leetcrypt
1c6063248f
RQ2-P3 mechanism study (NEW prereg, approved-path/params-locked, not yet frozen):
pool-based willing-bridge instrument, concentration swept as a manipulated IV
(B∈{2,4,8}×α∈{0,1,2}), two-sided/direction-agnostic, run-level cluster bootstrap.
RQ3 companion run-brief (execution-freeze for the already-frozen RQ3): agent=qwen2.5:3b
local Ollama, churn kill_prob=30/steps=20, baselines + Holm-7 completion pinned.
note-unique-bridge-artifact.md: on-record analysis that the lead RQ2-P1 shrink is plausibly
a fresh-bridge-per-circuit artifact (unique exit-signature -> singleton set -> H~0), and that
realistic bridge reuse (a mix) may raise anonymity -> the mechanism study may qualify the lead
RQ2 headline. No edit to the frozen prereg or committed lead paper.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
55 lines
3.3 KiB
Markdown
55 lines
3.3 KiB
Markdown
# Note — the RQ2-P1 "shrink" is plausibly a unique-bridge instrument artifact
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**Status:** on-record analysis note, 2026-07-21. Does **not** edit the frozen prereg or the
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committed lead paper; it documents a mechanism concern for the record and motivates the
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`rq2p3-mechanism-prereg.md` follow-up. Author: overseer, post-lead-paper review.
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## The finding
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The lead paper (RQ2-P1) reports federation **shrinks** the per-circuit anonymity set
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(ΔH = −0.96 bits pooled; −3.63 bits bridge-federated-only, exploratory). Tracing the ratified
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posterior mechanically shows this shrink is **largely forced by the instrument**, not by a
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substantive funnelling phenomenon:
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1. The adversary's observation is `exit_signature = (exit_house, bridge_label)`
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(`confirm_load_rq2.py:exit_signature`).
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2. The anonymity set for circuit *i* is the distinct **entry** nodes among circuits sharing
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*i*'s signature (`observation_consistent_sizes`): `m_i = |{entry(j) : sig(j) == sig(i)}|`.
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3. The bridge-federated instrument assigns a **fresh bridge per circuit seed**
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(`assembler.py:_bridge_label(seed)`), so **every circuit's `bridge_label` is unique** ⇒
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every `exit_signature` is unique ⇒ each group has size 1 ⇒ **`m_i = 1` ⇒ `H_i ≈ 0`.**
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So bridge-federated collapses to near-zero entropy **because each circuit was handed its own
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bridge**, making its signature a unique identifier. That is the *same* degeneracy that made
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RQ2-P3 untestable (zero-variance concentration) — here it manifests as an artificially low H
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that drives ΔH negative.
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## Why this likely inverts under realistic bridge reuse
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Introduce a finite shared bridge **pool**: many circuits share a bridge ⇒ shared signature ⇒
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`m_i` = distinct entries across all of them ⇒ **larger set ⇒ higher H**. Under this posterior
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a shared bridge behaves as a **mix**: more concentration plausibly *raises* anonymity — the
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opposite of the naive "funnelling shrinks the set" story. The mechanism study
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(`rq2p3-mechanism-prereg.md`) tests this **two-sided**; the mechanical prediction is mix
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(ρ > 0), the naive prediction is funnel (ρ < 0).
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## Consistency check against observed numbers
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- Directory-federated cell (no bridge hop → `bridge_label = None`, shared signature):
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observed `rq2_anonymity_entropy_bits = 5.6439 = log₂(50)` — **maximal** entropy, all 50
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senders in the set. Confirms shared signatures give large sets.
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- Bridge-federated (unique bridge per circuit): H ≈ 0, consistent with the exploratory
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ΔH = −3.63. The pooled −0.96 is the average of a high-H directory arm and a ≈0-H bridge arm.
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## Integrity status
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- The lead paper is **not wrong or dishonest**: §7 already flags RQ2 as conditional on the
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posterior construction and RQ2-P3 as an unresolved mechanism. This note **sharpens** that
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caveat from "conditional" to "the specific shrink magnitude is mechanically forced by the
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fresh-bridge instrument."
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- **No silent edit** to the committed paper or frozen prereg. If the mechanism study confirms
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mix (ρ > 0), the honest outcome is a companion result that **qualifies/corrects** the lead
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RQ2-P1 headline — reported openly, per the null-results-are-results rail.
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- This strengthens the body of work: it is exactly the kind of artifact a pre-registered,
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frozen-detector method is supposed to expose rather than bury.
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