GlossaryElectric Aircraft Battery Cybersecurity Glossary
Each term follows the same pattern: definition, why it matters, a practical example, and how to verify it.
- BMS (Battery Management System)
- The embedded controller that monitors cell/pack state and enforces safe charge, discharge, and thermal limits.
- Why it matters: It is the central trust broker between the physical battery and every aircraft system that consumes energy data or issues power commands.
- Example: The BMS estimates SOC from voltage and coulomb counting, then commands contactors open if a cell exceeds a safe voltage limit.
- Verification: Verify BMS firmware version and configuration hash against a signed baseline before flight.
- EMS (Energy Management System)
- The aircraft-level system that converts BMS state into an overall energy and power-availability picture for mission and flight-phase decisions.
- Why it matters: It is where battery-level trust becomes aircraft-level trust — errors or manipulation upstream propagate into flight planning through the EMS.
- Example: The EMS combines BMS SOC with known flight-phase power demand to estimate remaining flight time.
- Verification: Cross-check EMS-reported remaining energy against an independently derived estimate.
- SOC (State of Charge)
- The percentage of usable energy remaining in a battery relative to its full capacity.
- Why it matters: SOC is the primary input to remaining-flight-time and reserve-margin decisions; a falsified SOC directly misrepresents available energy.
- Example: A pack reporting 40% SOC that has actually degraded to an effective 30% usable capacity overstates real reserve.
- Verification: Cross-check SOC trend against coulomb counting and recent current draw for physical plausibility.
- SOH (State of Health)
- An estimate of a battery's remaining capacity and performance relative to its original, new condition.
- Why it matters: SOH informs maintenance and dispatch decisions; a falsified SOH can mask genuine degradation or trigger unnecessary grounding.
- Example: A pack with declining SOH trend across cycles indicates approaching end-of-useful-life sooner than its rated cycle count would suggest.
- Verification: Compare SOH trend against cycle count, thermal history, and peer-pack behavior.
- PDU (Power Distribution Unit)
- The component that routes electrical power from the battery/contactors to inverters and other loads under vehicle control unit authority.
- Why it matters: It sits directly in the path between energy-trust decisions and physical power delivery to propulsion.
- Example: The PDU distributes power to each motor controller according to VCU-issued power allocation.
- Verification: Confirm PDU only executes power-routing commands from an authenticated, authorized source.
- Trust Boundary
- A point in the architecture where data or commands cross between components or actors with different levels of assumed trust.
- Why it matters: Threat modelling focuses effort at trust boundaries, since that is where verification is most needed and most valuable.
- Example: The charging interface is a trust boundary between ground charging equipment and the aircraft's battery pack.
- Verification: Enumerate every trust boundary in the architecture diagram and confirm each has an explicit verification control.
- Attack Surface
- The complete set of entry points through which a system could potentially be reached by an attacker.
- Why it matters: Understanding the attack surface is the starting point for prioritising which entry points need the strongest controls.
- Example: The OTA update channel, ground diagnostic port, and charging interface together form part of the battery system's attack surface.
- Verification: Maintain an inventory of entry points and confirm each is mapped to at least one detection or mitigation control.
- Threat Model
- A structured analysis of a system's assets, entry points, threats, and consequences, used to prioritise security effort.
- Why it matters: It turns an open-ended security question into a concrete, reviewable artifact that engineering and safety teams can act on.
- Example: The threat catalogue on this page is a threat model expressed as individual threat cards mapped to components and controls.
- Verification: Review the threat model against the actual as-built architecture, not only the intended design.
- Secure Boot
- A boot process that cryptographically verifies firmware authenticity before allowing it to execute.
- Why it matters: It prevents a controller from running tampered or unsigned firmware, closing off a high-consequence attack path.
- Example: A BMS with secure boot refuses to execute a firmware image that does not match its expected signature.
- Verification: Attempt to boot an unsigned or altered firmware image in a test environment and confirm it is rejected.
- OTA (Over-the-Air Update)
- A firmware or configuration update delivered to a controller over a wireless or network channel rather than a physical connection.
- Why it matters: OTA channels can reach many aircraft at once, giving a compromised update pipeline unusually wide blast radius.
- Example: An OTA campaign updates BMS firmware across a fleet to add a new detection rule.
- Verification: Confirm every update package is signed, version-monotonic, and independently verified by the receiving controller.
- Replay Attack
- An attack that retransmits a previously valid, captured message to produce a misleading effect at a later time.
- Why it matters: Without freshness checks, a captured 'everything is normal' telemetry burst can be replayed to mask a real abnormal condition.
- Example: A captured normal-temperature telemetry sequence is replayed during an actual thermal excursion.
- Verification: Replay a captured message in a test environment and confirm a freshness/sequence check causes it to be rejected.
- Energy Margin
- The difference between the energy and power the aircraft is estimated to have and the energy and power actually required for the remainder of the mission plus contingency.
- Why it matters: This is the quantity a cyberattack most directly threatens: a falsely inflated energy margin can leave insufficient real reserve.
- Example: A trustworthy energy margin accounts for the current flight phase, a contingency allowance, and a safe-landing reserve.
- Verification: Compare the primary energy-margin estimate against an independently derived one and require agreement within a defined tolerance.
- Degraded Mode
- A defined, bounded operating state the aircraft enters when trust in a component or data source is lost, rather than continuing to act on untrusted data.
- Why it matters: Detection without a defined degraded-mode response can leave the aircraft in an undefined state, which is itself a risk.
- Example: On loss of trust in primary SOC telemetry, the aircraft falls back to a conservative, independently derived energy estimate.
- Verification: Trigger the loss-of-trust condition in a test environment and confirm the aircraft enters the documented degraded mode.
- Cyber Range
- A controlled, instrumented environment used to simulate attacks and test detection/response without risk to real aircraft or hardware.
- Why it matters: It allows threat scenarios and detection rules to be validated safely before any onboard deployment.
- Example: A battery telemetry cyber range replays injected and spoofed messages against a BMS simulation to validate detection rules.
- Verification: Confirm each threat-catalogue entry has at least one corresponding cyber-range test case.
- Cryptographic Agility
- The ability to change cryptographic algorithms or key sizes used by a system without a full hardware redesign.
- Why it matters: Aerospace systems are long-lived; cryptographic agility is what allows a future algorithm transition (including post-quantum) without stranding fielded hardware.
- Example: A signature-verification module designed to support algorithm updates through a firmware change rather than new hardware.
- Verification: Confirm the cryptographic implementation is abstracted behind an interface that does not hard-code a single algorithm.