Cryptography and Security
Privacy-R1: Privacy-Aware Multi-LLM Agent Collaboration via Reinforcement Learning
Zheng Hui, Yijiang River Dong, Sanhanat Sivapiromrat et al. (+2 more)
When users submit queries to Large
Language Models (LLMs), their
prompts can often contain sensitive data, forcing a difficult choice: Send the query to a powerful proprietary LLM providers to achieving state-of-the-art performance and risk data exposure, or relying on smaller, local models guarantees data
privacy but often results in a degradation of task performance. Prior approaches have relied on static pipelines that use LLM rewriting, which shatters linguistic coherence and indiscriminately removes
privacy-sensitive information, including task-critical content. We reformulate this challenge (
Privacy-Conscious Delegation) as a sequential decision-making problem and introduce a novel reinforcement learning (RL) framework called
Privacy-R1 to solve it. Our framework trains an
agent to dynamically route text chunks, learning a policy that optimally balances the trade-off between
privacy leakage and task performance. It implicitly distinguishes between replaceable Personally Identifiable Information (PII) (which it shields locally) and task-critical PII (which it strategically sends to the remote model for maximal utility). To validate our approach in complex scenarios, we also introduce a new medical
dataset with high PII density. Our framework achieves a new state-of-the-art on the
privacy-utility frontier, demonstrating the necessity of learned, adaptive policies for deploying LLMs in sensitive environments.
Dataset can be found at: https://github.com/zackhuiiiii/
Privacy-R1.
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All authors Zheng Hui, Yijiang River Dong, Sanhanat Sivapiromrat, Ehsan Shareghi, Nigel Collier
Cryptography and Security
A Novel GPT-Based Framework for Anomaly Detection in System Logs
Zeng Zhang, Wenjie Yin and Xiaoqi Li
Identification of anomalous events within system logs constitutes a pivotal element within the frame- work of cybersecurity defense strategies. However, this process faces numerous challenges, including the management of substantial data volumes, the distribution of anomalies, and the precision of con- ventional methods. To address this issue, the present paper puts forward a proposal for an intelligent detection method for system logs based on Genera- tive Pre-trained
Transformers (GPT). The efficacy of this approach is attributable to a combination of structured input design and a Focal Loss op- timization strategy, which collectively result in a substantial enhancement of the performance of log anomaly detection. The initial approach involves the conversion of raw logs into event ID sequences through the use of the Drain parser. Subsequently, the Focal Loss loss function is employed to address the issue of class imbalance. The experimental re- sults demonstrate that the optimized GPT-2 model significantly outperforms the unoptimized model in a range of key metrics, including precision, recall, and F1 score. In specific tasks, comparable or superior performance has been demonstrated to that of the GPT-3.5 API.
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Cryptography and Security
Membership Inference over Diffusion-models-based Synthetic Tabular Data
Peini Cheng and Amir Bahmani
This study investigates the
privacy risks associated with
diffusion-based synthetic tabular data generation methods, focusing on their susceptibility to Membership Inference Attacks (MIAs). We examine two recent models, TabDDPM and TabSyn, by developing query-based MIAs based on the step-wise error comparison method. Our findings reveal that TabDDPM is more vulnerable to these attacks. TabSyn exhibits resilience against our attack models. Our work underscores the importance of evaluating the
privacy implications of
diffusion models and encourages further research into robust
privacy-preserving mechanisms for synthetic data generation.
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Cryptography and Security · Cross-listed from cs.LG
RoBCtrl: Attacking GNN-Based Social Bot Detectors via Reinforced Manipulation of Bots Control Interaction
Yingguang Yang, Xianghua Zeng, Qi Wu et al. (+5 more)
Social networks have become a crucial source of real-time information for individuals. The influence of social bots within these platforms has garnered considerable
attention from researchers, leading to the development of numerous detection technologies. However, the vulnerability and robustness of these detection methods is still underexplored. Existing Graph Neural Network (GNN)-based methods cannot be directly applied due to the issues of limited control over social
agents, the black-box nature of bot detectors, and the heterogeneity of bots. To address these challenges, this paper proposes the first
adversarial multi-
agent Reinforcement learning framework for social Bot control attacks (RoBCtrl) targeting GNN-based social bot detectors. Specifically, we use a
diffusion model to generate high-fidelity bot accounts by reconstructing existing account data with minor modifications, thereby evading detection on social platforms. To the best of our knowledge, this is the first application of
diffusion models to mimic the behavior of evolving social bots effectively. We then employ a Multi-
Agent Reinforcement Learning (MARL) method to simulate bots
adversarial behavior. We categorize social accounts based on their influence and budget. Different
agents are then employed to control bot accounts across various categories, optimizing the attachment strategy through reinforcement learning. Additionally, a hierarchical state abstraction based on structural
entropy is designed to accelerate the reinforcement learning. Extensive experiments on social bot detection
datasets demonstrate that our framework can effectively undermine the performance of GNN-based detectors.
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All authors Yingguang Yang, Xianghua Zeng, Qi Wu, Hao Peng, Yutong Xia, Hao Liu, Bin Chong, Philip S. Yu
Cryptography and Security
OCR-APT: Reconstructing APT Stories from Audit Logs using Subgraph Anomaly Detection and LLMs
Ahmed Aly, Essam Mansour and Amr Youssef
Advanced Persistent Threats (APTs) are stealthy cyberattacks that often evade detection in system-level audit logs. Provenance graphs model these logs as connected entities and events, revealing relationships that are missed by linear log representations. Existing systems apply anomaly detection to these graphs but often suffer from high false positive rates and coarse-grained alerts. Their reliance on node attributes like file paths or IPs leads to spurious correlations, reducing detection robustness and reliability. To fully understand an attack's progression and impact, security analysts need systems that can generate accurate, human-like narratives of the entire attack. To address these challenges, we introduce OCR-APT, a system for APT detection and reconstruction of human-like attack stories. OCR-APT uses Graph Neural Networks (GNNs) for subgraph anomaly detection, learning behavior patterns around nodes rather than fragile attributes such as file paths or IPs. This approach leads to a more robust anomaly detection. It then iterates over detected subgraphs using Large
Language Models (LLMs) to reconstruct multi-stage attack stories. Each stage is validated before proceeding, reducing
hallucinations and ensuring an interpretable final report. Our evaluations on the DARPA TC3, OpTC, and NODLINK
datasets show that OCR-APT outperforms state-of-the-art systems in both detection accuracy and alert interpretability. Moreover, OCR-APT reconstructs human-like reports that comprehensively capture the attack story.
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Cryptography and Security
MAGPIE: A benchmark for Multi-AGent contextual PrIvacy Evaluation
Gurusha Juneja, Jayanth Naga Sai Pasupulati, Alon Albalak et al. (+2 more)
A core challenge for autonomous LLM
agents in collaborative settings is balancing robust
privacy understanding and preservation alongside task efficacy. Existing
privacy benchmarks only focus on simplistic, single-turn interactions where private information can be trivially omitted without affecting task outcomes. In this paper, we introduce MAGPIE (Multi-
AGent contextual
PrIvacy Evaluation), a novel
benchmark of 200 high-stakes tasks designed to evaluate
privacy understanding and preservation in multi-
agent collaborative, non-
adversarial scenarios. MAGPIE integrates private information as essential for task resolution, forcing
agents to balance effective collaboration with strategic information control. Our evaluation reveals that state-of-the-art
agents, including GPT-5 and Gemini 2.5-Pro, exhibit significant
privacy leakage, with Gemini 2.5-Pro leaking up to 50.7% and GPT-5 up to 35.1% of the sensitive information even when explicitly instructed not to. Moreover, these
agents struggle to achieve consensus or task completion and often resort to undesirable behaviors such as manipulation and power-seeking (e.g., Gemini 2.5-Pro demonstrating manipulation in 38.2% of the cases). These findings underscore that current LLM
agents lack robust
privacy understanding and are not yet adequately aligned to simultaneously preserve
privacy and maintain effective collaboration in complex environments.
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All authors Gurusha Juneja, Jayanth Naga Sai Pasupulati, Alon Albalak, Wenyue Hua, William Yang Wang
Cryptography and Security · Cross-listed from cs.MM
Game mechanics for cyber-harm awareness in the metaverse
Sophie McKenzie, Jeb Webb and Robin Doss
Educating children and young people to be safe online is essential, especially as the metaverse, a next-generation internet blending immersive technologies, promises to reshape their interactions and amplify their experiences. While virtual reality offers fully immersive, highly interactive, and multi-sensory engagement, it also heightens cyber harm risks for young or vulnerable users. To address this, the CyberNinjas VR experience was developed to educate children aged 8 to 16 on safe metaverse behaviours, providing clear referral steps for harmful interactions. Understanding user engagement in metaverse gaming will aid the design of future VR environments which prioritize safety and inclusivity. This project analyses CyberNinjas to understand how game mechanics can foster cyber-safe behaviours.
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Cryptography and Security
Beyond the Voice: Inertial Sensing of Mouth Motion for High Security Speech Verification
Ynes Ineza, Muhammad A. Ullah, Abdul Serwadda et al. (+1 more)
Voice interfaces are increasingly used in high-stakes domains such as mobile banking, smart-home security, and hands-free healthcare. Meanwhile, modern generative models have made high-quality voice forgeries inexpensive and easy to create, eroding confidence in voice authentication alone. To strengthen protection against such attacks, we present a second authentication factor that combines acoustic evidence with the unique motion patterns of a speaker's lower face. By placing lightweight inertial sensors around the mouth to capture mouth opening and evolving lower-facial geometry, our system records a distinct motion signature with strong discriminative power across individuals. We built a prototype and recruited 43 participants to evaluate the system under four conditions: seated, walking on level ground, walking on stairs, and speaking with different
language backgrounds (native vs. non-native English). Across all scenarios, our approach consistently achieved a median equal-error rate (EER) of 0.01 or lower, indicating that mouth-movement data remain robust under variations in gait, posture, and spoken
language. We discuss specific use cases where this second line of defense could provide tangible security benefits to voice authentication systems.
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All authors Ynes Ineza, Muhammad A. Ullah, Abdul Serwadda, Aurore Munyaneza
Cryptography and Security
Intermittent File Encryption in Ransomware: Measurement, Modeling, and Detection
Ynes Ineza, Gerald Jackson, Prince Niyonkuru et al. (+2 more)
File-encrypting ransomware increasingly employs intermittent encryption techniques, encrypting only parts of files to evade classical detection methods.This paper provides a systematic empirical characterization of byte-level statistics under intermittent encryption across common file types, establishing a baseline for how partial encryption reshapes data structure. Guided by these measurements, we model intermittent encryption as a convex mixture of ciphertext and cleartext and, via a classical KL-divergence bound, derive file-type-specific detectability limits for histogram-based detectors. Leveraging these insights, we evaluate convolutional neural network (CNN) detectors trained on realistic intermittent-encryption configurations from leading ransomware families. Our findings show that localized, chunk-level CNNs consistently outperform whole-file analysis, highlighting a practical, robust baseline for future detection systems.
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All authors Ynes Ineza, Gerald Jackson, Prince Niyonkuru, Jaden Kevil, Abdul Serwadda
Cryptography and Security
AndroByte: LLM-Driven Privacy Analysis through Bytecode Summarization and Dynamic Dataflow Call Graph Generation
Mst Eshita Khatun, Lamine Noureddine, Zhiyong Sui et al. (+1 more)
With the exponential growth in mobile applications, protecting user
privacy has become even more crucial. Android applications are often known for collecting, storing, and sharing sensitive user information such as contacts, location, camera, and microphone data often without the user's clear consent or awareness raising significant
privacy risks and exposure. In the context of
privacy assessment, dataflow analysis is particularly valuable for identifying data usage and potential leaks. Traditionally, this type of analysis has relied on formal methods, heuristics, and rule-based matching. However, these techniques are often complex to implement and prone to errors, such as taint explosion for large programs. Moreover, most existing Android dataflow analysis methods depend heavily on predefined list of sinks, limiting their flexibility and scalability. To address the limitations of these existing techniques, we propose AndroByte, an AI-driven
privacy analysis tool that leverages LLM
reasoning on bytecode summarization to dynamically generate accurate and explainable dataflow call graphs from static code analysis. AndroByte achieves a significant Fe̱ta}-Score of 89% in generating dynamic dataflow call graphs on the fly, outperforming the effectiveness of traditional tools like FlowDroid and Amandroid in leak detection without relying on predefined propagation rules or sink lists. Moreover, AndroByte's iterative bytecode summarization provides comprehensive and explainable insights into dataflow and leak detection, achieving high, quantifiable scores based on the G-Eval metric.
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All authors Mst Eshita Khatun, Lamine Noureddine, Zhiyong Sui, Aisha Ali-Gombe
Cryptography and Security
Partitioning $\mathbb{Z}_{sp}$ in finite fields and groups of trees and cycles
Nikolaos Verykios and Christos Gogos
This paper investigates the algebraic and graphical structure of the ring $\mathbb{Z}_{sp}$, with a focus on its decomposition into finite fields, kernels, and special subsets. We establish classical isomorphisms between $\mathbb{F}_s$ and $p\mathbb{F}_s$, as well as $p\mathbb{F}_s^{\star}$ and $p\mathbb{F}_s^{+1,\star}$. We introduce the notion of arcs and rooted trees to describe the pre-periodic structure of $\mathbb{Z}_{sp}$, and prove that trees rooted at elements not divisible by $s$ or $p$ can be generated from the tree of unity via multiplication by cyclic arcs. Furthermore, we define and analyze the set $\mathbb{D}_{sp}$, consisting of elements that are neither multiples of $s$ or $p$ nor "off-by-one" elements, and show that its graph decomposes into cycles and pre-periodic trees. Finally, we demonstrate that every cycle in $\mathbb{Z}_{sp}$ contains inner cycles that are derived predictably from the cycles of the finite fields $p\mathbb{F}_s$ and $s\mathbb{F}_p$, and we discuss the cryptographic relevance of $\mathbb{D}_{sp}$, highlighting its potential for analyzing cyclic attacks and factorization methods.
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Cryptography and Security
PoTS: Proof-of-Training-Steps for Backdoor Detection in Large Language Models
Issam Seddik, Sami Souihi, Mohamed Tamaazousti et al. (+1 more)
As Large
Language Models (LLMs) gain traction across critical domains, ensuring secure and trustworthy training processes has become a major concern.
Backdoor attacks, where malicious actors inject hidden triggers into training data, are particularly insidious and difficult to detect. Existing post-training verification solutions like Proof-of-Learning are impractical for LLMs due to their requirement for full retraining, lack of robustness against stealthy manipulations, and inability to provide early detection during training. Early detection would significantly reduce computational costs. To address these limitations, we introduce Proof-of-Training Steps, a verification protocol that enables an independent auditor (Alice) to confirm that an LLM developer (Bob) has followed the declared training recipe, including data batches, architecture, and hyperparameters. By analyzing the sensitivity of the LLMs'
language modeling head (LM-Head) to input perturbations, our method can expose subtle
backdoor injections or deviations in training. Even with
backdoor triggers in up to 10 percent of the training data, our protocol significantly reduces the attacker's ability to achieve a high attack success rate (ASR). Our method enables early detection of attacks at the injection step, with verification steps being 3x faster than training steps. Our results highlight the protocol's potential to enhance the accountability and security of LLM development, especially against insider threats.
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All authors Issam Seddik, Sami Souihi, Mohamed Tamaazousti, Sara Tucci Piergiovanni
Cryptography and Security
SMOTE and Mirrors: Exposing Privacy Leakage from Synthetic Minority Oversampling
Georgi Ganev, Reza Nazari, Rees Davison et al. (+5 more)
The Synthetic Minority Over-sampling Technique (SMOTE) is one of the most widely used methods for addressing class imbalance and generating synthetic data. Despite its popularity, little
attention has been paid to its
privacy implications; yet, it is used in the wild in many
privacy-sensitive applications. In this work, we conduct the first systematic study of
privacy leakage in SMOTE: we begin by showing that prevailing evaluation practices, i.e., naive distinguishing and distance-to-closest-record metrics, completely fail to detect any leakage and that membership inference attacks (MIAs) can be instantiated with high accuracy. Then, by exploiting SMOTE's
geometric properties, we build two novel attacks with very limited assumptions: DistinSMOTE, which perfectly distinguishes real from synthetic records in augmented
datasets, and ReconSMOTE, which reconstructs real minority records from synthetic
datasets with perfect precision and recall approaching one under realistic imbalance ratios. We also provide theoretical guarantees for both attacks. Experiments on eight standard imbalanced
datasets confirm the practicality and effectiveness of these attacks. Overall, our work reveals that SMOTE is inherently non-private and disproportionately exposes minority records, highlighting the need to reconsider its use in
privacy-sensitive applications and as a baseline for assessing the
privacy of modern generative models.
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All authors Georgi Ganev, Reza Nazari, Rees Davison, Amir Dizche, Xinmin Wu, Ralph Abbey, Jorge Silva, Emiliano De Cristofaro
Cryptography and Security
Sequential Comics for Jailbreaking Multimodal Large Language Models via Structured Visual Storytelling
Deyue Zhang, Dongdong Yang, Junjie Mu et al. (+6 more)
Multimodal large
language models (MLLMs) exhibit remarkable capabilities but remain susceptible to jailbreak attacks exploiting cross-modal vulnerabilities. In this work, we introduce a novel method that leverages sequential comic-style visual narratives to circumvent safety
alignments in state-of-the-art MLLMs. Our method decomposes malicious queries into visually innocuous storytelling elements using an auxiliary LLM, generates corresponding image sequences through
diffusion models, and exploits the models' reliance on narrative coherence to elicit harmful outputs. Extensive experiments on harmful textual queries from established safety
benchmarks show that our approach achieves an average attack success rate of 83.5%, surpassing prior state-of-the-art by 46%. Compared with existing visual jailbreak methods, our sequential narrative strategy demonstrates superior effectiveness across diverse categories of harmful content. We further analyze attack patterns, uncover key vulnerability factors in
multimodal safety mechanisms, and evaluate the limitations of current defense strategies against narrative-driven attacks, revealing significant gaps in existing protections.
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All authors Deyue Zhang, Dongdong Yang, Junjie Mu, Quancheng Zou, Zonghao Ying, Wenzhuo Xu, Zhao Liu, Xuan Wang, Xiangzheng Zhang
Cryptography and Security
Physical Layer Deception as a Stackelberg Game: Strategy Regimes, Equilibrium, and Robust Design
Wenwen Chen, Bin Han, Yao Zhu et al. (+3 more)
Physical layer deception (PLD) combines physical layer security (PLS) with deception: the transmitter actively misleads the eavesdropper with falsified information. We model the transmitter-eavesdropper interaction as a Stackelberg game in which the transmitter commits to a resource allocation and encryption strategy, and each receiver best-responds by selecting among three decryption modes: Perception, Dropping, and Exclusion. Using semantic distortion as the metric, we derive closed-form switching surfaces that partition the parameter space into strategy regimes and identify conditions under which each regime dominates. The robust operating point, at the peak of the worst-case distortion envelope, is shown to be a Stackelberg
equilibrium; iterative best-response dynamics oscillate around it with strictly lower time-averaged security. We evaluate the design under Nakagami-m fading with static and adaptive transmitter strategies, benchmarked against a classical PLS baseline. Numerical results validate the regime characterization and show 12-55% higher eavesdropper distortion than the erasure-only baseline across all fading conditions.
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All authors Wenwen Chen, Bin Han, Yao Zhu, Anke Schmeink, Giuseppe Caire, Hans D. Schotten
Cryptography and Security
Active Honeypot Guardrail System: Probing and Confirming Multi-Turn LLM Jailbreaks
ChenYu Wu, Yi Wang and Yang Liao
Large
language models (LLMs) are increasingly vulnerable to multi-turn jailbreak attacks, where adversaries iteratively elicit harmful behaviors that bypass single-turn safety filters. Existing defenses predominantly rely on passive rejection, which either fails against adaptive attackers or overly restricts benign users. We propose a honeypot-based proactive guardrail system that transforms risk avoidance into risk utilization. Our framework fine-tunes a bait model to generate ambiguous, non-actionable but semantically relevant responses, which serve as lures to probe user intent. Combined with the protected LLM's safe reply, the system inserts proactive bait questions that gradually expose malicious intent through multi-turn interactions. We further introduce the Honeypot Utility Score (HUS), measuring both the attractiveness and feasibility of bait responses, and use a Defense Efficacy Rate (DER) for balancing safety and usability. Initial experiment on MHJ
Datasets with recent attack method across GPT-4o show that our system significantly disrupts jailbreak success while preserving benign user experience.
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Cryptography and Security
A Hard-Label Black-Box Evasion Attack against ML-based Malicious Traffic Detection Systems
Zixuan Liu, Yi Zhao, Zhuotao Liu et al. (+4 more)
Machine Learning (ML)-based malicious traffic detection is a promising security paradigm. It outperforms rule-based traditional detection by identifying various advanced attacks. However, the robustness of these ML models is largely unexplored, thereby allowing attackers to craft
adversarial traffic examples that evade detection. Existing evasion attacks typically rely on overly restrictive conditions (e.g., encrypted protocols, Tor, or specialized setups), or require detailed prior knowledge of the target (e.g., training data and model parameters), which is impractical in realistic black-box scenarios. The feasibility of a hard-label black-box evasion attack (i.e., applicable across diverse tasks and protocols without internal target insights) thus remains an open challenge. To this end, we develop NetMasquerade, which leverages reinforcement learning (RL) to manipulate attack flows to mimic benign traffic and evade detection. Specifically, we establish a tailored pre-trained model called Traffic-BERT, utilizing a network-specialized tokenizer and an
attention mechanism to extract diverse benign traffic patterns. Subsequently, we integrate Traffic-BERT into the RL framework, allowing NetMasquerade to effectively manipulate malicious packet sequences based on benign traffic patterns with minimal modifications. Experimental results demonstrate that NetMasquerade enables both brute-force and stealthy attacks to evade 6 existing detection methods under 80 attack scenarios, achieving over 96.65% attack success rate. Notably, it can evade the methods that are either empirically or certifiably robust against existing evasion attacks. Finally, NetMasquerade achieves low-latency
adversarial traffic generation, demonstrating its practicality in real-world scenarios.
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All authors Zixuan Liu, Yi Zhao, Zhuotao Liu, Qi Li, Chuanpu Fu, Guangmeng Zhou, Ke Xu
Cryptography and Security · Cross-listed from cs.AI
Mapping Smarter, Not Harder: A Test-Time Reinforcement Learning Agent That Improves Without Labels or Model Updates
Wen-Kwang Tsao, Yao-Ching Yu and Chien-Ming Huang
The Enterprise Intelligence Platform must integrate logs from numerous third-party vendors in order to perform various downstream tasks. However, vendor documentation is often unavailable at test time. It is either misplaced, mismatched, poorly formatted, or incomplete, which makes schema mapping challenging. We introduce a reinforcement learning
agent that can self-improve without labeled examples or model weight updates. During inference, the
agent: 1) Identifies ambiguous field-mapping attempts. 2) Generates targeted web-search queries to gather external evidence. 3) Applies a confidence-based reward to iteratively refine its mappings. To demonstrate this concept, we converted Microsoft Defender for Endpoint logs into a common schema. Our method increased mapping accuracy from 56.4%(LLM-only) to 72.73%(RAG) to 93.94% over 100 iterations using GPT-4o. At the same time, it reduced the number of low-confidence mappings requiring expert review by 85%. This new approach provides an evidence-driven, transparent method for solving future industry problems, paving the way for more robust, accountable, scalable, efficient, flexible, adaptable, and collaborative solutions.
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Cryptography and Security
Secure Sparse Matrix Multiplications and their Applications to Privacy-Preserving Machine Learning
Marc Damie, Florian Hahn, Andreas Peter et al. (+1 more)
To preserve data
privacy, multi-party computation (MPC) enables executing Machine Learning (ML)
algorithms on private data. However, MPC frameworks do not include optimized operations on sparse data. This absence makes them unsuitable for ML applications involving sparse data; e.g., recommender systems or genomics. Even in plaintext, such applications involve high-dimensional sparse data, that cannot be processed without sparsity-related optimizations due to prohibitively large
memory requirements. Since
matrix multiplication is a central building block of ML
algorithms, our work proposes dedicated MPC
algorithms to multiply secret-shared sparse
matrices. Our sparse
algorithms have several advantages over secure dense
matrix multiplications (i.e., the classic multiplication). On the one hand, they avoid the
memory issues caused by the "dense" data representation of dense multiplications. On the other hand, our
algorithms can significantly reduce communication costs (up to $\times1000$) for realistic problem sizes. We validate our
algorithms in two machine learning applications where dense
matrix multiplications are impractical. Finally, we take inspiration from real-world sparse data properties to build 3 techniques minimizing the public knowledge necessary to secure sparse
algorithms.
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All authors Marc Damie, Florian Hahn, Andreas Peter, Jan Ramon
Cryptography and Security · Cross-listed from cs.LG
Provable Unlearning with Gradient Ascent on Two-Layer ReLU Neural Networks
Odelia Melamed, Gilad Yehudai and Gal Vardi
Machine Unlearning aims to remove specific data from trained models, addressing growing
privacy and ethical concerns. We provide a theoretical analysis of a simple and widely used method - gradient ascent - used to reverse the influence of a specific data point without retraining from scratch. Leveraging the implicit bias of gradient descent towards solutions that satisfy the Karush-Kuhn-Tucker (KKT) conditions of a margin maximization problem, we quantify the quality of the unlearned model by evaluating how well it satisfies these conditions w.r.t. the retained data. To formalize this idea, we propose a new success criterion, termed \textbf{$(\epsilon, \delta, \tau)$-successful} unlearning, and show that, for both linear models and two-layer neural networks with high dimensional data, a properly scaled gradient-ascent step satisfies this criterion and yields a model that closely approximates the retrained solution on the retained data. We also show that gradient ascent performs successful unlearning while still preserving generalization in a synthetic Gaussian-mixture setting.
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Cryptography and Security · Cross-listed from cs.AR
ColumnDisturb: Understanding Column-based Read Disturbance in Real DRAM Chips and Implications for Future Systems
İsmail Emir Yüksel, Ataberk Olgun, F. Nisa Bostanc{\i} et al. (+3 more)
We experimentally demonstrate a new widespread read disturbance phenomenon, ColumnDisturb, in real commodity DRAM chips. By repeatedly opening or keeping a DRAM row (aggressor row) open, we show that it is possible to disturb DRAM
cells through a DRAM column (i.e., bitline) and induce bitflips in DRAM
cells sharing the same columns as the aggressor row (across multiple DRAM subarrays). With ColumnDisturb, the activation of a single row concurrently disturbs
cells across as many as three subarrays (e.g., 3072 rows) as opposed to RowHammer/RowPress, which affect only a few neighboring rows of the aggressor row in a single subarray. We rigorously characterize ColumnDisturb and its characteristics under various operational conditions using 216 DDR4 and 4 HBM2 chips from three major manufacturers. Among our 27 key experimental observations, we highlight two major results and their implications. First, ColumnDisturb affects chips from all three major manufacturers and worsens as DRAM technology scales down to smaller node sizes (e.g., the minimum time to induce the first ColumnDisturb bitflip reduces by up to 5.06x). We observe that, in existing DRAM chips, ColumnDisturb induces bitflips within a standard DDR4 refresh window (e.g., in 63.6 ms) in multiple
cells. We predict that, as DRAM technology node size reduces, ColumnDisturb would worsen in future DRAM chips, likely causing many more bitflips in the standard refresh window. Second, ColumnDisturb induces bitflips in many (up to 198x) more rows than retention failures. Therefore, ColumnDisturb has strong implications for retention-aware refresh mechanisms that leverage the heterogeneity in
cell retention times: our detailed analyses show that ColumnDisturb greatly reduces the benefits of such mechanisms.
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All authors İsmail Emir Yüksel, Ataberk Olgun, F. Nisa Bostanc{\i}, Haocong Luo, A. Giray Yağl{\i}kç{\i}, Onur Mutlu