Marcin Pawlowski a93311013b
reports/blend/pd: section 3.10, cover traffic
Written from configs/cover-traffic.yaml: the rate swept over three decades against
three release delays, each timeline paired with the epoch emission budget.

The finding that shapes the section is that mixing never happens. At one message
per second a relay holds 0.0014 messages and never more than two; even 256x the
rate reaches only 0.39, matching Little law exactly. So the anonymity set is
entirely blending -- the broadcasts a relay saw between releases -- which follows
rate*(2M+1)/3, twice the mean hold. Measured within ~1% over most of the range.

That makes delay the cheap lever: both knobs enter linearly, but bandwidth is paid
on every link while delay is paid once per hop. An anonymity set of 100 costs 42.9
msg/s at a 3s delay and 4.9 msg/s at 30s.

The quota ceiling is the hard edge. A node proposals must fit its emission budget,
capping stake at ln(1-q)/ln(1-f) of INFERRED stake -- about 0.1% at the baseline
rate once Poisson fluctuation is allowed for. A 9.5% holder overruns by ~65x and
is distinguishable by emission count alone, before any path is captured.

Two existing sections needed correcting as a result. 3.6-3.7: with cover traffic
running, catching an emission is not catching a block, and the large stakers those
sections analyse sit one to two orders of magnitude above the quota ceiling, so
their binding exposure is the quota rather than the cascade. 5: the timing-
correlation adversary was deferred for want of cover traffic and is now unblocked.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-06 17:59:59 +02:00

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Evidence of record

The sweep outputs behind every number in the report. The simulator does not commit its own runs/ directory — these are the copies of record, kept so that any figure or table can be re-derived, or challenged, without re-running hours of compute.

Each run directory holds the three tables the simulator writes: propagation.parquet, adversary.parquet and deanon.parquet.

directory config sampling backs
default/ configs/default.yaml 1 000 rounds × 8 seeds = 8 000/cell §3.1§3.5 — delay, observation, eclipse, deanonymization, delivery, coverage
redundancy/ configs/redundancy.yaml 1 200 × 8 = 9 600/cell §3.8 — messaging redundancy R = 1…4
percolation/ configs/percolation.yaml 800 × 8 = 6 400/cell §3.5 — the churn threshold u_c = 1 1/(degree 1)
correlated-churn/ configs/correlated-churn.yaml 800 × 8 = 6 400/cell §3.9 — correlated AS/region outages vs uniform churn
fullscale/ configs/fullscale.yaml 64 × 3 = 192/cell §5 — the 10⁶ scaling check (deliberately lighter; not a source of headline numbers)
cover-traffic/ configs/cover-traffic.yaml 900 s timeline × 4 seeds §3.10 — blending, mixing, and the emission-quota stake ceiling. Carries a fourth table, traffic.parquet

The linkability results (§3.6§3.7) and both deanonymization rates are closed forms over these tables rather than separate measurements, so they have no run of their own — pd.linkability derives them and make verify checks them against Monte-Carlo.

Regenerating the report's numbers

python report_numbers.py

prints every quoted value with its across-topology standard error, straight from the parquets here. That is the fastest way to check a table in the report against its evidence. It takes optional paths (report_numbers.py <default> <redundancy> <percolation>) if you want to point it at fresh runs instead.

Regenerating the data itself

From tools/simulators/blend/pd: make sweep, make redundancy, make percolation, make correlated-churn, make sweep-fullscale. Results land in that simulator's runs/<timestamp>_<label>/. Note that the seed streams depend on the configuration, so re-running reproduces the statistics, not bit-identical numbers, unless the config is unchanged — in which case it does reproduce exactly.

Two runs from the same session are deliberately not kept: the smoke runs (throwaway, far too noisy to interpret) and an earlier 144-rounds/cell redundancy grid that was superseded because its sampling error produced a non-monotonic delivery curve — the reason redundancy/ samples 9 600.