Mission-Aware Attestation Envelopes for Time-Critical Autonomous Action: A Hardware-in-the-Loop V2I Study

Dimitrios Nikou; Nikolaos Kekatos; Sophia Petridou; Stylianos Basagiannis

cs.CROct 6, 2026

Mission-Aware Attestation Envelopes for Time-Critical Autonomous Action: A Hardware-in-the-Loop V2I Study

Authors: Dimitrios Nikou, Nikolaos Kekatos, Sophia Petridou, Stylianos Basagiannis

Organizations: International Hellenic University, Greece · Clone Systems, Cyprus · University of Macedonia, Greece

Abstract

An autonomous system that asks for a privileged physical action is usually gated on integrity evidence: a platform proves what it is running, and the request is granted or refused on that basis. Such a gate is normally treated as a predicate, yet the evidence behind it has an age, the decision that consumes it has a latency, and the physical system that waits for it has a deadline. We formulate mission-aware attestation as a runtime assurance contract that holds only when integrity is valid, the evidence is fresh enough, and the decision completes inside a budget derived from the current physical state. The contract yields four operational outcomes where a binary gate yields two, separating a refusal caused by tampering from one caused by stale evidence and from one caused by a late decision. We evaluate it on a hardware-in-the-loop vehicle-to-infrastructure platform: a driving simulator supplies the physical state and the authorisation deadline, while a microcontroller on-board unit and a TPM-backed roadside unit running Linux integrity measurement supply the assurance evidence. A security-blind model admits the whole operating space and a hardware-informed one three quarters of it, and every point it refuses fails the freshness margin rather than the response margin. Moving the attestation interval across the range the verifier permits costs about as much as a fivefold scaling of the latency distribution, and the interval is directly configurable, which makes it the immediately actionable deployment parameter. If the freshness bound does not exceed the authorisation budget, every late decision is also stale and lateness becomes unobservable, so the attestation interval and the freshness bound cannot be chosen from security requirements alone.

Figures & tables

Panel of Figure 1 — Figure 1: The authorisation loop, with steps numbered as in the text. Dashed verticals are component lifelines and time runs downwards.

Symbol	Meaning
$R$ , $V$ , $P$ , $W$	requester, decision point, evidence source, plant
$t_{r}$ , $t_{d}$	time the request is issued, time the decision is taken
$t_{a}$	time the integrity evidence used by that decision was generated
$x_{r}=(d_{r},v_{r})$	plant state at the request: distance to actuation, speed
$T$	attestation interval
$T_{\max}$	verifier liveness threshold: longest tolerated gap between quotes

Table 1: System-model notation. The contract of Sect. 3 adds

D

F_{\max}

M_{R}

and

M_{F}

, properties of the assurance policy rather than facts about the system.

Panel of Figure 2 — Figure 2: The two ways an authorisation can fail while integrity holds. Above the axis, the evidence had already aged before the request, and the age it reaches by the decision overruns the freshness bound $F_{\max}$ . Below the axis, the evidence would have been acceptable and the decision latency overruns the authorisation budget $D(x_{r})$ that the physical state allows. The two are measured from different origins, $t_{a}$ and $t_{r}$ , which is why neither implies the other in general; Sect. 3.3 gives the condition under which one does imply the other. Shaded spans are the overruns.

Outcome	Violated	Example condition
PERMIT	nothing	normal operation
DENY-INTEGRITY	$\mathit{integrity}$	rogue on-board unit; modified decision-point host
DENY-STALE	$M_{F}$	periodic re-attestation, request late in the interval
DENY-LATE	$M_{R}$	contention exhausting the budget

Table 2: Outcomes of the assurance contract, and what produces each on the platform.

Panel of Figure 3 — Figure 3: Hardware-in-the-loop topology. The dotted region is real: a physical microcontroller, a TPM-backed host running Linux integrity measurement, and the contended transport between them. Only the vehicle and the intersection are simulated.

Panel of Figure 4 — Figure 4: The physical state is simulated and the assurance evidence is measured. CARLA supplies distance and speed at the moment of the request; the ESP32 supplies the admission payload that the roadside unit checks.

Configuration	$n$	mean	median	p95	max obs.
End-to-end, no contention	50	422.8	419.8	559.2	624.2
Attestation component	50	33.3	20.0	93.9	147.3

Table 3: The measured latency distribution, without channel contention, from which

Q(q)

is taken. Extremes are maxima observed rather than bounds. The loaded arm survives as summary statistics only, used in Sect. 5.1 for the existence test alone.

quantity	loaded min	exceeds	$p$	verdict
End-to-end	438.67 ms	31 / 50	$2.5\times 10^{-3}$	supported
Attestation component	14.40 ms	0 1 / 50	$0.88$	no evidence

Table 4: Exact rank test on the loaded arm: its minimum against the fifty unloaded samples. Exceedance is strict, so the one observation equal to the attestation minimum is not counted.

configuration	slope	50 km/h	80 km/h	110 km/h
$\phi=0$ , $T=2$ s	0.56 s	7.8 m	12.4 m	17.1 m
$\phi=0.5$ , $T=2$ s	1.56 s	21.7 m	34.6 m	47.6 m
$\phi=1$ , $T=2$ s	2.56 s	35.5 m	56.9 m	78.2 m
$\phi=1$ , $T=10$ s	10.56 s	146.7 m	234.6 m	322.6 m

Table 5: Minimum trigger distance from Eq. ( 6 ),

Q(0.95)=559.2

ms.

interval	feasible	gap	infeas.	note
0.5 s	54 / 60	10.0%	6	below the configured period
1.0 s	52 / 60	13.3%	8	below the configured period
2.0 s	46 / 60	23.3%	14	configured period
5.0 s	35 / 60	41.7%	25	between the two
10.0 s	24 / 60	60.0%	36	maximum the verifier tolerates

Table 6: Feasible operating points against the evidence-age bound, under an empirical

95\%

satisfaction criterion over the sixty-point space, with

F_{\max}=D(x_{r})

, justified in Sect. 3 . The verifier reports a configured period of

2

s and a tolerated maximum of

10

s; the two shorter intervals are included to show the trend below the configured value. Every infeasible point fails on freshness and none on timeliness, which is the masking result of Sect. 3.3 rather than an empirical finding: at

F_{\max}=D

the freshness test subsumes the response test, so no point can fail the latter alone.

		infeasible
factor	feasible	age-only	age $+$ latency
1.00	46 / 60	9	5
1.27	44 / 60	9	7
1.50	43 / 60	9	8
2.00	41 / 60	9	10
3.00	35 / 60	9	16

Table 7: Sensitivity of the envelope to a modelled contention slowdown, at the nominal

2

s interval. The scaling is applied to the measured unloaded distribution; the

1.27

row is the ratio of the pilot’s loaded and unloaded means, shown for reference only. An infeasible point is age-only when it remains infeasible with latency set to zero, and age

+

latency otherwise. The first column is constant by construction, since that test does not involve the scaling. No point is infeasible on latency alone; see Table 6 .

Scenario	Binary gate	Contract	Source
Genuine requester, clean host	permit	PERMIT	executed
Rogue on-board unit	deny	DENY-INTEGRITY	executed
Modified decision-point host	deny	DENY-INTEGRITY	executed
Valid but aged evidence	permit	DENY-STALE	Table 6

Table 8: Binary gate against the assurance contract. The integrity rows are executed on hardware. The stale row is not a separate experiment: it is the region Table 6 shows the contract refuses and the gate admits. DENY-LATE does not appear, for the reason given in Sect. 3.3 .

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