FINDING · DETECTION
Under DoH/3, EDNS(0) padding and HTTP/3 framing collapse packet-length diversity: more than 99% of request packets fall within 233–350 bytes and more than 99% of response packets fall within 555–777 bytes. Direction-signed length-sequence classifiers (RF, LSTM, CNN) achieve only 67.39%, 8.95%, and 7.43% accuracy respectively on 449 classes — near or below random — confirming that size-based traffic analysis features lose nearly all discriminative power against DoH/3.
From 2026-zhang-dohfuse-dual-branch-architecture — DoHFuse: A Dual-Branch Architecture with DMAGLSTM for Website Fingerprinting over DNS over HTTPS/3 · §IV.D; §V.B; Table I · 2026 · arXiv preprint
Implications
- Circumvention transports that route through DoH/3 gain meaningful size-obfuscation for free from EDNS(0) padding; adopting DoH/3 as an inner-tunnel framing neutralizes the most common passive-classifier attack surface.
- Tool designers should not assume that size-homogenizing padding prevents fingerprinting — adversaries will pivot to timing features, so complementary inter-packet interval jitter is still required.
Tags
Extracted by claude-sonnet-4-6 — review before relying.