The Approximate Homomorphic Encryption scheme CKKS offers a distinctive and effective approach to privacy-preserving computation, with significant potential applications in IoT and machine learning domains. Recent advancements have introduced bootstrapping techniques tailored for CKKS, including the EvalMod and EvalRound bootstrapping techniques. These bootstrapping techniques mainly focus on approximate computation of modular reduction functions. However, the approximation of modular functions encounters challenges related to computational efficiency and bootstrapping precision, thus emerging as a major bottleneck in the advancement of bootstrapping techniques. Motivated by these concerns, in this paper, we introduce a novel bootstrapping scheme named EvalComp, which eliminates the need to fit modular functions. Unlike existing approaches, EvalComp constructs a homomorphic rounding function using the Homomorphic Comparison Function (HCF) and thus removes the integer multiples of the modulus$\boldsymbol {q}$from the ciphertext. For$\boldsymbol {N = {2^{9}}}$, EvalComp enhances bootstrapping precision by over 11 bits and computational efficiency by 16.7% compared with the latest EvalMod scheme (JM22). Additionally, compared with the EvalRound scheme (KPK22+), our scheme improves bootstrapping precision by 2-3 bits and computational efficiency by 20.2%. According to the bootstrapping performance comparison criterion, the performance of EvalComp achieves 1.80 times that of JM22 and 1.69 times that of KPK22+.

To enhance English language learning through descriptive tasks based on everyday life scenes, we propose leveraging multimodal Al technologies. This involves utilizing multimodal large language models to automatically assess the quality of student responses and provide personalized, timely feedback in the form of Al-driven comments and suggestions for improvement. Furthermore, we will investigate students' perceptions of the feedback provided and its effectiveness in enhancing their writing skills. To achieve this, 30 participants were recruited to describe a set of daily-life pictures with the Al-driven automated assistance. During the experiment, eye-tracking technology was employed to capture students' eye movement data, enabling analysis of their visual perception and attention allocation. A survey questionnaire was administered to gather students' perceptions of this language learning approach and the effectiveness of the feedback. The experimental results indicate that students exhibit a positive attitude towards this language learning approach, as evidenced by their high levels of learning interest and motivation. Moreover, students demonstrate a willingness to actively engage with automatic feedback, with a particular inclination towards investing more attention and time in the suggestions generated by a large language model.

As a kind of special proxy signature, directed proxy signature can be used to sign messages, such that only the designated verifier can easily verify the validity of the signature while others cannot. At the same time, if necessary, the proxy signer or designated verifier can prove the validity of the signature to any third party. However, the revocation of delegated rights has never been considered in the existing directed proxy signature schemes. In fact, in these directed proxy signature schemes, even if the period of delegation has expired, the proxy signer still can generate the valid proxy signature, and the original signer can do nothing to prevent it. Therefore, the authors give a solution to the delegation revocation problem and propose a directed proxy signature scheme with fast revocation in this study. The security and the invisibility of the authors’ scheme are proven based on the gap Diffie–Hellman assumption and under the decisional Diffie–Hellman problem in the standard model, respectively.

In earlier multi‐receiver signcryption schemes, in order to help the authorised receivers to find the corresponding information for decryption from the ciphertext, the list of identities of all authorised receivers should be included in the ciphertext as a necessary element. However, this method has directly led to the privacy leakage problem of receivers. Later, several anonymous multi‐receiver signcryption schemes use the Lagrange interpolation method to mix and hide the real identities of all receivers, so that the ciphertext does not expose identities of the receivers any longer. Therefore the Lagrange interpolation method is considered to be a perfect solution to the receiver anonymity problem, and multiple anonymous multi‐receiver signcryption schemes have been proposed based on it. However, recently, this method has been proven to be insecure because it cannot assure the anonymity of receivers either. In fact, in any of the existing anonymous schemes based on the Lagrange interpolation method, it is easy for one authorised receiver to judge whether anyone is an authorised receiver or not, which badly violates the receiver anonymity. Motivated by these concerns, the authors propose a new multi‐receiver signcryption scheme to solve this problem. Analyses show that the proposed scheme meets confidentiality, unforgeablity and the sender and receivers’ anonymity.

Fan et al . proposed an anonymous multi‐receiver identity‐based encryption scheme in 2010, and showed that the identity of any legal receiver can be kept anonymous to anyone else. In 2012, Wang et al . pointed out that Fan et al .’s scheme cannot achieve the anonymity and that every legal receiver can determine whether the other is one of the legal receivers. At the same time, they proposed an improved scheme based on Fan et al .’s scheme to solve this anonymity problem. Unfortunately, the authors find that Wang et al .’s improved scheme still suffers from the same anonymity problem. Any legal receiver of Wang et al .’s improved scheme can judge whether anyone else is a legal receiver or not. In this study, the authors shall give the detailed anonymity analysis of Wang et al .’s improved scheme.

Existing mobile authentication protocols are low in efficiency, because asymmetric encryption algorithms with large computational overheads are employed in these protocols to ensure user anonymity. In addition, the existing mobile authentication protocols have a long delay in fast reconnection, because these protocols may suffer from desynchronization attacks. In order to solve these problems, an efficient mutual authentication protocol with user anonymity for mobile networks is proposed. The proposed protocol ensures user anonymity by using one-way hash function. It reduces the delay time in fast reconnection, because once the session key between the mobile user and the foreign agent is found to be desynchronized in reconnection process, mobile users start the process of login and authentication from a new beginning immediately. The security of the proposed protocol is proved by using the provable security model. Compared with several existing authentication protocols for mobile networks, the proposed protocol is more secure and more effective.

Multicasting is an important business in the field of the wireless local area network (WLAN), because the access point (AP) usually has to send the same message to each station (STA) of a specific group, and broadcasting the message to this group is one of the most efficient ways of communication. Chinese WLAN security standard, called WLAN Authentication and Privacy Infrastructure (WAPI), has taken secure multicasting into account, and proposed a Multicast Key Management Protocol (MKMP), in which the multicast session key (MSK) is distributed to each STA over the secure unicast channel built between STA and AP one by one. It is clear that the MSK distribution is very inefficient in performance, especially when the number of STAs is very large. In this study, a new MSK distribution protocol is proposed, and it can be used to substitute the original protocol in WAPI. Analyses show that the proposed protocol can achieve needed security requirements, and is more efficient than the original one in WAPI. Now, WAPI has been in the process of ISO/IEC standard building, and thus the authors think that their proposal can ameliorate WAPI largely and promote its ISO/IEC standard building.

Since biometric data are unique and permanent characteristics of individuals, the privacy protection of biometric authentication schemes has become a common concern of the public. Recently, Tang et al. proposed a biometric-based authentication scheme in an attempt to solve the privacy concerns. However, their scheme cannot resist the attack of tamper. Motivated by these concerns, in this paper, we proposed a new biometric-based authentication scheme, which achieves identity privacy and transaction untraceability. Its security is based on the semantic security of the ElGamal algorithm. Analysis results show that our scheme is higher in efficiency than Tang et al. scheme does, and meanwhile, it can resist the tamper attack. It is concluded that the proposed scheme is more secure and more practical than the existing ones.

The tremendous evolution in networking, communication and mobility creates greater security assurance demand than can be provided by simple security measures, such as requiring passwords to gain access to a system. Biometric technologies are being used increasingly as an effective means. The combination of biometrics and cryptography is promising although there are some issues to be addressed. The key issue of the biometric encryption is how to deal with the contradiction about the veracity of cryptography and the simulation of biometric. The shielding function is a potential tool to solve this problem. In this paper, we shall review and analyze the classic biometrics-based cryptographic key management. And then, we construct a new fingerprint-based key binding scheme by using the shielding function and the WFMT method.