Cryptography and Security
Robust Federated Learning for Malicious Clients using Loss Trend Deviation Detection
Deepthy K Bhaskar, Minimol B and Binu V P
Federated Learning (FL) facilitates collaborative model training among distributed clients while ensuring that raw data remains on local devices.Despite this advantage, FL systems are still exposed to risks from malicious or unreliable participants. Such clients can interfere with the training process by sending misleading updates, which can negatively affect the performance and reliability of the global model. Many existing defense mechanisms rely on gradient inspection, complex similarity computations, or cryptographic operations, which introduce additional overhead and may become unstable under non-IID data distributions. In this paper, we propose the
Federated Learning with Loss Trend Detection (FL-LTD), a lightweight and
privacy-preserving defense framework that detects and mitigates malicious behavior by monitoring temporal loss dynamics rather than model gradients. The proposed approach identifies anomalous clients by detecting abnormal loss stagnation or abrupt loss fluctuations across communication rounds. To counter adaptive attackers, a short-term
memory mechanism is incorporated to sustain mitigation for clients previously flagged as anomalous, while enabling trust recovery for stable participants. We evaluate FL-LTD on a non-IID
federated MNIST setup under loss manipulation attacks. Experimental results demonstrate that the proposed method significantly enhances robustness, achieving a final test accuracy of 0.84, compared to 0.41 for standard FedAvg under attack. FL-LTD incurs negligible computational and communication overhead, maintains stable convergence, and avoids client exclusion or access to sensitive data, highlighting the effectiveness of loss-based monitoring for secure
federated learning.
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Cryptography and Security
ICON: Intent-Context Coupling for Efficient Multi-Turn Jailbreak Attack
Xingwei Lin, Wenhao Lin, Sicong Cao et al. (+4 more)
Multi-turn jailbreak attacks have emerged as a critical threat to Large
Language Models (LLMs), bypassing safety mechanisms by progressively constructing
adversarial contexts from scratch and incrementally refining
prompts. However, existing methods suffer from the inefficiency of incremental context construction that requires step-by-step LLM interaction, and often stagnate in suboptimal regions due to surface-level optimization. In this paper, we characterize the Intent-Context Coupling phenomenon, revealing that LLM safety constraints are significantly relaxed when a malicious intent is coupled with a semantically congruent context pattern. Driven by this insight, we propose ICON, an automated multi-turn jailbreak framework that efficiently constructs an authoritative-style context via prior-guided semantic routing. Specifically, ICON first routes the malicious intent to a congruent context pattern (e.g., Scientific Research) and instantiates it into an attack
prompt sequence. This sequence progressively builds the authoritative-style context and ultimately elicits prohibited content. In addition, ICON incorporates a Hierarchical Optimization Strategy that combines local
prompt refinement with global context switching, preventing the attack from stagnating in ineffective contexts. Experimental results across eight SOTA LLMs demonstrate the effectiveness of ICON, achieving a state-of-the-art average Attack Success Rate (ASR) of 97.1%. Code is available at https://github.com/xwlin-roy/ICON.
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All authors Xingwei Lin, Wenhao Lin, Sicong Cao, Jiahao Yu, Renke Huang, Lei Xue, Chunming Wu
Cryptography and Security
Towards Sensitivity-Aware Language Models
Dren Fazlija, Iyiola E. Olatunji, Daniel Kudenko et al. (+1 more)
With LLMs increasingly deployed in corporate data management, it is crucial to ensure that these models do not leak sensitive information. In the context of corporate data management, the concept of sensitivity awareness has been introduced, enabling LLMs to adhere to predefined access rights rules. However, it remains unclear how sensitivity awareness relates to established notions of
privacy, such as differential
privacy (DP), thereby making it difficult to deploy meaningfully in real-world applications. In this work, we formalize the notion of sensitivity awareness and theoretically establish its connection to DP. Additionally, we develop a supervised fine-tuning recipe to make existing, four-bit quantized LLMs more sensitivity-aware. With a performance boost of up to 21.7%, the finetuned LLMs not only substantially improve over their baseline but also outperform other full-precision open-source and commercial models of similar size in achieving sensitivity awareness, demonstrating the effectiveness of our proposed approach. At the same time, our method also largely preserves the models' performance on other tasks, such as general instruction-following, mathematical, and common-sense
reasoning.
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All authors Dren Fazlija, Iyiola E. Olatunji, Daniel Kudenko, Sandipan Sikdar
Cryptography and Security
Decentralized Identity in Practice: Benchmarking Latency, Cost, and Privacy
Abylay Satybaldy, Kamil Tylinski and Jiahua Xu
Decentralized Identifiers (DIDs) are increasingly deployed on distributed ledgers, yet systematic cross-platform evidence on their operational behavior remains limited. We present an empirical benchmarking study of three prominent ledger-based DID methods - Ethereum, Hedera, and XRP Ledger - using reference Software Development Kits (SDKs) under a unified experimental setup. We measure latency, transaction cost, and on-chain metadata exposure, normalizing latency by each platform's block or consensus interval and cost by its native value transfer fee.
Privacy leakage is quantified using a Metadata-Leakage Score (MLS), an
entropy-based measure expressed in bits per operation. Our results reveal distinct architectural trade-offs. Ethereum enables near-instant, off-chain DID creation, but incurs the highest latency and cost for on-chain lifecycle operations. XRPL delivers deterministic and stable latency with fixed, low fees, yet exhibits higher metadata leakage due to more verbose transaction payloads. Hedera achieves the lowest on-chain latency and low fees with minimal metadata leakage, while occasional variance arises from SDK-side processing and confirmation pipelines. Overall, the findings show that ledger architecture and SDK workflows play a major role in shaping DID latency, cost, and metadata exposure, complementing the effects of the underlying consensus mechanism. These results provide evidence-based insights to support informed selection and configuration of DID systems under performance and
privacy constraints.
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Cryptography and Security
Supply Chain Insecurity: Exposing Vulnerabilities in iOS Dependency Management Systems
David Schmidt, Sebastian Schrittwieser and Edgar Weippl
Dependency management systems are a critical component in software development, enabling projects to incorporate existing functionality efficiently. However, misconfigurations and malicious actors in these systems pose severe security risks, leading to supply chain attacks. Despite the widespread use of smartphone apps, the security of dependency management systems in the iOS software supply chain has received limited
attention. In this paper, we focus on CocoaPods, one of the most widely used dependency management systems for iOS app development, but also examine the security of Carthage and Swift Package Manager (SwiftPM). We demonstrate that iOS apps expose internal package names and versions. Attackers can exploit this leakage to register previously unclaimed dependencies in CocoaPods, enabling remote code execution (RCE) on developer machines and build servers. Additionally, we show that attackers can compromise dependencies by reclaiming abandoned domains and GitHub URLs. Analyzing a
dataset of 9,212 apps, we quantify how many apps are susceptible to these vulnerabilities. Further, we inspect the use of vulnerable dependencies within public GitHub repositories. Our findings reveal that popular apps disclose internal dependency information, enabling dependency confusion attacks. Furthermore, we show that hijacking a single CocoaPod library through an abandoned domain could compromise 63 iOS apps, affecting millions of users. Finally, we compare iOS dependency management systems with Cargo, Go modules, Maven, npm, and pip to discuss mitigation strategies for the identified threats.
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Cryptography and Security
/dev/SDB: Software Defined Boot – A novel standard for diskless booting anywhere and everywhere
Aditya Mitra, Hamza Haroon, Amaan Rais Shah et al. (+3 more)
A computer is nothing but a device that processes the instructions supplied to it. However, as computers evolved, the instructions or codes started to be more complicated. As computers started to be used by non-technical people, it became imperative that the users be able to use the machine without having underlying knowledge of the code or the hardware. And operating system became the backbone for translating the inputs from the user to actual operation on the hardware. With the increasing complexity and the choices of operating system, it became clear that different groups of people, especially in an enterprise scenario, required different operating systems. Installing them all on a single machine, for shared computers became a difficult task, giving rise to network-based booting. But network-based booting was confined to only wired connectivity, keeping it restricted to very small geographical areas. The proposed system, /dev/SDB, is aimed at creating a standard where any user, anyone on the globe, can access the operating system authorized to them without having to be on the corporate network. It aims to offer the same over Wi-Fi as well as cellular connectivity, ensuring employees can truly work from anywhere, while following the policies for operating systems and without redundant hardware.
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All authors Aditya Mitra, Hamza Haroon, Amaan Rais Shah, Mohammad Elham Rasooli, Bogdan Itsam Dorantes Nikolaev, Tuğçe Ball{\i}
Cryptography and Security
IoT Device Identification with Machine Learning: Common Pitfalls and Best Practices
Kahraman Kostas and Rabia Yasa Kostas
This paper critically examines the device identification process using machine learning, addressing common pitfalls in existing literature. We analyze the trade-offs between identification methods (unique vs. class based), data heterogeneity, feature extraction challenges, and evaluation metrics. By highlighting specific errors, such as improper data augmentation and misleading session identifiers, we provide a robust guideline for researchers to enhance the reproducibility and generalizability of IoT security models.
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Cryptography and Security
TÄMU: Emulating Trusted Applications at the (GlobalPlatform)-API Layer
Philipp Mao, Li Shi, Marcel Busch et al. (+1 more)
Mobile devices rely on Trusted Execution Environments (TEEs) to execute security-critical code and protect sensitive assets. This security-critical code is modularized in components known as Trusted Applications (TAs). Vulnerabilities in TAs can compromise the TEE and, thus, the entire system. However, the closed-source nature and fragmentation of mobile TEEs severely hinder dynamic analysis of TAs, limiting testing efforts to mostly static analyses. This paper presents TÄMU, a rehosting platform enabling dynamic analysis of TAs, specifically fuzzing and debugging, by interposing their execution at the API layer. To scale to many TAs across different TEEs, TÄMU leverages the standardization of TEE APIs, driven by the GlobalPlatform specifications. For the remaining TEE-specific APIs not shared across different TEEs, TÄMU introduces the notion of greedy high-level emulation, a technique that allows prioritizing manual rehosting efforts based on the potential coverage gain during fuzzing. We implement TÄMU and use it to emulate 67 TAs across four TEEs. Our fuzzing campaigns yielded 17 zero-day vulnerabilities across 11 TAs. These results indicate a deficit of dynamic analysis capabilities across the TEE ecosystem, where not even vendors with source code unlocked these capabilities for themselves. TÄMU promises to close this gap by bringing effective and practical dynamic analysis to the mobile TEE domain.
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All authors Philipp Mao, Li Shi, Marcel Busch, Mathias Payer
Cryptography and Security
Fuzzy Private Set Union via Oblivious Key Homomorphic Encryption Retrieval
Jean-Guillaume Dumas, Aude Maignan and Luiza Soezima
Private Set Multi-Party Computations are protocols that allow parties to jointly and securely compute functions: apart from what is deducible from the output of the function, the input sets are kept private. Then, a Private Set Union (PSU), resp. Intersection (PSI), is a protocol that allows parties to jointly compute the union, resp. the intersection, between their private sets. Now a structured PSI, is a PSI where some structure of the sets can allow for more efficient protocols. For instance in Fuzzy PSI, elements only need to be close enough, instead of equal, to be part of the intersection. We present in this paper, Fuzzy PSU protocols (FPSU), able to efficiently take into account approximations in the union. For this, we introduce a new efficient sub-protocol, called Oblivious Key Homomorphic Encryption
Retrieval (OKHER), improving on Oblivious Key-Value
Retrieval (OKVR) techniques in our setting. In the fuzzy context, the receiver set $X=\{x_i\}_{1..n}$ is replaced by ${\mathcal B}_\delta (X)$, the union of $n$ balls of dimension $d$ with radius $\delta$, centered at the $x_i$. The sender set is just its $m$ points of dimension $d$. Then the FPSU functionality corresponds to $X \sqcup \{y \in Y, y \notin {\mathcal B}_\delta (X)\}$. Thus, we formally define the FPSU functionality and security properties, and propose several protocols tuned to the patterns of the balls using the $l_\infty$ distance. Using our OKHER routine and homomorphic encryption, we are for instance able to obtain a FPSU protocols with an asymptotic communication volume bound ranging from $O(dm\log(\delta{n}))$ to $O(d^2m\log(\delta^2n))$, depending on the receiver data set structure.
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Cryptography and Security
Towards Quantum-Safe O-RAN – Experimental Evaluation of ML-KEM-Based IPsec on the E2 Interface
Mario Perera, Michael Mackay, Max Hashem Eiza et al. (+3 more)
As Open
Radio Access Network (O-RAN) deployments expand and adversaries adopt 'store-now, decrypt-later' strategies, operators need empirical data on the cost of migrating critical control interfaces to post-
quantum cryptography (PQC). This paper experimentally evaluates the impact of integrating a NIST-aligned module-
lattice KEM (ML-KEM,
CRYSTALS-Kyber) into IKEv2/IPsec protecting the E2 interface between the 5G Node B (gNB) and the Near-Real-Time RAN Intelligent Controller (Near-RT RIC). Using an open-source testbed built from srsRAN, Open5GS, FlexRIC and strongSwan (with liboqs), we compare three configurations: no IPsec, classical ECDH-based IPsec, and ML-KEM-based IPsec. The study focuses on IPsec tunnel-setup latency and the runtime behaviour of Near-RT RIC xApps under realistic signalling workloads. Results from repeated, automated runs show that ML-KEM integration adds a small overhead to tunnel establishment, which is approximately 3~5 ms in comparison to classical IPsec, while xApp operation and RIC control loops remain stable in our experiments. These findings indicate that ML-KEM based IPsec on the E2 interface is practically feasible and inform
quantum-safe migration strategies for O-RAN deployments.
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All authors Mario Perera, Michael Mackay, Max Hashem Eiza, Alessandro Raschellà, Nathan Shone, Mukesh Kumar Maheshwari
Cryptography and Security
A High-Performance Fractal Encryption Framework and Modern Innovations for Secure Image Transmission
Sura Khalid Salsal, Eman Shaker Mahmood, Farah Tawfiq Abdul Hussien et al. (+3 more)
The current digital era, driven by growing threats to data security, requires a robust image encryption technique. Classical encryption
algorithms suffer from a trade-off among security, image fidelity, and computational efficiency. This paper aims to enhance the performance and efficiency of image encryption. This is done by proposing Fractal encryption based on
Fourier transforms as a new method of image encryption, leveraging state-of-the-art technology. The new approach considered here intends to enhance both security and efficiency in image encryption by comparing Fractal Encryption with basic methods. The suggested system also aims to optimise encryption/ decryption times and preserve image quality. This paper provides an introduction to Image Encryption using the fractal-based method, its mathematical formulation, and its comparative efficiency against publicly known traditional encryption methods. As a result, after filling the gaps identified in previous research, it has significantly improved both its encryption/decryption time and image fidelity compared to other techniques. In this paper, directions for future research and possible improvements are outlined for
attention.
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All authors Sura Khalid Salsal, Eman Shaker Mahmood, Farah Tawfiq Abdul Hussien, Maryam Mahdi Alhusseini, Azhar Naji Alyahya, Nikolai Safiullin
Cryptography and Security
LIFT: Byzantine Resilient Hub-Sampling
Mohamed Amine Legheraba, Nour Rachdi, Maria Gradinariu Potop-Butucaru et al. (+1 more)
Recently, a novel peer sampling protocol, Elevator, was introduced to construct network
topologies tailored for emerging decentralized applications such as
federated learning and blockchain. Elevator builds hub-based
topologies in a fully decentralized manner, randomly selecting hubs among participating nodes. These hubs, acting as central nodes connected to the entire network, can be leveraged to accelerate message dissemination. Simulation results have shown that Elevator converges rapidly (within 3–4 cycles) and exhibits robustness against crash failures and churn. However, its resilience to Byzantine adversaries has not been investigated. In this work, we provide the first evaluation of Elevator under Byzantine adversaries and show that even a small fraction (2%) of Byzantine nodes is sufficient to subvert the network. As a result, we introduce LIFT, a new protocol that extends Elevator by employing a cryptographically secure pseudo-random number generator (PRNG) for hub selection, thereby mitigating Byzantine manipulation. In contrast, LIFT withstands
adversarial infiltration and remains robust with up to 10% Byzantine nodes. These results highlight the necessity of secure randomness in decentralized hub formation and position LIFT as a more reliable building block for Byzantine-resilient decentralized systems.
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All authors Mohamed Amine Legheraba, Nour Rachdi, Maria Gradinariu Potop-Butucaru, Sébastien Tixeuil
Cryptography and Security
Multimodal Multi-Agent Ransomware Analysis Using AutoGen
Asifullah Khan, Aimen Wadood, Mubashar Iqbal et al. (+1 more)
Ransomware has become one of the most serious cybersecurity threats causing major financial losses and operational disruptions worldwide.Traditional detection methods such as static analysis, heuristic scanning and behavioral analysis often fall short when used alone. To address these limitations, this paper presents
multimodal multi
agent ransomware analysis framework designed for ransomware classification. Proposed
multimodal multiagent architecture combines information from static, dynamic and network sources. Each data type is handled by specialized
agent that uses auto encoder based feature extraction. These representations are then integrated through a fusion
agent. After that fused representation are used by
transformer based classifier. It identifies the specific ransomware family. The
agents interact through an interagent feedback mechanism that iteratively refines feature representations by suppressing low confidence information. The framework was evaluated on large scale
datasets containing thousands of ransomware and benign samples. Multiple experiments were conducted on ransomware
dataset. It outperforms single modality and nonadaptive fusion baseline achieving improvement of up to 0.936 in Macro-F1 for family classification and reducing calibration error. Over 100 epochs, the agentic feedback loop displays a stable monotonic convergence leading to over +0.75 absolute improvement in terms of
agent quality and a final composite score of around 0.88 without fine tuning of the
language models. Zeroday ransomware detection remains family dependent on polymorphism and modality disruptions. Confidence aware abstention enables reliable real world deployment by favoring conservativeand trustworthy decisions over forced classification. The findings indicate that proposed approach provides a practical andeffective path toward improving real world ransomware defense systems.
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All authors Asifullah Khan, Aimen Wadood, Mubashar Iqbal, Umme Zahoora
Cryptography and Security
UnlearnShield: Shielding Forgotten Privacy against Unlearning Inversion
Lulu Xue, Shengshan Hu, Wei Lu et al. (+6 more)
Machine unlearning is an emerging technique that aims to remove the influence of specific data from trained models, thereby enhancing
privacy protection. However, recent research has uncovered critical
privacy vulnerabilities, showing that adversaries can exploit unlearning inversion to reconstruct data that was intended to be erased. Despite the severity of this threat, dedicated defenses remain lacking. To address this gap, we propose UnlearnShield, the first defense specifically tailored to counter unlearning inversion. UnlearnShield introduces directional perturbations in the cosine representation space and regulates them through a constraint module to jointly preserve model accuracy and forgetting efficacy, thereby reducing inversion risk while maintaining utility. Experiments demonstrate that it achieves a good trade-off among
privacy protection, accuracy, and forgetting.
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All authors Lulu Xue, Shengshan Hu, Wei Lu, Ziqi Zhou, Yufei Song, Jianhong Cheng, Minghui Li, Yanjun Zhang, Leo Yu Zhang
Cryptography and Security
SemBind: Binding Diffusion Watermarks to Semantics Against Black-Box Forgery Attacks
Xin Zhang, Zijin Yang, Kejiang Chen et al. (+3 more)
Latent-based watermarks, integrated into the generation process of latent
diffusion models (LDMs), simplify detection and attribution of generated images. However, recent black-box forgery attacks, where an attacker needs at least one watermarked image and black-box access to the provider's model, can embed the provider's watermark into images not produced by the provider, posing outsized risk to provenance and trust. We propose SemBind, the first defense framework for latent-based watermarks that resists black-box forgery by binding latent signals to image semantics via a learned semantic masker. Trained with contrastive learning, the masker yields near-invariant codes for the same
prompt and near-orthogonal codes across
prompts; these codes are reshaped and permuted to modulate the target latent before any standard latent-based watermark. SemBind is generally compatible with existing latent-based watermarking schemes and keeps image quality essentially unchanged, while a simple mask-ratio parameter offers a tunable trade-off between anti-forgery strength and robustness. Across four mainstream latent-based watermark methods, our SemBind-enabled anti-forgery variants markedly reduce false acceptance under black-box forgery while providing a controllable robustness-security balance.
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All authors Xin Zhang, Zijin Yang, Kejiang Chen, Linfeng Ma, Weiming Zhang, Nenghai Yu
Cryptography and Security
Eliciting Least-to-Most Reasoning for Phishing URL Detection
Holly Trikilis, Pasindu Marasinghe, Fariza Rashid et al. (+1 more)
Phishing continues to be one of the most prevalent attack vectors, making accurate classification of phishing URLs essential. Recently, large
language models (LLMs) have demonstrated promising results in phishing URL detection. However, their
reasoning capabilities that enabled such performance remain underexplored. To this end, in this paper, we propose a Least-to-Most prompting framework for phishing URL detection. In particular, we introduce an "answer sensitivity" mechanism that guides Least-to-Most's iterative approach to enhance
reasoning and yield higher prediction accuracy. We evaluate our framework using three URL
datasets and four state-of-the-art LLMs, comparing against a one-shot approach and a supervised model. We demonstrate that our framework outperforms the one-shot baseline while achieving performance comparable to that of the supervised model, despite requiring significantly less training data. Furthermore, our in-depth analysis highlights how the iterative
reasoning enabled by Least-to-Most, and reinforced by our answer sensitivity mechanism, drives these performance gains. Overall, we show that this simple yet powerful prompting strategy consistently outperforms both one-shot and supervised approaches, despite requiring minimal training or few-shot guidance. Our experimental setup can be found in our Github repository github.sydney.edu.au/htri0928/least-to-most-phishing-detection.
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All authors Holly Trikilis, Pasindu Marasinghe, Fariza Rashid, Suranga Seneviratne
Cryptography and Security
Securing AI Agents in Cyber-Physical Systems: A Survey of Environmental Interactions, Deepfake Threats, and Defenses
Mohsen Hatami, Van Tuan Pham, Hozefa Lakadawala et al. (+1 more)
The increasing integration of AI
agents into cyber-physical systems (CPS) introduces new security risks that extend beyond traditional cyber or physical threat models. Recent advances in generative AI enable deepfake and semantic manipulation attacks that can compromise
agent perception,
reasoning, and interaction with the physical environment, while emerging protocols such as the Model Context Protocol (MCP) further expand the attack surface through dynamic tool use and cross-domain context sharing. This survey provides a comprehensive review of security threats targeting AI
agents in CPS, with a particular focus on environmental interactions, deepfake-driven attacks, and MCP-mediated vulnerabilities. We organize the literature using the SENTINEL framework, a lifecycle-aware methodology that integrates threat characterization, feasibility analysis under CPS constraints, defense selection, and continuous validation. Through an end-to-end case study grounded in a real-world smart grid deployment, we quantitatively illustrate how timing, noise, and false-positive costs constrain deployable defenses, and why detection mechanisms alone are insufficient as decision authorities in safety-critical CPS. The survey highlights the role of provenance- and physics-grounded trust mechanisms and defense-in-depth architectures, and outlines open challenges toward trustworthy AI-enabled CPS.
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All authors Mohsen Hatami, Van Tuan Pham, Hozefa Lakadawala, Yu Chen
Cryptography and Security
Reference-Free Spectral Analysis of EM Side-Channels for Always-on Hardware Trojan Detection
Mahsa Tahghigh and Hassan Salmani
Always-on hardware Trojans (HTs) pose a critical risk to trusted microelectronics, yet most side-channel detection methods rely on unavailable golden references. We present a reference-free approach that combines time-frequency EM analysis with Gaussian Mixture Models (GMMs). By applying Short-Time
Fourier Transform (STFT) at multiple window sizes, we show that HT-free
circuits exhibit fluctuating statistical structure, while always-on HTs leave persistent footprints with fewer, more consistent mixture components. Results on AES-128 demonstrate feasibility without requiring reference models.
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