Marcin Pawlowski 61d72bb5f5
pd: wire cover traffic through the sweep as a fourth table
engine gains a cover_rates axis: each rate plays a timeline through the same
graph and pairs it with the epoch emission budget, which needs no graph and so is
computed alongside rather than inside the window. Seeds are separate streams
(traffic_seedseq for the timeline and clocks, stake_seedseq for the stake draw
and budget), so the stake distribution is independent of the topology and of the
message schedule.

sweep writes traffic.parquet only when a cover-traffic study actually ran, so
every existing config keeps producing exactly three tables. quota_summary reports
the measured ceiling beside the predicted one in the same row, so a run can be
checked against the closed form instead of asked to be believed.

Two figures: blending against cover rate and release delay with the
rate*(2M+1)/3 law overlaid, and the quota ceiling with the measured transition
band against the prediction.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-06 17:59:58 +02:00

101 lines
4.9 KiB
Python

"""Deanonymization metrics: exact closed forms + a Monte-Carlo tie to the actual draw.
A *deanonymization* event is a round whose whole blend path is adversarial; *full* deanonymization
additionally requires the honest sender to be directly peered with an adversary. Relays are drawn
uniformly blind to who is adversarial, so both rates are exact (no sampling in production)."""
import numpy as np
from pd.adversary import adversary_metrics, deanon_metrics, place_adversary
from pd.config import SimConfig
from pd.engine import run_graph_cell
from pd.graph import build_graph
def test_deanon_rate_hand_computed():
# n=4, 2 adversaries, honest sender leaves 3 nodes (2 adversarial) in the relay pool;
# k=2 distinct relays both adversarial: C(2,2)/C(3,2) = 1/3.
dz = deanon_metrics(n=4, n_adv=2, observed_frac=0.5, blend_hops=2)
assert abs(dz["deanon_rate"] - 1.0 / 3.0) < 1e-12
assert abs(dz["full_deanon_rate"] - (1.0 / 3.0) * 0.5) < 1e-12
def test_deanon_rate_zero_when_too_few_adversaries():
assert deanon_metrics(n=100, n_adv=1, observed_frac=0.9, blend_hops=2)["deanon_rate"] == 0.0
assert deanon_metrics(n=100, n_adv=0, observed_frac=0.0, blend_hops=1)["deanon_rate"] == 0.0
# too few adversaries -> no full deanonymization either
too_few = deanon_metrics(n=100, n_adv=1, observed_frac=0.9, blend_hops=2)
assert too_few["full_deanon_rate"] == 0.0
def test_full_deanon_is_deanon_times_observed():
dz = deanon_metrics(n=5000, n_adv=1000, observed_frac=0.73, blend_hops=3)
assert abs(dz["full_deanon_rate"] - dz["deanon_rate"] * 0.73) < 1e-12
assert dz["full_deanon_rate"] <= dz["deanon_rate"] + 1e-12
def test_deanon_rate_is_placement_independent_but_full_is_not():
"""The whole-path-adversarial rate depends only on the adversary COUNT; the full rate also
tracks how many honest nodes are peered with an adversary, which the worst case maximizes."""
g = build_graph(SimConfig(n_nodes=2000, degree=6, graph_seed=0))
rng = np.random.default_rng(0)
rand = adversary_metrics(g, place_adversary(g, 0.2, "random", rng, 10**9))
wc = adversary_metrics(g, place_adversary(g, 0.2, "worstcase_coverage", rng, 10**9))
assert rand["n_adv"] == wc["n_adv"] # same budget
dz_rand = deanon_metrics(g.n, rand["n_adv"], rand["observed_frac"], 3)
dz_wc = deanon_metrics(g.n, wc["n_adv"], wc["observed_frac"], 3)
assert abs(dz_rand["deanon_rate"] - dz_wc["deanon_rate"]) < 1e-12 # placement-independent
assert dz_wc["full_deanon_rate"] >= dz_rand["full_deanon_rate"] - 1e-12 # worst case >= random
def test_deanon_asymptotic_fadv_power():
# C(A,k)/C(n-1,k) -> f_adv^k for large n.
f, k, n = 0.3, 3, 20000
dz = deanon_metrics(n=n, n_adv=int(round(f * n)), observed_frac=0.5, blend_hops=k)
assert abs(dz["deanon_rate"] - f ** k) < 0.002
def test_deanon_matches_direct_sampling():
"""Closed form == empirical rate of the exact honest-sender/blind-relay draw the sim uses."""
f, k = 0.33, 2
cfg = SimConfig(n_nodes=1500, degree=8, graph_seed=3, f_adv=f, blend_hops=k)
g = build_graph(cfg)
mask = place_adversary(g, f, "random", np.random.default_rng(1), cfg.worstcase_max_n)
adv = adversary_metrics(g, mask)
dz = deanon_metrics(g.n, adv["n_adv"], adv["observed_frac"], k)
counts = np.add.reduceat(mask[g.indices].astype(np.int32), g.indptr[:-1])
observed_node = counts >= 1
honest = np.where(~mask)[0]
n = g.n
rng = np.random.default_rng(42)
trials, d_hit, fd_hit = 40_000, 0, 0
for _ in range(trials):
s = int(rng.choice(honest))
r = rng.choice(n - 1, size=k, replace=False)
r[r >= s] += 1
if mask[r].all():
d_hit += 1
fd_hit += int(observed_node[s])
assert abs(dz["deanon_rate"] - d_hit / trials) < max(0.006, 0.1 * dz["deanon_rate"])
assert abs(dz["full_deanon_rate"] - fd_hit / trials) < max(0.006, 0.12 * dz["full_deanon_rate"])
def test_engine_emits_deanon_rows():
base = SimConfig(n_nodes=1000, degree=8, graph_seed=0, n_placements=2)
prop_grid = [(2, 0), (3, 0)] # distinct blend_hops = {2, 3}
adv_grid = [(0.2, "random"), (0.0, "random")]
prop_rows, adv_rows, deanon_rows, _ = run_graph_cell(base, prop_grid, [0.0], [1], adv_grid)
# one deanon row per (placement, distinct blend_hops, redundancy)
assert len(deanon_rows) == len(adv_rows) * 2
cols = {"n_nodes", "degree", "blend_hops", "redundancy", "f_adv", "adversary_mode",
"graph_seed", "placement_rep", "n_adv", "n_honest", "observed_frac",
"deanon_rate", "full_deanon_rate"}
assert cols <= set(deanon_rows[0])
assert {row["blend_hops"] for row in deanon_rows} == {2, 3}
for row in deanon_rows:
assert 0.0 <= row["full_deanon_rate"] <= row["deanon_rate"] + 1e-12
if row["f_adv"] == 0.0:
assert row["deanon_rate"] == 0.0 # no adversary -> no deanonymization