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In the traditional ciphertext-policy attribute-based encryption (CP-ABE) scheme,the access policy exists together with the ciphertext.This may leak the privacy of the data owner and bring potential security risks to the data owner in medicalscena-rios Therefore,solutions supporting access policy hiding have been proposed.However,most solutions need to generate redundant ciphertexts or key components in the process of implementing the decryption test,which increases the computing overhead of data owners and the storage overhead of data users.At the same time,malicious users may be motivated by its own interest to reveal their decryption keys.In order to solve the problems above,a lightweight medical data sharing scheme with access policy hiding and key tracking is proposed.Firstly,part of the master key is stored in the Enclave in advance by using software guard extensions(SGX) technology,so that the test results can be calculated accurately and quickly,and the generation of redundant ciphertexts and key components are avoided.Then,verifiable outsourcing technology is employed to reduce user's computing overhead,ensuring the correctness and completeness of decryption result.Finally,key tracking is realized by embedding the identity identifier in the decryption key of the data user.Performance analysis shows that the proposed scheme has certain advantages in terms of function and computing.The security analysis proves that the proposed scheme is secure under the selected plaintext attack.

In this article, theoretical modeling and vibration characteristics of a spinning double-blade beam assembly restricted by elastic supports are studied. Graphene nanoplatelet (GPL) reinforcement and porous foamed metal matrix are adopted to make up the assembly structure. Due to the nonuniformity of the porosity and graphene nanofillers, the material properties of the attached blades and beam are considered to change along the blade thickness and beam radius, respectively. They are obtained via the rule of mixture, the open-cell scheme and the Halpin-Tsai micromechanics model. These attached blades and beam are modeled in accordance with the Euler-Bernoulli beam theory and the Rayleigh beam theory, respectively. Via employing the Lagrange's equation, the equations of motion of the double-blade beam are derived. Then, the natural frequencies of the spinning nanocomposite double-blade beam are calculated by the substructure modal synthesis method and the assumed modes method. A detailed parameter analysis is performed to study the influences of dimension, distribution pattern and weight fraction of GPLs, distribution and coefficient of porosity, length and location of the blades, stiffness and location of supports, and spinning speed on the mechanical behaviors of the double-blade beam assembly. [ABSTRACT FROM AUTHOR]