Stealth Is a Relation, Not a Property: How Event Representations Create Blind Spots for Timing Attacks in Event-Based Perception

An event camera produces an asynchronous stream, but what is visible in that stream depends on how a downstream consumer, such as a model or detector, processes time. The same timestamp change may leave a coarse temporal representation unchanged while changing the response of a model that preserves finer timing. This creates blind spots that timing attacks can exploit. We characterize this dependence as observer-relative stealth. For recorded event streams, retiming an event within its protected accumulation window leaves the accumulated integer tensor exactly unchanged. Any consumer that receives only this tensor, therefore, sees the same input before and after the attack. We use this exact blind space to construct Null, a gradient-guided timestamp-retiming attack, and define ${\mathrm{SC}\text{-}\mathrm{ASR}}_A(\tau )$ to measure attack success while bounding the change visible to observer $A$. Across five event-vision datasets, the exact blind space contains retimings that remain exactly hidden from the protected observer while causing victim failure. On DVS Gesture at a 10% event budget, Null reaches $81.56\pm 5.81\%$ ASR on ConvSNN and $98.67\pm 0.45\%$ on a GRU while preserving the protected tensor exactly. On DailyDVS-200, a protocol-scale Multi-View Fusion Network variant reaches $99.28\pm 0.11\%$ exact-null ASR, compared with $9.70\pm 1.06\%$ for its matched control. In a five-attack comparison, Null is the only method with nonzero attack success at exact observer equality, reaching $81.4\%$ on DVS Gesture and $87.35\%$ on DailyDVS-200. We also search the same exact blind space with an independently implemented constrained projected-gradient optimizer, C-PGD. At matched victim-gradient evaluations, C-PGD reaches $84.50\pm 2.89\%$ ASR on DVS Gesture and $89.55\pm 4.39\%$ on DailyDVS-200, again with exact protected equality. Both optimization procedures find retimings with high attack success within the exact same blind space. We then change the temporal observer and test the same attacks. Perturbations that are exactly hidden from the protected observer become visible under shifted, finer, overlapping, and randomized temporal views. Adding observer constraints reduces the real-valued blind-space fraction from $87.5\%$ to $75.0\%$ to $62.5\%$, while DVS ConvSNN ASR falls from $74.9\%$ to $61.9\%$ to $37.2\%$. These results show that stealth is not a property of the perturbation alone. It depends on the temporal information available to the observer.