Cryptography and Security
One-Prompt Censorship Evasion via Generative Diffusion Models
Shiyi Ling, Yuhang Gan and Chen Qian
The escalating arms race between Internet censorship and evasion has driven censors to evolve from static rule-based filtering to sophisticated deep learning-based traffic analysis. While recent automated evasion tools have attempted to counter this by leveraging
stochastic search and programmable heuristics, they continue to suffer from insufficient evasion robustness across diverse censorship modalities and poor usability due to complex, mechanism-specific configurations that require manual fitness tuning or domain-specific
languages. In this paper, we propose a paradigm shift that reframes censorship evasion as a semantic image-to-image editing task, allowing users to execute it with a single
prompt. We introduce FlowPaint, a novel generative framework that leverages the "world knowledge" of large
diffusion models to automatically reshape censored traffic into benign patterns. FlowPaint utilizes an instruction-tuned
diffusion architecture to perform semantic editing on network flows. Evaluations against both industrial-grade rule-based middleboxes and learning-based classifiers demonstrate that FlowPaint outperforms existing censorship evasion baselines, enabling users to counter diverse censorship paradigms solely by varying natural
language instructions
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Cryptography and Security
VeriPort: Automated and Verified Patch Backporting at Scale
Jonah Ghebremichael, Wenxin Jiang, Mikola Lysenko et al. (+3 more)
One of the key challenges for securing the software supply chain is addressing known vulnerabilities in third-party open-source dependencies. Security patches are frequently only available for the latest version of a dependency, leaving developers with the choice of either upgrading to the latest version (risking breaking changes) or manually backporting the security fix. Prior work backports to a single version that must be specified in advance and does not produce sufficient evidence to demonstrate that their patches block exploitation and preserve functionality. In this paper, we present VeriPort, an end-to-end agentic system that scalably backports a patch for a given vulnerability advisory to every affected version of the package. For each backport, VeriPort builds a chain of evidence to confirm that the patch blocks exploitation and preserves intended behavior. VeriPort reliably resolves 95.3% of 128 backporting tasks in BackportBench, outperforming the best existing solution (Claude Code) by 22.7 percentage points. We further deployed VeriPort on 169 high- and critical-severity CVEs and have generated over 5,000 verified backported patches. Moreover, VeriPort's value extends beyond simply backporting patches. It uncovered 2,100 versions incorrectly reported as affected and 127 previously unidentified vulnerable versions across 92 advisories, and 23 advisories have since been corrected upstream by removing 387 versions and adding 81.
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All authors Jonah Ghebremichael, Wenxin Jiang, Mikola Lysenko, Benjamin Barslev Nielsen, William Enck, Alexandros Kapravelos
Cryptography and Security · Cross-listed from cs.LG
SCRUB-FL: Sanitizing and Cleansing Representations via Unlearning of Backdoors
Osama Wehbi, Sarhad Arisdakessian, Omar Abdel Wahab et al. (+2 more)
Federated Learning (FL) enables collaborative model training without sharing raw data, making it a promising paradigm for
privacy-sensitive applications. However, its decentralized nature makes it inherently vulnerable to
backdoor attacks, where malicious clients embed hidden triggers into local training data to manipulate model predictions. Existing defenses mainly operate during before and during aggregation cannot fully eliminate
backdoor behaviors that persist in the converged global model. Moreover, the effectiveness of post-training sanitization is often limited by the server's lack of knowledge of trigger patterns or poisoned clients after convergence, resulting in residual
backdoor behaviors or accuracy degradation due to
neuron entanglement. To address this limitation, we propose SCRUB-FL (Sanitizing and Cleansing Representations via Unlearning of
Backdoors), a two-phase solution for post-training
backdoor removal in FL. During training, clients identify suspicious samples using spectral analysis and activation clustering, then train lightweight Wasserstein Generative
Adversarial Network with Gradient Penalty (WGAN-GP) models to capture trigger-related distributions. The generator parameters are aggregated server-side to construct a global representation of suspicious patterns without exposing raw data. After convergence, the server synthesizes trigger-approximating samples and applies machine unlearning to erase the trigger-target association by redistributing predictions toward a uniform distribution. Experimental evaluations on CIFAR-10 and GTSRB across three attack types and up to 40% malicious participation demonstrate that SCRUB-FL reduces the
backdoor attack success rate to as low as 3.88% while maintaining over 91% normal task accuracy, outperforming state-of-the-art defenses without requiring prior trigger knowledge or a large clean proxy
dataset at the server.
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All authors Osama Wehbi, Sarhad Arisdakessian, Omar Abdel Wahab, Azzam Mourad, Hadi Otrok
Cryptography and Security
Black-Box Forensics for Conversational LLM Agents
Isadora White, Yasaman Jafari and Taylor Berg-Kirkpatrick
As LLM-powered scams proliferate, black-box forensics for conversational LLM
agents offers a path to accountability for systems hidden behind anonymous endpoints. Identifying the base model behind a chatbot endpoint (attribution), without model parameter access or knowledge of the hidden system
prompt, would let investigators trace AI-enabled scams back to the providers whose models power them. Detecting when two endpoints run the exact same system
prompt (fingerprinting), even one novel and unseen, would link individual scams into criminal networks and expose silent API changes. We conduct an empirical investigation of both capabilities. Our attribution classifiers identify the base model behind an
agent with 98% accuracy from a few turns of non-
adversarial conversation. Attribution of system
prompts, while possible, requires retraining on a large amount of data for each
prompt; system
prompts in the wild are unbounded and ever-changing, making this approach costly. To tackle this more open-ended setting, our cross-encoder fingerprinting method achieves an AUC of 0.768 and an F1 of 0.703 on entirely unseen system
prompts, and aggregating 50 interaction conversations from each target
agent boosts AUC to 0.943. Conversational
agents with unseen system
prompts can thus be fingerprinted with robust accuracy from a few turns of ordinary conversation.
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Cryptography and Security
The Geometry of Refusal: Linear Instability in Safety-Aligned LLMs
Shivam Ratnakar and Kartikeya Vats
Modern Large
Language Models (LLMs) rely on extensive safety
alignment, yet the mechanistic basis of refusal remains opaque. In this work, we investigate whether safety compliance is a deep semantic decision or a manipulable linear feature. We introduce Contrastive Logit Steering (CLS), a zero-optimization framework that isolates the "refusal direction" by contrasting hidden states derived from safe and unrestricted system
prompts. Unlike representation engineering methods that intervene on internal activations, CLS operates directly on the output distribution, serving as a diagnostic probe for
alignment fragility. When coupled with prefix injection to bypass initial refusal reflexes, this method induces a phase transition where guardrails collapse. Our experiments on 7 model families reveal that safety implementation is architecturally deterministic. While models like Llama-3.1 exhibit a "Late Decision"
topology that is easily bypassed by CLS (reaching 95% ASR in approximately one second), others like Qwen-2.5 demonstrate "Early Divergence" by integrating safety mid-computation. Direct comparison with established activation-level steering methods shows that CLS achieves substantially higher attack success rates on Llama 2 (73% vs. 22.6%) and Qwen 7B (91% vs. 79.2%), demonstrating that logit-level intervention exposes
alignment vulnerabilities that hidden-state methods underestimate. Beyond attacks, we show that this linearity enables bidirectional control: inverting the steering vector "hardens" models against jailbreaks without retraining. Our findings suggest that current
alignment techniques create a steerable "safety axis" that serves as both a critical vulnerability and a precise primitive for defense.
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Cryptography and Security
Confidently Wrong: Severity-Aware Calibration of Prompt-Injection Detectors under Attack Shift
Md Anas Biswas
Prompt-injection detectors are deployed as guards: a model scores an input and a downstream system trusts or blocks it on that score. I study the confidence of these scores, not only their accuracy, when the attack distribution shifts away from the clean
benchmark on which the operating point was chosen. I evaluate three released detectors, ProtectAI-v2 and two
Prompt-Guard-2 checkpoints, at a single source-calibrated threshold that I freeze and transport across five shifts. I report a severity metric S, how confident a detector is on the attacks it misses, alongside the false-negative rate and discrimination. Across every shift and every detector, severity on the missed attacks stays between 0.99 and 1.00 while the false-negative rate ranges from 0.01 to 0.97: when these detectors miss, they miss with near-certainty. All three confidently pass indirect behavior-hijack injection, a blind spot unanimous across two vendors and a fourfold size range. Standard pooled calibration error does not register this; one detector it rates well-calibrated, at 0.06, is miscalibrated at 0.91 on the attacks alone. Run against live models, the missed injections leak the majority of working exploits, passing them at the rate they catch others. A controlled experiment traces the cause to content-keying rather than injection structure, an instruction-tuned model used as a judge shows the same hijack blind spot, and a black-box rewriter exploits the content-keying to manufacture working confident misses, most effectively on the most dangerous attack category. Code and data are public.
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Cryptography and Security
RAVEN: Agentic RAG for Automated Vulnerability Repair
Varun Gadey, Zijie Liu and Alexandra Dmitrienko
Automated vulnerability repair has emerged as a promising direction to mitigate the growing number of software vulnerabilities. Recent advances in Large
Language Models (LLMs) have further accelerated research in automated repair. However, existing frameworks remain largely restricted to
memory-related vulnerabilities and locally repairable vulnerability settings, leaving generalization to unseen vulnerability types underexplored. Their evaluations are often limited to a single programming
language, and largely rely on proprietary models. In this paper, we propose RAVEN, a scalable, efficient and autonomous framework that integrates an agentic
retrieval-augmented generation (RAG) pipeline with controlled iterative repair in a unified framework. The framework utilizes open-source LLMs in a fully locally deployable setting with limited GPU requirements, while building a multi-faceted
retrieval pipeline to retrieve historically relevant vulnerability fixes and guide the patch generation. In addition, RAVEN introduces a dedicated Curator
Agent that retrieves cross-file dependencies from the target repository, to fix complex vulnerabilities that cannot be addressed using local vulnerable code alone. We evaluate RAVEN on 160 real-world CVE vulnerabilities across diverse vulnerability types, two programming
languages, unseen CWE categories, and out-of-distribution settings. RAVEN achieves an overall repair success rate of 83.13%, outperforming all existing state-of-the-art repair frameworks, while also demonstrating strong generalization capabilities and maintaining the repair cost negligible.
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Cryptography and Security
ColumnKeeper: Efficient Solutions to the ColumnDisturb Vulnerability in DRAM-based Systems
Andreas Kosmas Kakolyris, F. Nisa Bostanci, Ataberk Olgun et al. (+7 more)
Modern DRAM chips are vulnerable to read disturbance phenomena such as RowHammer and RowPress, which induce bitflips after accessing nearby rows a certain number of times (the read disturbance threshold). ColumnDisturb is a new, fundamentally different DRAM read disturbance phenomenon. Specifically, ColumnDisturb (i) disturbs DRAM columns instead of rows, and (ii) increases the number of affected DRAM
cells from those in only a few neighboring rows to all
cells across three consecutive DRAM subarrays. We propose ColumnKeeper, the first set of ColumnDisturb mitigations, in two variants: ColumnKeeper-D (CK-D), a deterministic mechanism, and ColumnKeeper-P (CK-P), a probabilistic one. CK-D exploits DRAM's open-bitline architecture to provide deterministic security guarantees at low performance and energy overheads: it uses two counters per subarray to track activations affecting the odd and even columns, and refreshes one row in a subarray when either counter reaches a predetermined threshold. CK-P instead refreshes one row in three consecutive subarrays upon a row activation in the middle subarray, with a predetermined probability, providing configurable security guarantees at low area overhead. Both mechanisms prevent ColumnDisturb bitflips at low performance, energy, and area overheads. At the current experimentally-demonstrated ColumnDisturb threshold (1M), CK-D and CK-P incur very low average single-core performance overheads of 0.15% and 0.36%, respectively. For near-future thresholds (128K), these rise to a still low average of 1.70% and 2.73%. Mitigating ColumnDisturb at low thresholds (e.g., 16K) remains possible by adopting smaller subarray sizes or enabling subarray-level parallelism. CK-D and CK-P require low area overheads of 0.1 mm^2 and 0.03 mm^2, respectively. ColumnKeeper is freely available at https://github.com/CMU-SAFARI/ColumnKeeper .
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All authors Andreas Kosmas Kakolyris, F. Nisa Bostanci, Ataberk Olgun, Ismail Emir Yuksel, Harsh Songara, Konstantinos Marios Sgouras, Umut Baser, Konstantinos Kanellopoulos, A. Giray Yaglikci, Onur Mutlu
Cryptography and Security · Cross-listed from cs.SE
On Good Authority: Release-Authority Measurement for Registry-Mediated Package Ecosystems
Igor Santos-Grueiro
Dependency graphs reveal where released code can flow; release-authority records reveal how a release reached users. A package can keep the same downstream exposure while its public authority path changes: a new publisher account, a repository relink, a new workflow, a provenance change, a signing-key movement, or a shift in publication mediation. These transitions expose a release-time review surface over public control-plane evidence, before payload evidence or incident attribution is available. We introduce a predecessor-aware release-authority record that compares each package release with its immediate predecessor across publisher, repository, workflow, provenance, signing, and mediation evidence. We apply the record to a purposefully sampled, audited April 2024-June 2026 cohort from npm, PyPI, Maven Central, crates.io, and RubyGems: 45,812 releases, 43,100 eligible predecessor comparisons, and 942 package coordinates. We report Go separately as a VCS/proxy/checksum-log boundary adapter. Transparent rules identify 204 public release-path discontinuities and define a 204-release candidate review queue. A uniform semantic-distance rule selects 320 releases and covers 190/204 triggers; a descriptive regime-specific rule selects 337 releases and covers all 204. Practitioner review supports the operational reading of this queue. In a blinded 60-row shared core, three practitioners rated 20/30 triggers as immediate review, 9/30 as monitoring, 1/30 as no review, and all 30 controls as no review. External
alignment defines the boundary of the surface: exact malicious versions have zero overlap with policy triggers in our cohort. Compromises that reuse the same public release path, unchanged compromised CI, and versions absent from public snapshots require separate evidence beyond this release-authority record.
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Cryptography and Security · Cross-listed from cs.AR
Non-Uniform L2 Cache Latency Across the Streaming Multiprocessors of an NVIDIA L40
Faruk Alpay and Baris Basaran
The NVIDIA L40 exposes a 96 MiB L2 cache usually modeled as one uniform pool with a single hit latency. We show this is wrong at the granularity a kernel sees: L2-hit latency depends strongly and reproducibly on which physical streaming multiprocessor (SM) issues the load. A turn-serialized, %smid-resolved probe maps the hit latency across all 142 SMs in one launch; it is not a constant near 279 cycles but spans 222-339 cycles (a 52% range), with per-repetition noise below 0.01 cycles. An additive model $L = \mu + a(\mathrm{sm}) + b(\mathrm{slice})$ explains $R^2 = 0.87$ (0.98 with one rank-1 term), and the SM term is two-fold symmetric (two halves of 72 SMs at correlation $r = 0.999$), following the AD102 GPC layout. Independent access patterns agree per SM at $r = 1.000$, so the effect is physical. The same probe on a Blackwell RTX 5090 shows it generalizes, while the per-die pattern is device-specific. Read as a fingerprint, a single user-level probe identifies the SM within a device at 92%, and two physically identical L40s are separated at 100% despite near-identical mean latency (per-SM map $r = 0.63$): a per-die hardware identity, not a clock artifact. This is a self-localization and fingerprinting primitive: a kernel reads its own placement and device, not a victim's, and extracts no secret data. The map is stable, unchanged after an hour at full utilization on both devices. As a consequence, distributing latency-bound work by the map cuts makespan by up to 11%. Single-thread capacity, line-tag, prefetch-modifier, and persisting-L2 results appear as controls. The artifact contains seeds, raw observations, the trained model, and regeneration scripts.
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Cryptography and Security
From CVE to CWE: Syscall-Based HIDS Generalisation
Alexander V. Kozachok, Stanislav G. Vyugov and Shamil G. Magomedov
Host intrusion detection systems (HIDS) based on system-call traces are typically trained and evaluated against individual Common Vulnerabilities and Exposures (CVE) instances. In operational settings, however, defenders need to recognise new exploits of an already known type of weakness. We empirically examine whether a one-class anomaly detector trained on the normal behaviour of a set of CVEs that share a Common Weakness Enumeration (CWE) class generalises to a different, unseen CVE inside the same class. Using six scenarios drawn from LID-DS-2021 and grouped into three CWE families (CWE-307 broken authentication, CWE-89 SQL injection, CWE-434 unrestricted file upload), we extract a 66-dimensional Peng-Guo-style feature vector per sliding window and train Isolation Forest and SGD One-Class SVM detectors with normal-only thresholds calibrated to fixed target false positive rates. We define and answer four research questions covering self-detection, asymmetric cross-CVE transfer, the value of a combined CWE-level normal profile, and the effect of feature filtering on transferability. The combined CWE-307 detector reaches F1 = 0.6976 at calibration target FPR = 0.05 (precision = 0.8994, recall = 0.5698), whereas CWE-89 and CWE-434 collapse to F1 <= 0.21 under the same protocol. Cross-CVE transfer turns out to be strongly direction-dependent and dominated by the breadth of the source normal profile rather than by the CWE label. We conclude that CWE-level generalisation in HIDS is empirically attainable for some but not all weakness families with current syscall features, and we argue that calibrated FPR is a methodological prerequisite for honest reporting in this setting.
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Cryptography and Security
Evidence-Bound Gateway-Path Provenance for Third-Party LLM Inference
Fei Wang and Zebai Tian
Third-party LLM gateways select providers, models, endpoints, and fallback paths while also authoring the records used to explain and bill those decisions. We present evidence-bound gateway-path provenance, which makes these decisions subject to client-verifiable request contracts. An attested mediation runtime intersects a signed service policy with the client's authorization, constructs provider-facing calls, and protects streamed responses. The contract distinguishes initial routes from fallback destinations and admits each transition only after an authorized failure. A signed close-out binds the execution trace, provider-reported usage, authorized pricing, and complete response. We formalize the protocol state machine and establish authorization preservation, execution and stream binding, charge integrity, and channel confidentiality relative to the public receipt metadata. The analysis also characterizes replay, runtime replacement, and the information disclosed by public payload commitments. Controlled software-path measurements show 0.442 ms paired p95 latency overhead at concurrency one, peak throughput of 10.65 thousand requests/s, and stream close-out below 0.4 ms p95. An AWS Nitro Enclaves prototype completed 30 live single-route streaming requests with attestation-bound session and signing keys. The design separates gateway administration from payload processing and supplies a verifiable account of each confirmed execution.
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Cryptography and Security
Detecting and Understanding Vulnerabilities in Fully Homomorphic Encryption Frameworks
Yiteng Peng, Dongwei Xiao, Zhibo Liu et al. (+2 more)
Fully homomorphic encryption (FHE) allows computations to be performed directly on encrypted data without decryption, offering strong
privacy guarantees for sensitive data analysis. This capability is important for
privacy-sensitive applications like secure cloud computing, finance, and healthcare. The complexity of FHE schemes, however, has hindered their practical adoption. To make FHE accessible to a broader range of developers, a new generation of specialized frameworks has emerged to translate high-level FHE programs into complex FHE operations, introducing a new programming paradigm. However, the inherent complexity of FHE frameworks makes them prone to incorrect implementation logic. Unlike mere crashes, logic bugs in these frameworks can silently corrupt encrypted computation, potentially leading to severe financial losses and security vulnerabilities in FHE-enhanced applications. In this work, we introduce HERTA, the first automated testing tool tailored for FHE frameworks. HERTA leverages metamorphic testing to uncover deep-seated implementation bugs and vulnerabilities across the multi-layered FHE software stack. To that end, we design a set of novel metamorphic relations (MRs) derived specifically from FHE semantics. These MRs stress the most challenging aspects of the pipeline, enabling automated correctness testing without the need for a manual ground truth. Our evaluation of HERTA on 3 leading industry frameworks discovered 21 previously unknown bugs, several of which have already been confirmed and fixed by developers. Furthermore, our hazard analysis reveals the critical security impact these bugs pose to the integrity and availability of FHE-based services.
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All authors Yiteng Peng, Dongwei Xiao, Zhibo Liu, Zhenlan JI, Shuai Wang