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Purpose: To improve the ability of energy harvester, a Helmholtz–Duffing oscillator with nonlinear capacitance is considered, which has an asymmetric characteristic. In this paper, we investigates the effect of potential function asymmetries on the dynamic behaviors under harmonic excitation. Method: The electromechanical coupling governing equations of Helmholtz–Duffing energy harvester is established. Then its dynamic response in the region of the primary resonance is sought by the harmonic balance method. Results: The performances of the presented asymmetric nonlinear primary resonance energy harvester and the linear stiffness system are compared. Results clearly demonstrate an improved bandwidth over a case which does not involve an asymmetric potential energy function. Conclusion: It is found that multiple-valued steady-state solutions of frequency-response equation can exist, indicating that the jump phenomenon occurs. Besides, the amplitude–frequency response curves have double-jumping phenomena by the bend, first to the left and then to the right. The influence of the stiffness parameters on the shape of the frequency-response curves is also discussed. It is observed that different shapes of frequency-response curves can exist. The approximate analytical outcomes are in good agreement with the numerical results.

Recently, a privacy-preserving technique called Privacy-Preserving Matrix Transformation (PPMT) is widely used to construct efficient privacy-preserving Verifiable (outsourced) Computation (VC) protocols for specific functions. This technique is first proposed and formalized by Salinas et al. in 2015, and it enjoys provable privacy and high efficiency. Although it seems that Salinas et al.'s PPMT scheme and the further modified scheme are elegant, we still need to take a step back and precisely discuss whether the PPMT schemes are suitable choices for VC protocols. Since Salinas et al. gave two concrete PPMT schemes to achieve the matrix-related VC in data protection and proved that their schemes are private (in terms of indistinguishability), and Zhou et al. devised a new type of PPMT scheme for the same purpose, we focus on exploring privacy of these three types of PPMT schemes. In this article, to achieve our object, we first propose the concept of a linear distinguisher and two constructions of the linear distinguisher algorithms. In particular, the linear distinguisher is a polynomial-time algorithm employed by an adversary to explore the privacy property of a cryptographic primitive. Then, we take these three PPMT schemes (including Salinas et al.'s original work, Yu et al.'s generalization and Zhou et al.'s variant) as targets and analyze their privacy property by letting an adversary make use of our linear distinguisher algorithms. The analysis results show that all these three types of transformations do not hold privacy even against passive eavesdropping (i.e., a ciphertext-only attack), and subsequently, the privacy-preserving VC protocols, based on any of these PPMT schemes, also do not hold the same privacy.

Text generation is a key component of many natural language tasks. Motivated by the success of generative adversarial networks (GANs) for image generation, many text-specific GANs have been proposed. However, due to the discrete nature of text, these text GANs often use reinforcement learning (RL) or continuous relaxations to calculate gradients during learning, leading to high-variance or biased estimation. Furthermore, the existing text GANs often suffer from mode collapse (i.e., they have limited generative diversity). To tackle these problems, we propose a new text GAN model named text feature GAN (TFGAN), where adversarial learning is performed in a continuous text feature space. In the adversarial game, GPT2 provides the “true” features, while the generator of TFGAN learns from them. TFGAN is trained by maximum likelihood estimation on text space and adversarial learning on text feature space, effectively combining them into a single objective, while alleviating mode collapse. TFGAN achieves appealing performance in text generation tasks, and it can also be used as a flexible framework for learning text representations.

To support secure data mining and privacy-preserving computation, partial access and selective computation on encrypted data are desirable. Functional encryption (FE) is a new paradigm of public-key encryption and allows authorized users to compute specific functions on encrypted data without knowing the data. However, in some FE schemes, a trusted central authority (CA) is required to generate secret keys for users according to the description of functions. In this paper, to reduce trust on the CA and protect users’ privacy, a privacy-preserving decentralized FE for inner product (PPDFEIP) scheme is proposed where multiple authorities co-exist and work independently without any interaction. Especially, to resist collusion attacks, all secret keys of the same user are tied to his/her global identifier (GID), but authorities cannot know any information of the GID even if they collaborate. We formalize the definition and security model of our PPFEIP scheme, and propose a concrete construction. Furthermore, the proposed scheme is implemented and evaluated. Finally, the security of our PPDFEIP scheme is reduced to well-known complexity assumptions. The novelty is to reduce trust on the CA, protect users’ privacy and enable authorized users to compute inner product on encrypted data without compromising confidentiality.