Biblio

Fully homomorphic encryption (FHE) provides effective security assurance for privacy computing in cloud environments. But the existing FHE schemes are generally faced with challenges including using single-bit encryption and large ciphertext noise, which greatly affects the encryption efficiency and practicability. In this paper, a low-noise FHE scheme supporting multi-bit encryption is proposed based on the HAO scheme. The new scheme redesigns the encryption method without changing the system parameters and expands the plaintext space to support the encryption of integer matrices. In the process of noise reduction, we introduce a PNR method and use the subGaussian distribution theory to analyze the ciphertext noise. The security and the efficiency analysis show that the improved scheme can resist the chosen plaintext attack and effectively reduce the noise expansion rate. Comparative experiments show that the scheme has high encryption efficiency and is suitable for the privacy-preserving computation of integer matrices.

Ciphertext storage can effectively solve the security problems in cloud storage, among which the ciphertext policy attribute-based encryption (CP-ABE) is more suitable for ciphertext access control in cloud storage environment for it can achieve one-to-many ciphertext sharing. The existing attribute encryption scheme CP-ABE has problems with revocation such as coarse granularity, untimeliness, and low efficiency, which cannot meet the demands of cloud storage. This paper proposes an RCP-ABE scheme that supports real-time revocable fine-grained attributes for the existing attribute revocable scheme, the scheme of this paper adopts the version control technology to realize the instant revocation of the attributes. In the key update mechanism, the subset coverage technology is used to update the key, which reduces the workload of the authority. The experimental analysis shows that RCP-ABE is more efficient than other schemes.