Keyword searchable delay encryption method and system

Abstract

The invention relates to a keyword searchable delayed encryption method and system. The method at least comprises the steps of generating a searchable ciphertext Cw and / or a file ciphertext for a keyword w of at least one to-be-uploaded file in a delayed encryption mode based on a public key PK, and uploading the searchable ciphertext Cw and / or the file ciphertext to a cloud server; at least one retrieval trap door Tw generated for the keyword w to be retrieved based on the private key SK is sent to a cloud server, the cloud server retrieves all the searchable ciphertexts Cw based on the retrieval trap door Tw to obtain the corresponding searchable ciphertexts Cw, and corresponding file ciphertexts are determined based on the searchable ciphertexts Cw obtained through retrieval and fed back to a receiving end. According to the method, the generation time of the searchable ciphertext is delayed, and the keyword guessing attack difficulty of an attacker is increased, so that the keyword guessing attack between the cloud server and the sending end and between the cloud server and the receiving end is realized in a scene without a secure channel, a specified trusted server, a priori keyword space and strict user authentication. The searchable public key encryption has the characteristic of resisting keyword guessing attack.

Description

technical field [0001] The present invention relates to the technical field of encryption and cloud storage, in particular to a keyword-searchable delayed encryption method and system. Background technique [0002] With the rapid development of cloud computing technology, cloud service providers provide users with convenient and reliable storage and computing services to meet the service demand of increasing data volume. In order to simultaneously protect the confidentiality and availability of user data stored in the cloud, searchable encryption technology emerges as the times require. Searchable encryption techniques are mainly divided into two categories, searchable symmetric encryption and searchable public key encryption. Searchable public key encryption benefits from the characteristics of the public key system, and is naturally suitable for non-interactive storage and retrieval between the sender and receiver. However, searchable public key encryption is inherently ...

AI Technical Summary

Problems solved by technology

It mainly includes the following four types, (1) Specifying a trusted server / server set, restricting the trapdoor test to be performed only by a specific server or jointly performed by a specific server set, so that external attackers cannot verify the guessed keywords; (2) Fuzzy keywords Retrieval, increasing the entropy of the keyword space, so that the attacker cannot obtain the exact keyword information according to the fuzzy trapdoor that is suspected of being exposed; (3) Restrict the sender, and embed the sender's private key in the searchable ciphertext to make the ciphertext inaccessible Forgery, only the searchable ciphertext generated by the sender specified in the trapdoor can perform the trapdoor test; (4) Restrict users, increase the strict restrictions on user identities by trusted institutions, and affect the construction of searchable ciphertext

[0004] For example, the patent document CN108599937B discloses a public key encryption method supporting multi-keyword search to solve the technical problem of complex ciphertext keyword calculation process existing in the existing multi-keyword searchable public key encryption method, and the implementation steps Including: (1) The trusted third party sets public parameters; (2) The data owner sets the key field, key vector and query format of the stored file; (3) The trusted third party calculates the cloud storage server and data sharer (4) The data owner encrypts and sends the plaintext keywords in the plaintext keyword vector; (5) The data sharer calculates and sends the trapdoor information of the plaintext keywords in the plaintext keyword vector; (6) The cloud storage server searches the ciphertext keywords in the ciphertext collection, and sends the searched ciphertext keywords to the data sharer

[0005] However, the above solutions generally have optimistic assumptions, which are often difficult to realize in the actual environment

Using the method of specifying a trusted server under the condition of no secure channel requires assuming that the server is safe and reliable. However, in practice, it is difficult to find a completely trusted server due to network attacks or profit-driven

Even if it is expanded to specify a set of trusted servers and split the trapdoor testing process, it is difficult to guarantee that there will be no collusion between them

The fuzzy keyword retrieval method needs to determine the entropy of the keyword space in advance, which leads to the loss of some flexibility in the selection of keywords

The method for the receiver to restrict the sender through the trapdoor is also lack of practicability. It is not easy for the receiver to know the trusted sender a priori, and it is necessary to construct a trapdoor for each sender, which greatly increases the communication overhead.

In addition, the introduction of trusted institutions to manage user identities and behaviors is also likely to cause additional costs

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