hack-house/docs/stage-07-paper-draft.md

Consent-Gated Federated Onion Routing: Linkability and Anonymity-Set Effects of an In-Band Accept/Reject Relay Model

Draft — SS4 lead paper (G4 + RQ1 + RQ2). DATA-INDEPENDENT SECTIONS ONLY.

Blinding status (prereg §2, binding). This draft was written while the confirmatory battery was still running and before any confirmatory intermediate result was inspected. All Results / Discussion content is therefore held as empty placeholders and will be filled once, after the full battery completes and the raw outputs are sealed (stage-05 immutability). The frozen prereg (sor-consent-prereg.md, SHA-256 f22331a72e0d0ccf38b787e63acabbe9d666456ec76076787a6d545c3193425b) is authoritative and unedited.

RQ2 caveat (hard hold). The RQ2 dependent variable — a per-circuit adversary sender posterior — has a construction gap the frozen prereg leaves open (see docs/stage-05-rq2-posterior-clarification.md, PROPOSED, operator-ratification pending). No RQ2 confirmatory statistic is computed, inspected, or reported in this draft. RQ2 methods text below is hedged accordingly; RQ2 result content stays empty until the posterior construction is ratified AND the battery completes.

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Abstract (skeleton — quantitative claims held until data + RQ2 ratification)

Onion-routing systems typically admit any relay that meets a directory's technical criteria; they do not model relay consent — a host's in-band, per-circuit choice to carry a given flow. We build and measure a consent-gated, federated, nested-SSH relay data plane in which every hop must explicitly accept or reject each circuit through a signed in-band handshake (Ed25519-authenticated, X25519 per-hop credentials), and in which relays are organized into houses that federate either through a shared bridge or through a directory. Treating this as a measurement instrument for a trust model's exposure (not a service that provides anonymity), we ask two confirmatory questions on a lab grid of two phones and a laptop: (RQ1) does a shared bridge introduce a measurable flow-linkability leak between a circuit's entry and exit segments, and does cover padding remove it; (RQ2) does federating relays across houses grow or shrink the anonymity set an adversary faces, and is any effect explained by bridge-concentration funnelling. All detectors are frozen and calibrated on known-linked/known-unlinked and equiprobable-sender fixtures before any confirmatory cell is run; all inference is bootstrap-based with BCa 95% CIs, Holm–Bonferroni-corrected across the confirmatory family. [RESULTS — HELD BLIND.]

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1. Introduction

Anonymous-communication systems from onion routing [Reed1997; Dingledine2004] to its SSH-based descendant SOR [Egners2012] share a membership model that is essentially permissionless at the relay: a node participates if it meets directory or protocol criteria, and the routing layer does not represent whether a host consents to carry a particular circuit. Yet in social-trust and friend-to-friend designs — Freenet [Clarke2000], membership-concealing overlays [Vasserman2009], and social-graph routers such as Pisces [Mittal2012] and X-Vine [Mittal2012b] — who is willing to relay for whom is a first-class property. No existing system, to our knowledge, makes per-circuit relay consent an in-band, cryptographically-authenticated protocol step and then measures the privacy consequences of that gate. That gap — an accept/reject relay model whose linkability and anonymity-set behaviour are empirically characterised — is the novelty this work targets (G4).

We do not propose consent-gating as a deployed anonymity service. We build it as a defensive-measurement instrument: a controlled data plane whose knobs (bridge on/off, cover padding, federation topology) let us measure how a consent gate reshapes an adversary's view. Two consequences of the gate are non-obvious and testable:

1. A shared bridge is a linkability hazard (RQ1). When federated houses route through one shared bridge node, that node observes both the entry and exit segments of circuits crossing it. Modern flow-correlation attacks link such segments at high accuracy from timing/volume alone [NasrBH18; OhYMH22; RahmanSMGW20]. We ask whether our bridge exhibits a measurable entry↔exit correlation leak, and whether cover padding closes it.

2. Consent-gating can funnel, not just spread (RQ2). Federation intuitively enlarges the candidate-sender set and thus anonymity [Serjantov2002; Diaz2002]. But a consent gate means only willing relays carry traffic; if willingness concentrates on a few bridges, circuits funnel through them and the effective anonymity set may shrink. We therefore treat the sign of the federation effect as unknown a priori and report a shrink as prominently as a growth.

Contributions. (i) The design and instrument-grade implementation of a consent-gated, federated, nested-SSH relay data plane with signed in-band accept/reject and per-hop X25519 credentials (§3, §4). (ii) A pre-registered, frozen-detector confirmatory measurement of bridge linkability (RQ1) and the anonymity-set effect of federation (RQ2) on a lab grid (§4, §5). (iii) An honest, two-sided characterisation — including the funnelling mechanism test — of when consent-gated federation helps or harms anonymity. [Quantitative findings — HELD BLIND.]

Scope. Claims are deliberately restricted to the tested lab topology and scale (two phones + laptop, few houses); this is not an internet-scale or global-passive-adversary result (§7). The paired churn-resilience question (RQ3) and a QUIC/ssh3 transport arm [Michel2023] are pre-registered but held for a companion paper; this lead paper covers G4 + RQ1 + RQ2 only.

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2. Related work

Onion routing and SSH-based relays. Mixes and onion routing originate with Chaum [Chaum1981] and Reed–Syverson–Goldschlag [Reed1997], with Tor [Dingledine2004] as the dominant deployment. SOR [Egners2012] is the direct prior art: it layers onion routing over stock SSH tunnels, which is exactly our transport substrate. Nesting SSH inside SSH raises the well-known TCP-over-TCP throughput/latency pathology [Honda2005], motivating our latency-aware measurement and a (exploratory) QUIC-based ssh3 transport [Michel2023]; UDP-based latency work on onion services [AlAzad2023] is complementary. None of these model per-circuit relay consent, which is the axis we add and measure.

Flow correlation / linkability (RQ1). That an adversary seeing two segments of a flow can link them is established: low-cost traffic analysis [MurdochD05], realistic-adversary correlation on Tor [JohnsonWJSS13], and deep-learning correlators DeepCorr [NasrBH18] and DeepCoFFEA [OhYMH22] achieve high linking accuracy; packet-timing (Tik-Tok [RahmanSMGW20]) and deep fingerprinting [SirinamIJW18] show timing/volume suffice. We do not advance correlator state-of-the-art; we adopt a frozen, fixture-calibrated correlator (calibration gate §5) and use its AUC purely as an instrument reading of whether our bridge leaks — the contribution is the consent-gate/bridge measurement, not the attack.

Anonymity metrics and Sybil/directory concerns (RQ2). We quantify anonymity with the information-theoretic set metrics of Serjantov–Danezis [Serjantov2002] (entropy of the adversary posterior; effective set size S = 2^H) and Díaz et al. [Diaz2002] (normalized degree d = H/log₂N). Federation across mutually-distrusting houses evokes decentralised-directory and Sybil questions [Douceur2002; Winter2016] and statistical-disclosure exposure over repeated circuits [Danezis2003]. Our matched-N design isolates the topology effect (federated vs. single-house at equal total node count) rather than a node-count artifact.

Social-trust / consent-adjacent designs (G4 neighbours). The closest neighbours treat relaying willingness or social linkage as structural: Freenet's friend-to-friend mode [Clarke2000], membership-concealing overlays [Vasserman2009], Drac's social low-volume comms [Danezis2010], and social-graph routers Pisces [Mittal2012] / X-Vine [Mittal2012b] / STor [Zhou2011]. These encode trust in the graph; none makes consent an in-band, per-circuit, signed accept/reject protocol step whose linkability and anonymity-set consequences are then measured — the specific gap G4 fills.

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3. System design (the instrument)

The instrument is a nested-SSH relay data plane built into an existing zero-knowledge chat relay (hack-house), entirely within an isolated worktree. It has seven components (roadmap R1–R7); the subset load-bearing for this lead paper (RQ1 + RQ2, static selector, no model) is fully pinned by the freeze. Key mechanisms:

• Consent handshake (R5). Each hop receives a signed in-band consent request and must accept or reject before it will carry the circuit. Requests are Ed25519-signed by the originating persona and verified before acceptance; an unsigned or forged request is rejected. Per-hop credentials are X25519-sealed to the host's public key, so a hop credential decrypts only with that host's private key (no shared-symmetric secret).
• Nested-SSH circuits (R4). A circuit is a chain of SSH tunnels across grid hops; the entry and exit segments are the observable units for RQ1. Every hop's traffic is captured to an immutable per-hop pcap, written once and checksummed.
• Federation / bridge (R6). Relays are grouped into houses. Houses federate via a shared bridge node or via a directory; a circuit's federation path is chosen under split-knowledge topology constraints. The bridge is the shared observation point RQ1 probes and the concentration point RQ2's funnelling test probes.
• Determinism & provenance (R1–R3). All stochastic behaviour derives from a single --sor-seed; the seed, git SHA, and node-role→device mapping are echoed into an immutable manifest.json, and every relay event is appended to a SHA-256-sealed events.jsonl.
• Containment (binding). Every forwarder runs in an isolated engine only (assert engine != local or the run refuses). All traffic is self-generated to our own fixtures, lab-only. No external target, no live-network relay.

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4. Methods (pre-registered; frozen)

This study is a confirmatory factorial controlled comparison; the design, variables, seeds, detectors, and analysis were frozen and hashed on 2026-07-19 before any confirmatory cell ran.

4.1 Design matrix

Cells are organised per RQ with the other factors held at their declared control:

• RQ1 (linkability): bridge ∈ {off, on, on+padding} — 3 levels; topology held at single-house, selector static. (bridge-off+padding is declared N/A — padding is defined only for bridge-on.)
• RQ2 (anonymity set): topology ∈ {1-house-N, bridge-federated, directory-federated} at matched total node count N — 3 levels; bridge held off, selector static.

Full crossing is not run. Run order is randomised within each cell and the control arm is interleaved before and after treatments so grid calibration drift is caught. All stochastic elements are seed-controlled.

4.2 Dependent variables

• RQ1 — correlation AUC. Area under the ROC of the frozen flow-correlation detector scoring (entry-segment, exit-segment) pairs as same/different circuit, measured from the real per-hop pcaps. Unit of analysis: the (entry, exit) pair; 95% CI by bootstrap over circuit pairs.
• RQ2 — anonymity-set entropy H. Shannon entropy of the adversary's posterior over candidate senders per circuit; effective set size S = 2^H [Serjantov2002], normalized d = H/log₂N [Diaz2002]; Miller–Madow finite-sample bias correction; 95% CI by bootstrap over circuits. Unit of analysis: the circuit. ΔH = H(federated) − H(single-house, matched N).

  Construction caveat (hard hold). The prereg pins this DV as a per-circuit posterior but does not give the posterior construction rule. A construction — uniform mass over the observation-consistent anonymity set, grounded only in [Serjantov2002; Diaz2002] — is PROPOSED in docs/stage-05-rq2-posterior-clarification.md and awaits operator ratification. Until ratified, no RQ2 number is computed. The construction is recomputable offline from the sealed per-circuit seeds (deterministic circuit assembly), so the running battery is not wasted regardless of the ratified rule.

4.3 Sampling & power

R = 30 independent seeded runs per cell; each run builds C = 50 circuits (≥ 1500 scored pairs per cell for RQ1). The target is precision, not a formal power analysis: ≥ 1500 pairs yields an expected bootstrap 95% CI half-width on AUC ≤ 0.03, enough to resolve the RQ1 floor away from 0.5. One base seed S0 = 20260719; per-cell seed = SHA256(S0 ‖ cell_id ‖ run_index) truncated to u64, echoed into every manifest. Stopping rule: all cells × R runs run to completion — no optional stopping, no interim looks; an uninformative cell is reported inconclusive, never extended to chase significance.

4.4 Frozen detectors and the instrument-validation gate

Detectors (correlator, entropy estimator, classifier) are written and calibrated only on the instrument-validation fixtures — known-linked/known-unlinked control pairs and equiprobable-sender synthetic sets — before any confirmatory cell is run; no per-cell tuning is permitted. The battery ran only after all six boolean gate items passed green: (1) 3-hop end-to-end delivery with per-hop pcap + checksum; (2) seeded reproducibility (same seed → identical circuit-build sequence); (3) correlator calibration (known-linked AUC ≈ 1, known-unlinked ≈ 0.5); (4) entropy calibration (H = log₂N for N equiprobable senders); (5) isolation (assert engine != local or refuse); (6) provenance integrity (replayed fixture → schema-valid events.jsonl whose SHA-256 matches the manifest; append-only).

4.5 Analysis plan

Effect size + 95% CI for every comparison; p-values never reported alone. All inference is bootstrap/permutation-based (10,000 resamples, BCa intervals; 3-seed spot-check to MC error).

• RQ1-P1 (leak). Bridge-on correlation AUC, bootstrap 95% CI. Confirmation gate = CI excludes 0.5 (leak present); null if CI includes 0.5. Materiality is a separate label: CI lower bound ≥ 0.60 ⇒ "material leak"; between 0.5 and 0.60 ⇒ "weak-but-real leak."
• RQ1-P2 (padding efficacy). ΔAUC = AUC(bridge-on, no-pad) − AUC(bridge-on, +pad); paired bootstrap 95% CI. Padding effective iff ΔAUC CI > 0.
• RQ2-P1 (federation effect, two-sided). ΔH bootstrap 95% CI; the sign is not presumed. grow if CI > 0; honest shrink (reported with equal prominence) if CI < 0; inconclusive if it spans 0. (Computation gated on RQ2 ratification.)
• RQ2-P3 (funnelling mechanism). Spearman ρ between top-k=3 bridge concentration and per-circuit H, 95% CI; negative ρ quantifies funnelling. (Computation gated on RQ2 ratification.)
• Multiple comparisons. Holm–Bonferroni over the frozen family of 7 confirmatory tests {RQ1-P1, RQ1-P2, RQ2-P1, RQ2-P3, RQ3-P1-perf, RQ3-P1-latency, RQ3-P2}; the 4 lead-paper tests are reported at Holm-adjusted multipliers 7, 6, 5, 4 (conservative embedding — see docs/stage-05-holm-clarification.md, ratified). EXPLORATORY results (QUIC transport; any post-hoc contrast) are labelled and excluded from the confirmatory column.
• Data exclusion (pre-data). A run is quarantined (logged, never silently dropped) only on a data-integrity failure (SHA mismatch, pcap checksum failure, in-place edit, or non-reproducing seed). No performance-based exclusions.

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5. Results (HELD BLIND — placeholders)

Populated once, after the full battery completes and raw outputs are sealed. RQ2 subsections additionally gated on ratification of the posterior construction. No confirmatory number appears until then.

5.1 Instrument-validation gate report

[HELD — will report the six boolean gate outcomes and calibration AUC/entropy values.]

5.2 RQ1 — bridge linkability

[HELD — RQ1-P1 bridge-on AUC + BCa CI and materiality label; RQ1-P2 paired ΔAUC + CI.]

5.3 RQ2 — anonymity-set effect of federation

[HELD + RATIFICATION-GATED — RQ2-P1 ΔH + CI (grow/shrink/inconclusive); RQ2-P3 Spearman ρ + CI.]

5.4 Holm-corrected confirmatory summary

[HELD — the 4 lead-paper tests at Holm-adjusted levels, effect sizes + CIs.]

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6. Discussion (HELD BLIND — placeholder)

[HELD — interpretation of the confirmed/null/inconclusive outcomes; the honest-null story if ΔH shrinks; what the funnelling ρ implies for consent-gated federation; padding efficacy.]

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7. Limitations & threats to validity

• Scale / adversary model (External). The grid is two phones + a laptop and few houses; this is not internet-scale and not a global passive adversary. Claims are scoped to the tested topology/scale; entropy CIs are wide at small node counts (accepted, node counts reported).
• Construct. Self-generated fixture traffic is not real user traffic (inherent to lab measurement; fixtures versioned/checksummed). A single correlator's AUC stands in for "linkability" and plug-in H for "anonymity" — mitigated by fixture calibration (§4.4) and by reporting S = 2^H and normalized d; a second entropy estimator (NSB) is reported EXPLORATORY as a sensitivity check.
• Internal. Thermal/background load and device heterogeneity are mitigated by randomised order, interleaved controls, per-session idle baselines, and a pinned node-role→device mapping. Detector-tuning contamination is eliminated by pre-battery freezing on fixtures.
• RQ2 construction dependency. The RQ2 result depends on the ratified posterior construction (§4.2 caveat); the construction is pre-specified blind, two-sided, and grounded only in cited metrics — but it is a specification the frozen prereg did not pin, and is disclosed as such.
• Dual-use (ethics). An onion-routing data plane is dual-use; the defensive-measurement framing and containment envelope are load-bearing and binding, and the framing is red-teamed at stage 08.

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8. Deviations from pre-registration

Tracked only in stage-05 sor-consent-deviations.md (none edit the frozen prereg). Two clarifications recorded to date: the Holm family-size restatement (docs/stage-05-holm-clarification.md, ratified) and the RQ2 posterior construction (docs/stage-05-rq2-posterior-clarification.md, PROPOSED — pending operator ratification).

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References

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(Full bibliography: ~/coding/sci-method/stages/01-literature/output/sor-consent-bibliography.md. Integrity flags carried forward: [Stutzbach2006] secondary-sourced; [Constantinides2026] recent preprint — neither is load-bearing in this lead paper.)