Blockchain is expected to play a key role in securing next generation communication systems, i.e., B5G and 6G, which will be highly decentralised, with high integration of edge computing, device-to-device (D2D) communications, and notably IoT networks. This paper addresses a fundamental bottleneck of blockchain; the simulation of consensus algorithms. State-of-the-art blockchain consensus algorithm simulators are built on general data that do not consider resource-constrained devices. These simulators have limitations in performance measurement (energy, latency, and throughput) and testing of security attacks, including DoS, Sybil, and 34% or 51% attacks). This paper introduces a blockchain Internet of Things consensus algorithm (BICA) simulator, which offers a framework for testing consensus algorithms with adaptable IoT data in various attack scenarios. It evaluates metrics such as latency, throughput, and attack resilience, providing insights into their capabilities under diverse network conditions. A case study involving Proof of Stake (PoS), Delegated Proof of Stake (DPoS), Proof of Elapse Time (PoET), Proof of Authority (PoA) and Practical Byzantine Fault Tolerance (PBFT) showed PBFT’s superior performance and security against vulnerabilities such as Sybil, DoS, and 34-51% attacks. BICA’s block-creation speed surpasses that of the existing simulators.

The three-tier IoT–Edge–Cloud paradigm enables low-end devices to use the computation capabilities of the more powerful edge nodes to meet efficiency constraints for real-time applications. Many symmetric-key-based schemes rely on an online trusted cloud admin (CA) to establish session keys between IoT devices and edge nodes. In this study, we propose a new provably-secure mutual authentication privacy-preserving protocol with forward secrecy (MAPFS), which eliminates the requirement for an online CA during IoT authentication. To achieve anonymity, our construction utilizes zero-knowledge proofs and randomizes the IoT authentication request. The security of our construction is based on the well-studied discrete logarithm and decisional Diffie–Hellman assumptions in elliptic curve groups. We formally prove that MAPFS ensures mutual authentication and semantic security for session keys. We also evaluate MAPFS performance in terms of the communication overhead, storage requirements, and computation complexity. Finally, we test the performance of MAPFS on a Raspberry Pi 4 and compare it against other certificate-less protocols.

Machine learning is key for automated detection of malicious network activity to ensure that computer networks and organizations are protected against cyber security attacks. Recently, there has been growing interest in the domain of adversarial machine learning, which explores how a machine learning model can be compromised by an adversary, resulting in misclassified output. Whilst to date, most focus has been given to visual domains, the challenge is present in all applications of machine learning where a malicious attacker would want to cause unintended functionality, including cyber security and network traffic analysis. We first present a study on conducting adversarial attacks against a well-trained network traffic classification model. We show how well-crafted adversarial examples can be constructed so that known attack types are misclassified by the model as benign activity. To combat this, we present a novel defensive strategy based on hierarchical learning to help reduce the attack surface that an adversarial example can exploit within the constraints of the parameter space of the intended attack. Our results show that our defensive learning model can withstand crafted adversarial attacks and can achieve classification accuracy in line with our original model when not under attack.

Abstract Group signatures allow members of a group to anonymously sign on behalf of the group. Membership is administered by a designated group manager. The group manager can also reveal the identity of a signer if and when needed to enforce accountability and deter abuse. For group signatures to be applicable in practice, they need to support fully dynamic groups, i.e., users may join and leave at any time. Existing security definitions for fully dynamic group signatures are informal, have shortcomings, and are mutually incompatible. We fill the gap by providing a formal rigorous security model for fully dynamic group signatures. Our model is general and is not tailored toward a specific design paradigm and can therefore, as we show, be used to argue about the security of different existing constructions following different design paradigms. Our definitions are stringent and when possible incorporate protection against maliciously chosen keys. We consider both the case where the group management and tracing signatures are administered by the same authority, i.e., a single group manager, and also the case where those roles are administered by two separate authorities, i.e., a group manager and an opening authority. We also show that a specialization of our model captures existing models for static and partially dynamic schemes. In the process, we identify a subtle gap in the security achieved by group signatures using revocation lists. We show that in such schemes new members achieve a slightly weaker notion of traceability. The flexibility of our security model allows to capture such relaxation of traceability.

Ring signatures and group signatures are prominent cryptographic primitives offering a combination of privacy and authentication. They enable individual users to anonymously sign messages on behalf of a group of users. In ring signatures, the group, i.e. the ring, is chosen in an ad hoc manner by the signer. In group signatures, group membership is controlled by a group manager. Group signatures additionally enforce accountability by providing the group manager with a secret tracing key that can be used to identify the otherwise anonymous signer when needed. Accountable ring signatures, introduced by Xu and Yung (CARDIS 2004), bridge the gap between the two notions. They provide maximal flexibility in choosing the ring, and at the same time maintain accountability by supporting a designated opener that can identify signers when needed. We revisit accountable ring signatures and offer a formal security model for the primitive. Our model offers strong security definitions incorporating protection against maliciously chosen keys and at the same time flexibility both in the choice of the ring and the opener. We give a generic construction using standard tools. We give a highly efficient instantiation of our generic construction in the random oracle model by meticulously combining Camenisch’s group signature scheme (CRYPTO 1997) with a generalization of the one-out-of-many proofs of knowledge by Groth and Kohlweiss (EUROCRYPT 2015). Our instantiation yields signatures of logarithmic size (in the size of the ring) while relying solely on the well-studied decisional Diffie-Hellman assumption. In the process, we offer a number of optimizations for the recent Groth and Kohlweiss one-out-of-many proofs, which may be useful for other applications. Accountable ring signatures imply traditional ring and group signatures. We therefore also obtain highly efficient instantiations of those primitives with signatures shorter than all existing ring signatures as well as existing group signatures relying on standard assumptions.