user's access permissions are revoked, a new file encryption key is generated. When authenticating an access request, the proxy server checks the file encryption key version; If the key is old, then perform the update operation.

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