Zero-Storage Spatiotemporal Key Generation with Adiabatic Charge-Recovery Logic for Resilient Flapping-Wing Microrobotics

Technical Summary: Zero-Storage Spatiotemporal Key Generation with Adiabatic Charge-Recovery Logic for Resilient Flapping-Wing Microrobotics

1. Problem Statement

Flapping-wing micro air vehicles (FW-MAVs) operate under extreme Size, Weight, and Power (SWaP) constraints, typically carrying sub-gram payloads with milliwatt-scale power budgets. Current secure communication paradigms for these platforms face two critical failure modes:

• Thermodynamic and RF Penalties: Conventional secure protocols (e.g., DTLS, TLS) rely on bidirectional handshakes and persistent non-volatile memory (NVM) for key storage. The energy required for continuous radio frequency (RF) reception and cryptographic handshakes significantly degrades aerial endurance.
• Physical Tampering Vulnerabilities: Sub-gram platforms lack the physical volume to house active tamper-meshes or zeroization batteries. If captured, adversaries can extract persistent cryptographic keys and mission topologies stored in on-board Flash or EEPROM via cold-boot attacks, side-channel analysis, or decapsulation.

2. Methodology

The author proposes a stateless, zero-storage hardware-software co-designed architecture that eliminates persistent on-chip storage entirely ($M_{NVM} = \emptyset$). The system integrates two core technologies:

• Hierarchical Spatiotemporal Key Generation (HSKG):
  Instead of storing keys, the system dynamically reconstructs cryptographic session seeds in $O(1)$ constant time. The key $K_i(t)$ is derived deterministically from real-time physical coordinates $S(t) = [x, y, z, \tau]^T$ and a hardwired, unclonable physical parameter $\Omega$ (derived from gate-oxide mismatch).

  • Mechanism: $K_i(t) = \Phi(S_i(t), \Omega)$, where $\Phi$ is a deterministic mapping operator.
  • Security: Because keys are ephemeral projections of physical state, any deviation from valid spatiotemporal boundaries or power loss immediately renders the key unrecoverable.

• Four-Phase Adiabatic Charge-Recovery Logic (ACRL):
  To minimize computational thermodynamic dissipation, the deterministic engine utilizes sinusoidal ACRL.

  • Mechanism: During the "Recovery" phase, charge stored in load capacitance ($C_L$) is adiabatically driven back into an oscillating resonant tank rather than dumped to ground.
  • Power Clocking: The system employs a 4-phase resonant power clock ($\Phi_1-\Phi_4$) synchronized with the wing actuation and logic evaluation.

• Physical Anti-Tampering Circuit:
  A rapid shunt-to-ground circuit is triggered if the supply voltage drops below a threshold ($V_{cc} < V_{th}$) or if boundary deviation is detected. This drains residual gate charges in volatile flip-flops with a time constant $\tau_{discharge} < 1.2$ ns, collapsing informational entropy to zero instantly.

• Communication Protocol:
  The system enables handshake-free, unidirectional broadcast. Data is encrypted via instantaneous permutation ($C(t) = P_{data} \oplus K_i(t)$) and transmitted without pre-negotiation. Receivers independently reconstruct the key using their own spatiotemporal coordinates and the shared deterministic operator.

3. Key Results

• Energy Efficiency:

  • Computation: Synthesizing a 128-bit key consumes 4.65 µJ, an 81.4% reduction compared to conventional static CMOS (25.0 µJ).
  • Transmission: Wireless transmission overhead is reduced by 79.0% (0.031 mJ/packet vs. 0.148 mJ for lightweight Zigbee/PSK).
  • Latency: Processing time drops to 0.12 ms, and active RF time is reduced to 1.10 ms per packet, eliminating receiver-side power drain ($P_{rx} = 0$).

• Flight Endurance:
  In a simulated 100-mg MAV with a 10-mAh battery:

  • Under high-frequency swarm coordination (10 Hz), conventional DTLS communication reduces flight endurance to 5.2 minutes.
  • The HSKG-ACRL architecture sustains 13.8 minutes of hovering, preserving 93.2% of the theoretical aerodynamic operational ceiling. This represents a 33.0% improvement over lightweight PSK systems and a 165% improvement over conventional DTLS.

• Security:
  Microscopic decapsulation reveals a chemically quiescent substrate with no remanent electric polarizations. The system guarantees that upon capture or power severance, the total informational entropy $H_{total}(t)$ drops to zero, preventing key extraction.

4. Significance and Claims

The paper claims to present the first framework to reconcile extreme SWaP boundaries with physical tamper-resistance in flapping-wing microrobotics. Its primary significance lies in demonstrating that physical persistence can be replaced by spatiotemporal determinism in autonomous swarms.

By discarding the paradigm of persistent storage and bidirectional handshakes, the work resolves the fundamental conflict between high-frequency swarm coordination and energy density. The author asserts that this zero-storage, charge-recovering approach not only secures micro-robots against physical capture but also extends their operational life, making it applicable to entomological robotics, ultra-low-power environmental sensors, and intra-body micro-medical devices operating under strict thermodynamic limits.