Internet of Things (IoT) devices are leading to advancements in innovation, efficiency, and sustainability across various industries. However, as the number of connected IoT devices increases, the risk of intrusion becomes a major concern in IoT security. To prevent intrusions, it is crucial to implement intrusion detection systems (IDSs) that can detect and prevent such attacks. IDSs are a critical component of cybersecurity infrastructure. They are designed to detect and respond to malicious activities within a network or system. Traditional IDS methods rely on predefined signatures or rules to identify known threats, but these techniques may struggle to detect novel or sophisticated attacks. The implementation of IDSs with machine learning (ML) and deep learning (DL) techniques has been proposed to improve IDSs’ ability to detect attacks. This will enhance overall cybersecurity posture and resilience. However, ML and DL techniques face several issues that may impact the models’ performance and effectiveness, such as overfitting and the effects of unimportant features on finding meaningful patterns. To ensure better performance and reliability of machine learning models in IDSs when dealing with new and unseen threats, the models need to be optimized. This can be done by addressing overfitting and implementing feature selection. In this paper, we propose a scheme to optimize IoT intrusion detection by using class balancing and feature selection for preprocessing. We evaluated the experiment on the UNSW-NB15 dataset and the NSL-KD dataset by implementing two different ensemble models: one using a support vector machine (SVM) with bagging and another using long short-term memory (LSTM) with stacking. The results of the performance and the confusion matrix show that the LSTM stacking with analysis of variance (ANOVA) feature selection model is a superior model for classifying network attacks. It has remarkable accuracies of $96.92\%$ and $99.77\%$ and overfitting values of $0.33\%$ and $0.04\%$ on the two datasets, respectively. The model’s ROC is also shaped with a sharp bend, with AUC values of $0.9665$ and $0.9971$ for the UNSW-NB15 dataset and the NSL-KD dataset, respectively.

Email serves as the primary mode of communication in today’s interconnected digital world, encompassing business, education, and interpersonal relationships. However, email’s reliance on shared media makes it susceptible to interception and misuse of confidential data. Pretty Good Privacy (PGP) protects the privacy of email contents to address this problem. While PGP offers encryption, its key sharing has weaknesses. Blockchain technology is characterized by its immutability feature. Once information is stored in the blockchain, altering it becomes extremely difficult. This characteristic serves as a valuable defense against weaknesses in the PGP key sharing system. Furthermore, the implementation of smart contracts eliminates the need for a Man-in-the-Middle when sharing keys, thereby improving the security of key sharing and fostering trust among individuals. Blockchain and smart contracts improve security, but privacy remains a concern. To further bolster privacy protection, in this paper we propose the integration of Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zk-SNARKs) and blockchain into PGP key sharing mechanism. zk-SNARKs enable efficient verification of encrypted data without revealing sensitive information, thus preventing exposure of user privacy. Additionally, we employ Elliptic Curve Cryptography (ECC) in order to guarantee the confidentiality of the PGP key. Through this holistic integration, the security of the PGP key is enhanced, ensuring both confidentiality and integrity while safeguarding user privacy. Furthermore, gas consumption and transaction costs were evaluated with and without zk-SNARKs. The results demonstrate that the proposed mechanism minimizes gas consumption and transaction costs.

A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits.

Vehicular Ad-Hoc Networks (VANETs) play an essential role in the intelligent transportation era, furnishing users with essential roadway data to facilitate optimal route selection and mitigate the risk of accidents. However, the network exposure makes VANETs susceptible to cyber threats, making authentication crucial for ensuring security and integrity. Therefore, joining entity verification is essential to ensure the integrity and security of communication in VANETs. However, to authenticate the entities, authentication time should be minimized to guarantee fast and secure authentication procedures. We propose an authentication system for VANETs using blockchain and Kerberos for storing authentication messages in a blockchain ledger accessible to Trusted Authentication Servers (TASs) and Roadside Units (RSUs). We evaluate the system in three diverse network scenarios: suburban, urban with 1 TAS, and urban with 2 TASs. The findings reveal that this proposal is applicable in diverse network scenarios to fulfill the network requirements, including authentication, handover, and end-to-end delay, considering an additional TAS for an increasing number of vehicles. The system is also practicable in storing the authentication message in blockchain considering the gas values and memory size for all scenarios.

Software-Defined Networking (SDN) has revolutionized network management by separating the control and data planes; nevertheless, this architectural centralization introduces significant security vulnerabilities. To mitigate these risks, Intrusion Detection Systems (IDSs) are widely deployed in SDN environments; however, traditional rule-based IDSs struggle to address the dynamic, programmable, and evolving nature of SDN traffic. While machine learning-based IDSs enhance detection capabilities, aggregating sensitive network data across multiple organizational domains introduces a significant privacy-security trade-off, where global threat intelligence undermines individual organizations’ data confidentiality. This conflict necessitates a transition to privacy-preserving, distributed architectures that enable collaborative intelligence without exposing raw, sensitive data. Federated learning (FL) offers a promising alternative by enabling collaborative model training. However, standard FL implementations are still vulnerable to gradient leakage, poisoning, and impersonation attacks during communication between the aggregation server and distributed clients. To address the data privacy and security challenges, this paper proposes a secure, end-to-end FL-based IDS framework that integrates homomorphic encryption (HE). The architecture enables the secure aggregation of encrypted local updates without intermediate decryption, ensuring strict data residency and confidentiality. To further harden the system, cryptographic hashing and authentication tokens are used to verify message integrity and mitigate replay attacks. Finally, a Byzantine-resilient validation mechanism is incorporated to safeguard the global model against adversarial model poisoning and malicious participants. We rigorously evaluated the framework utilizing a Gated Recurrent Unit (GRU) model across three diverse threat landscapes: InSDN, CICDDoS2017, and CICDDoS2019. Experimental results demonstrate that the HE-enhanced FL model successfully breaks the traditional privacy-utility trade-off. It achieves exceptional detection accuracies of 99.94% on InSDN, 99.08% on CICDDoS2017, and 99.62% on CICDDoS2019. Furthermore, system-level analysis shows that this multi-layered cryptographic protection incurs only a slight computational overhead, with a predictable 16.57-fold increase in communication cost, confirming the framework’s practicality and scalability for secure SDN-based collaborative threat detection.

A ring oscillator is a well-known circuit used for generating random numbers, and interested readers can find many research results concerning the evaluation of the randomness with a packaged test suit. However, the authors think there is room for evaluating the unpredictability of a sequence from another viewpoint. In this paper, the authors focus on Wold’s RO-based generator and propose a statistical test to numerically evaluate the randomness of the RO-based generator. The test adopts the state transition probabilities in a Markov process and is designed to check the uniformity of the probabilities based on hypothesis testing. As a result, it is found that the RO-based generator yields a biased output from the viewpoint of the transition probability if the number of ROs is small. More precisely, the transitions $01\to 01$ and $11\to 11$ happen frequently when the number l of ROs is less than or equal to 10. In this sense, $l>10$ is recommended for use in any application, though a packaged test suit is passed. Thus, the authors believe that the proposed test contributes to evaluating the unpredictability of a sequence when used together with available statistical test suits, such as NIST SP800-22.