<!doctype html><html lang="en" class="no-js"><head><meta charset="utf-8"> <!-- begin SEO --><title>When Mixnets Fail: Evaluating, Quantifying, and Mitigating the Impact of Adversarial Nodes in Mix Networks - Mahdi Rahimi</title><meta property="og:locale" content="en-US"><meta property="og:site_name" content="Mahdi Rahimi"><meta property="og:title" content="When Mixnets Fail: Evaluating, Quantifying, and Mitigating the Impact of Adversarial Nodes in Mix Networks"><link rel="canonical" href="https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md"><meta property="og:url" content="https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md"><meta property="og:description" name="description" content="Mix networks (mixnets) provide clients with communication anonymity against strong network adversaries by traversing their packets independently through randomly selected hops (mixnodes), which disrupt packet linkability. Although this approach, implemented in Nym, maximizes obfuscation against network adversaries, it enables an adversary who compromises a subset of mixnodes (10%/5% of nodes) to entirely nullify the anonymity of all clients whose communication volume with their destination exceeds a certain threshold (4MB/30MB). To mitigate such vulnerabilities, this work develops a set of novel path selection techniques that achieve a trade-off between resistance to network adversaries and resilience against compromised mixnodes. Observing that existing anonymity metrics are insufficient to quantify adversarial risk in mixnets, we additionally introduce effective empirical and simulation-based metrics. Through theoretical, empirical, and simulation-based evaluations, we comprehensively assess our proposals, demonstrating that the proposed approaches reduce the vulnerability to compromised nodes by up to 80%, while conferring limited advantage to network adversaries. Our analysis further reveals that state-of-the-art anonymity metrics, in contrast to our proposed metrics, produce misleading results that influenced certain design choices in Nym."><meta property="og:type" content="article"><meta property="article:published_time" content="2026-02-27T00:00:00+00:00"> <script type="application/ld+json"> { "@context" : "http://schema.org", "@type" : "Person", "name" : "Mahdi Rahimi", "url" : "https://mmaahhddii1995.github.io", "sameAs" : null } </script> <!-- end SEO --><link href="https://mmaahhddii1995.github.io/feed.xml" type="application/atom+xml" rel="alternate" title="Mahdi Rahimi Feed"> <!-- http://t.co/dKP3o1e --><meta name="HandheldFriendly" content="True"><meta name="MobileOptimized" content="320"><meta name="viewport" content="width=device-width, initial-scale=1.0"> <script> document.documentElement.className = document.documentElement.className.replace(/\bno-js\b/g, '') + ' js '; </script> <!-- For all browsers --><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/main.css"> <!-- Custom CSS to force white background and black text --><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/custom.css"> <!-- Force moon (dark mode) as default on page load --> <script> if (!localStorage.getItem('theme')) { document.documentElement.setAttribute('data-theme', 'light'); localStorage.setItem('theme', 'light'); } </script><meta http-equiv="cleartype" content="on"> <!-- start custom head snippets --> <!-- favicon from https://commons.wikimedia.org/wiki/File:OOjs_UI_icon_academic-progressive.svg --><link rel="apple-touch-icon" sizes="180x180" href="https://mmaahhddii1995.github.io/images/apple-touch-icon-180x180.png"/><link rel="icon" type="image/svg+xml" href="https://mmaahhddii1995.github.io/images/favicon.svg"/><link rel="icon" type="image/png" href="https://mmaahhddii1995.github.io/images/favicon-32x32.png" sizes="32x32"/><link rel="icon" type="image/png" href="https://mmaahhddii1995.github.io/images/favicon-192x192.png" sizes="192x192"/><link rel="manifest" href="https://mmaahhddii1995.github.io/images/manifest.json"/><link rel="icon" href="/images/favicon.ico"/><meta name="theme-color" content="#ffffff"/><link rel="stylesheet" href="https://mmaahhddii1995.github.io/assets/css/academicons.css"/> <!-- Support for MatJax --> <script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js?features=es6"></script> <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script> <!-- end custom head snippets --></head><body> <!--[if lt IE 9]><div class="notice--danger align-center" style="margin: 0;">You are using an <strong>outdated</strong> browser. 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Although this approach, implemented in Nym, maximizes obfuscation against network adversaries, it enables an adversary who compromises a subset of mixnodes (10%/5% of nodes) to entirely nullify the anonymity of all clients whose communication volume with their destination exceeds a certain threshold (4MB/30MB). To mitigate such vulnerabilities, this work develops a set of novel path selection techniques that achieve a trade-off between resistance to network adversaries and resilience against compromised mixnodes. Observing that existing anonymity metrics are insufficient to quantify adversarial risk in mixnets, we additionally introduce effective empirical and simulation-based metrics. Through theoretical, empirical, and simulation-based evaluations, we comprehensively assess our proposals, demonstrating that the proposed approaches reduce the vulnerability to compromised nodes by up to 80%, while conferring limited advantage to network adversaries. Our analysis further reveals that state-of-the-art anonymity metrics, in contrast to our proposed metrics, produce misleading results that influenced certain design choices in Nym."><meta itemprop="datePublished" content="February 27, 2026"><div class="page__inner-wrap"><header><h1 class="page__title" itemprop="headline">When Mixnets Fail: Evaluating, Quantifying, and Mitigating the Impact of Adversarial Nodes in Mix Networks</h1><p>Published in <i>Network and Distributed System Security (NDSS) Symposium</i>, 2026</p></header><section class="page__content" itemprop="text"><p>The contents above will be part of a list of publications, if the user clicks the link for the publication than the contents of section will be rendered as a full page, allowing you to provide more information about the paper for the reader. When publications are displayed as a single page, the contents of the above “citation” field will automatically be included below this section in a smaller font.</p><p style="font-size: smaller">Recommended citation: M. Rahimi "When Mixnets Fail: Evaluating, Quantifying, and Mitigating the Impact of Adversarial Nodes in Mix Networks," in NDSS 2026: 33rd Symposium on Network and Distributed System Security, Internet Society.<br /><a href="http://mmaahhddii1995.github.io/files/WhenMixnetsFail.pdf">Download Paper</a> | <a href="http://mmaahhddii1995.github.io/files/WhenMixnetsFail_bib.bib">Download Bibtex</a></p></section><footer class="page__meta"></footer><section class="page__share"><h4 class="page__share-title">Share on</h4><a href="https://bsky.app/intent/compose?text=https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md" class="btn btn--bluesky" title="Share on Bluesky"><i class="fab fa-bluesky" aria-hidden="true"></i><span> Bluesky</span></a> <a href="https://www.facebook.com/sharer/sharer.php?u=https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md" class="btn btn--facebook" title="Share on Facebook"><i class="fab fa-facebook" aria-hidden="true"></i><span> Facebook</span></a> <a href="https://www.linkedin.com/shareArticle?mini=true&url=https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md" class="btn btn--linkedin" title="Share on LinkedIn"><i class="fab fa-linkedin" aria-hidden="true"></i><span> LinkedIn</span></a> <a href="https://x.com/intent/post?text=https://mmaahhddii1995.github.io/publication/WhenMixnetsFail.md" class="btn btn--x" title="Share on X"><i class="fab fa-x-twitter" aria-hidden="true"></i><span> X (formerly Twitter)</span></a></section><nav class="pagination"> <a href="https://mmaahhddii1995.github.io/publication/OptiMix.md" class="pagination--pager" title="OptiMix: Scalable and Distributed Approaches for Latency Optimization in Modern Mixnets ">Previous</a> <a href="https://mmaahhddii1995.github.io/publication/ICME.md" class="pagination--pager" title="FlowContrast: Few-Shot Multimedia Traffic Representation Learning in LEO Satellite Networks ">Next</a></nav></div></article></div><div class="page__footer"><footer> <!-- Sitemap & follow removed --> <!-- Footer removed --></footer></div><script src="https://mmaahhddii1995.github.io/assets/js/main.min.js"></script></body></html>
