While stream multiplexing reduces the visibility of encapsulated TLS handshakes by
merging inner connections, the paper cautions that multiplexing plus random padding
alone is "inherently limited" as a long-term countermeasure. Censors can adapt by
monitoring burst sizes and round-trip counts at the outer-connection level, which
remain correlated with the number of inner TLS sessions regardless of padding.
From 2024-xue-fingerprinting — Fingerprinting Obfuscated Proxy Traffic with Encapsulated TLS Handshakes
· §7 (Limitations and Future Work)
· 2024
· USENIX Security Symposium
Implications
Multiplexing must be combined with active burst shaping (deliberate inter-packet delays and size normalization) to prevent the outer connection's timing pattern from leaking the inner TLS session count.
REALITY and TLS-forwarding approaches that make the outer handshake indistinguishable from a real TLS server still expose inner-handshake structure once the censor can observe full-stream patterns; complete replacement of inner TLS with non-TLS app-layer framing would be required to fully close this vector.