--- title: ML-KEM vs Diffie-Hellman: The Showdown – IPsec Series,... description: A detailed comparison of X25519 (Diffie-Hellman) and ML-KEM-768 across four dimensions: wire size, latency, compute cost, and security. ML-KEM keys are 25–50×... canonical: https://daily.dev/posts/ml-kem-vs-diffie-hellman-the-showdown-ipsec-series-part-3-hyqdbip5i twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: ML-KEM vs Diffie-Hellman: The Showdown – IPsec Series, Part 3 | daily.dev og:description: A detailed comparison of X25519 (Diffie-Hellman) and ML-KEM-768 across four dimensions: wire size, latency, compute cost, and security. ML-KEM keys are 25–50×... og:url: https://daily.dev/posts/ml-kem-vs-diffie-hellman-the-showdown-ipsec-series-part-3-hyqdbip5i og:image: https://api.daily.dev/og/posts/hyqDBip5I.png og:image:alt: ML-KEM vs Diffie-Hellman: The Showdown – IPsec Series, Part 3 og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # ML-KEM vs Diffie-Hellman: The Showdown – IPsec Series, Part 3 **[Cisco](https://daily.dev/sources/cisco)** · 5 min read · 0 upvotes · 0 comments ## Summary A detailed comparison of X25519 (Diffie-Hellman) and ML-KEM-768 across four dimensions: wire size, latency, compute cost, and security. ML-KEM keys are 25–50× larger than X25519, forcing IKE fragmentation, but its lattice operations are surprisingly fast — comparable to or faster than elliptic-curve math. The security trade-off is clear: X25519 is battle-tested but quantum-vulnerable, while ML-KEM is quantum-safe but newly standardized (FIPS 203, 2024). The recommended solution is a hybrid key exchange via RFC 9370, which runs both algorithms in a single IKEv2 handshake and combines their shared secrets. An attacker must break both simultaneously. The cost is one extra round trip and ~2 KB per handshake. The strongSwan config string `x25519-ke1_mlkem768` implements this pattern, with X25519 in IKE_SA_INIT and ML-KEM in IKE_INTERMEDIATE. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Watch a Hybrid Post-Quantum Handshake on the Wire – IPsec Series, Part 4](https://daily.dev/posts/watch-a-hybrid-post-quantum-handshake-on-the-wire-ipsec-series-part-4-rpovq4vpj) · Cisco · 0 upvotes · 0 comments - [ML-KEM Mythbusting](https://daily.dev/posts/ml-kem-mythbusting-vzzrjb5k5) · Lobsters · 0 upvotes · 0 comments - [Standardizing Post-Quantum IPsec: Cloudflare Adopts Hybrid ML-KEM to Replace Ciphersuite Bloat](https://daily.dev/posts/standardizing-post-quantum-ipsec-cloudflare-adopts-hybrid-ml-kem-to-replace-ciphersuite-bloat-72husfcdu) · InfoQ · 0 upvotes · 0 comments - [Harvest Now, Decrypt Later: The Threat to Key Exchange – Quantum Series, Part 2](https://daily.dev/posts/harvest-now-decrypt-later-the-threat-to-key-exchange-quantum-series-part-2-eadei5fjg) · Cisco · 0 upvotes · 0 comments - [Mutual Post-Quantum Auth over IKEv2 – IPsec Series, Part 8](https://daily.dev/posts/mutual-post-quantum-auth-over-ikev2-ipsec-series-part-8-xm1etcoxb) · Cisco · 1 upvotes · 0 comments --- Tags: [#quantum-computing](https://daily.dev/tags/quantum-computing) [View this post on daily.dev](https://daily.dev/posts/ml-kem-vs-diffie-hellman-the-showdown-ipsec-series-part-3-hyqdbip5i) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"ML-KEM vs Diffie-Hellman: The Showdown – IPsec Series, Part 3","url":"https://daily.dev/posts/ml-kem-vs-diffie-hellman-the-showdown-ipsec-series-part-3-hyqdbip5i","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/ml-kem-vs-diffie-hellman-the-showdown-ipsec-series-part-3-hyqdbip5i"},"datePublished":"2026-07-20T14:04:05.287Z","dateModified":"2026-07-20T14:04:32.454Z","description":"A detailed comparison of X25519 (Diffie-Hellman) and ML-KEM-768 across four dimensions: wire size, latency, compute cost, and security. 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