Inside CHIMERA: Synthesizing Frankenstein Sessions

## 1. Why Naive Splices Get Caught

If an attacker blindly cuts two mouse trajectories mid-flight, the sudden velocity discontinuity or jerk spike will be immediately flagged by derivative-based classifiers like RF-lite.

2. The 5-Stage CHIMERA Pipeline

1. Pause-Boundary Segmentation: CHIMERA scans donor sessions to find points where mouse velocity $v \approx 0$ (dwell points). Splicing at stationary pauses is geometrically invisible to acceleration/jerk detectors.
2. Multi-Source Recombination: Fragments are selected from 3 distinct human donors to ensure the composite matches no single historical session in a DTW database.
3. Similarity Transform Retargeting: A transformation matrix (translation, rotation, scale) adjusts trajectories to match target input locations while scaling timestamps to preserve natural velocity.
4. Uniform Retiming & Micro-Jitter: Applies a random scaling factor ($0.90\times - 1.15\times$) to defeat exact-match timing filters.
5. Cross-Participant Keystroke Overlay: An independent typing stream is overlaid on the composite mouse timeline, creating the fatal cross-modal coherence break that CMCC catches.