Author: Denis Avetisyan
A new analysis pits reinforcement learning algorithms against a barrage of threats targeting blockchain-based Internet of Things networks.

The study compares Reinforcement Learning, Deep Reinforcement Learning, and Multi-Agent Reinforcement Learning strategies against Naive, Collusive, Adaptive, Byzantine, and Time-Delayed Poisoning attacks in Blockchain IoT environments.
Despite growing adoption, securing blockchain-enabled Internet of Things networks remains challenging due to sophisticated adversarial threats targeting trust mechanisms. This paper, ‘Adaptive Trust Consensus for Blockchain IoT: Comparing RL, DRL, and MARL Against Naive, Collusive, Adaptive, Byzantine, and Sleeper Attacks’, systematically evaluates the performance of reinforcement learning-including tabular, deep, and multi-agent approaches-against a diverse range of attacks from simple malicious behavior to coordinated poisoning. Our findings demonstrate that while deep learning enhances detection capabilities, particularly against collusive attacks, all evaluated agents remain critically vulnerable to subtle, long-term ‘time-delayed poisoning’ attacks initiated by patient adversaries. Can truly robust trust consensus be achieved in these environments, or are blockchain IoT systems inherently susceptible to insidious, delayed compromise?
Decentralized Trust: The Foundation of Resilient IoT Networks
Conventional Internet of Things networks often rely on centralized architectures, where data streams converge on a limited number of servers for processing and control. This approach, while seemingly efficient, introduces critical vulnerabilities; a compromise of these central servers can disrupt the entire network, creating a single point of failure. Furthermore, the concentration of sensitive data makes these systems attractive targets for malicious actors and raises significant privacy concerns for users. Every device’s information must transit through this central hub, creating opportunities for interception, manipulation, and unauthorized access. Consequently, the security and reliability of the entire IoT ecosystem are fundamentally tied to the protection of these few, crucial nodes – a precarious dependency in an increasingly interconnected world.
The inherent limitations of scaling traditional Internet of Things networks stem from a core dependency on centralized verification processes. Each device interaction and data transmission requires confirmation from a central authority, creating bottlenecks as network size increases and response times lengthen. This centralized model also proves vulnerable to malicious actors; a compromised central server can disrupt the entire system or manipulate data undetected. Effectively addressing these threats necessitates constant monitoring and security updates, further straining resources and hindering scalability. Unlike systems designed for limited growth, expansive IoT deployments require a more resilient architecture capable of autonomously verifying transactions and isolating malicious activity without relying on a single, vulnerable point of control.
The future of the Internet of Things hinges on a fundamental shift away from centralized trust models. Current systems, reliant on single authorities for verification, struggle with scalability and present attractive targets for attack, jeopardizing both data integrity and user privacy. Decentralized trust mechanisms, leveraging technologies like blockchain and distributed ledger technologies, offer a compelling alternative by distributing validation across the network. This approach not only eliminates single points of failure but also enhances resilience against malicious activity, as compromising a single node yields limited impact. By enabling devices to independently verify data and transactions, decentralized systems promise a more secure, scalable, and ultimately, more reliable IoT ecosystem capable of supporting the exponential growth of connected devices and the increasingly sensitive data they generate.

Dynamic Consensus: Observing Trust in Action
The network employs a Trust-Based Consensus mechanism where node reliability is not pre-defined but continuously assessed. This process involves monitoring node behavior – specifically, the accuracy and consistency of data reported or actions performed – and adjusting a trust score accordingly. Unlike traditional consensus algorithms that assume a fixed set of trustworthy participants, this system dynamically adapts to observed performance, effectively isolating or penalizing nodes exhibiting unreliable or malicious behavior. The trust scores are then used to weight the influence of each node during the consensus process, ensuring that more reliable nodes have a proportionally greater impact on the final agreed-upon state of the network.
The network’s consensus mechanism continuously adjusts node weights based on real-time performance. Nodes demonstrating consistent, accurate data transmission and participation in validation processes receive increased weight, effectively enhancing their influence in future consensus rounds. Conversely, nodes exhibiting behaviors such as data falsification, consistent unavailability, or attempts to disrupt network operations experience a reduction in weight. This penalty diminishes their impact on consensus and can ultimately lead to exclusion from critical network functions. The magnitude of both rewards and penalties is determined by a pre-defined sensitivity factor and the severity of the observed behavior, ensuring a responsive and adaptive system that prioritizes reliable participation.
The Bayesian Trust Model assigns each node a trustworthiness score represented as a probability distribution. This distribution is updated iteratively based on observed interactions and reported behavior. Initially, all nodes begin with a neutral prior probability. As nodes participate in consensus rounds and provide data, the model incorporates evidence – successful validations increase the probability, while failures or inconsistencies decrease it. The update process utilizes Bayes’ Theorem to calculate a posterior probability, effectively weighting prior beliefs against new evidence. Specifically, P(Trustworthy | Evidence) = \frac{P(Evidence | Trustworthy) * P(Trustworthy)}{P(Evidence)}, where P(Trustworthy) represents the prior belief, P(Evidence | Trustworthy) is the likelihood of observing the evidence if the node is trustworthy, and P(Evidence) is the normalizing constant. This probabilistic assessment allows the system to differentiate between temporary errors and malicious behavior, adapting the consensus weight assigned to each node accordingly.

Optimized Delegate Selection: Balancing Exploration and Exploitation
Thompson Sampling is employed as a probabilistic delegate selection mechanism to optimize consensus efficiency and security. This approach maintains a probability distribution representing the trustworthiness of each node in the network. During delegate selection, nodes are sampled from this distribution; nodes with higher assessed trustworthiness have a correspondingly higher probability of selection. This balances exploration – selecting potentially trustworthy but unverified nodes to gather more data – with exploitation – preferentially selecting known reliable nodes to expedite consensus. The algorithm dynamically updates these probability distributions based on observed delegate behavior, increasing the assessed trustworthiness of consistently honest nodes and decreasing that of nodes exhibiting malicious or unreliable behavior. This adaptive process ensures the system continually refines its delegate selection strategy, mitigating the risk of relying on compromised nodes while maximizing overall consensus performance.
Evaluation of delegate selection strategies under collusive attack scenarios indicates that a Multi-Agent Reinforcement Learning (MARL) approach achieves a significantly higher F1-score of 0.85. This performance represents an improvement over both Deep Reinforcement Learning (DRL), which yielded an F1-score of 0.68, and traditional Reinforcement Learning (RL), which achieved an F1-score of 0.50. The F1-score, calculated as the harmonic mean of precision and recall, provides a combined metric for evaluating the ability of each approach to accurately identify and exclude colluding malicious delegates from the consensus process.
The delegate selection process employs a sampling methodology designed to mitigate the impact of potentially malicious nodes on consensus. By probabilistically choosing delegates, the system reduces reliance on any single node and diversifies the decision-making process. This approach inherently limits the influence of compromised delegates, as their votes are not guaranteed to be included in each consensus round. Simultaneously, the sampling strategy prioritizes delegates with established positive reputations, ensuring that reliable nodes contribute frequently and maintain the efficiency of the consensus mechanism. The balance between exploring new delegates and exploiting known reliable ones optimizes both security and performance within the distributed system.
Evaluation against Byzantine Fault Injection attacks demonstrated a consistent and perfect detection rate across all agent types – Reinforcement Learning (RL), Deep Reinforcement Learning (DRL), and Multi-Agent Reinforcement Learning (MARL) – each achieving an F1-score of 1.00. This indicates that all three approaches are equally capable of identifying and mitigating the effects of malicious nodes deliberately injecting false or misleading information into the system, ensuring data integrity and system reliability under adversarial conditions.

Enhanced Security and Privacy: FHE-Secured ABAC for Data Confidentiality
The system leverages Fully Homomorphic Encryption (FHE) to revolutionize data access control within the Blockchain IoT network. Traditionally, evaluating access control policies requires decrypting sensitive data, creating a significant vulnerability. However, this architecture incorporates FHE-Secured Attribute-Based Access Control (ABAC), allowing policy evaluation directly on encrypted data without prior decryption. This innovative approach ensures that data remains confidential throughout the entire process, safeguarding privacy while still enabling fine-grained authorization. By performing computations on ciphertext, the system eliminates the need to expose plaintext data, effectively mitigating the risks associated with data breaches and unauthorized access – a critical advancement for secure IoT deployments.
The system architecture prioritizes data security through a unique combination of encryption and access control mechanisms. By leveraging Fully Homomorphic Encryption (FHE), sensitive data remains encrypted even during processing and policy evaluation, effectively shielding it from unauthorized access. This innovative approach allows for fine-grained access control, ensuring that only authorized parties can decrypt and utilize specific data elements. The result is a robust framework where data confidentiality is maintained without compromising the ability to enforce granular permissions, offering a significant advancement in data governance and security for interconnected systems.
The system’s security architecture extends beyond static access controls through the implementation of Reinforcement Learning, enabling dynamic trust delegation based on observed network behavior. This adaptive approach allows the system to respond to evolving threat landscapes and bolster overall resilience; however, testing revealed a vulnerability to Time-Delayed Poisoning attacks, where malicious data introduced over time significantly degraded performance, resulting in all agents achieving a low F1-score between 0.11 and 0.16 under such conditions. Notably, the system demonstrated robust defenses against more immediate threats, achieving perfect detection – an F1-score of 1.00 – against both Naive Malicious Attacks and Adaptive Adversarial Attacks, highlighting a nuanced security profile where proactive, rapid-response defenses are strong, but long-term, subtly introduced corruption presents a considerable challenge.
The system’s resilience against malicious activity is notably strong, as demonstrated by its perfect detection rate – achieving an F1-score of 1.00 – when facing both naive and adaptive adversarial attacks. This indicates the effectiveness of the implemented Deep Reinforcement Learning (DRL) and Multi-Agent Reinforcement Learning (MARL) strategies in discerning malicious behavior, even as attackers attempt to circumvent security measures through increasingly sophisticated techniques. The flawless detection signifies a robust defense capable of maintaining system integrity and safeguarding data against a spectrum of threats, highlighting the potential of these learning-based approaches for proactive security in complex network environments.

The study meticulously dissects the vulnerabilities inherent in blockchain IoT networks, revealing a concerning susceptibility to time-delayed poisoning attacks despite advancements in reinforcement learning. This echoes a sentiment articulated by John McCarthy: “The best way to predict the future is to invent it.” The research doesn’t simply identify weaknesses; it actively probes potential solutions – RL, DRL, and MARL – attempting to invent a more resilient future for these systems. However, the persistence of vulnerabilities under sustained, patient attacks highlights the complexity of securing distributed networks, demonstrating that even sophisticated algorithms are not immune to subtle, long-term manipulation. The focus on adaptive trust, while promising, underscores the need for continued refinement and proactive defense strategies against increasingly cunning adversaries.
Where Do We Go From Here?
The pursuit of trust, even computationally, proves predictably circuitous. This work demonstrates that layered complexity – in this case, increasingly sophisticated reinforcement learning algorithms – offers diminishing returns against an adversary possessing a simple, yet patient, strategy. The ‘sleeper attack,’ or time-delayed poisoning, reveals a fundamental asymmetry: defense necessitates constant vigilance, while attack requires only occasional, carefully placed disruption. The problem isn’t a lack of intelligence in the defensive systems, but an excess of assumptions about the attacker’s timeframe.
Future effort should not focus on anticipating how attacks will occur, but on minimizing their impact when they inevitably do. A shift toward resilient, rather than preventative, architectures seems warranted. Consider systems designed to rapidly identify and isolate compromised nodes, rather than attempting to predict malicious behavior. The elegance lies not in foresight, but in graceful recovery.
Ultimately, the question isn’t whether a blockchain IoT network can be made perfectly secure – a futile pursuit – but whether it can be made sufficiently robust. The goal is not to eliminate risk, but to render it inconsequential. Simplicity, it appears, remains the most potent defense.
Original article: https://arxiv.org/pdf/2512.22860.pdf
Contact the author: https://www.linkedin.com/in/avetisyan/
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2025-12-31 06:05