Glossary

Glossary of Terms

• Anti-Replay Attack: A security mechanism that validates the timestamp of an incoming telemetry packet. QuakeGuard enforces a strict 300-second window (403 on stale) to prevent replay of old earthquake signals.
• Dead Letter Queue (DLQ): Redis Stream readings:dlq (ingest) and List ai_report_queue_dlq (AI) receiving poisoned jobs that fail unrecoverably.
• DeliveryPath: Enum in SerialFallback.h (MQTT, SERIAL_CDC, RETAIN) — pure routing decision of decidePath(mqttReachable, usbHostPresent, timeValid), shared by firmware and host tests.
• DSP (Digital Signal Processing): Manipulation of analog information in digital form. On the ESP32, HPF filtering of ADXL345 readings to remove gravity.
• ECDSA (Elliptic Curve Digital Signature Algorithm): NIST P-256 (secp256r1) via mbedtls, used to prove sensor identity; identical on MQTT and serial planes, re-signed on drain.
• EmergencyReport: Persisted state-machine PENDING → COMPLETED | FAILED for AI reports (see AI Emergency Report Service).
• Geohash Zone Index: Redis fast-path zoneindex:<geohash> (prec 3) for resolve_zone, fallback to PostGIS ST_Contains ordered by ST_Area.
• NVS (Non-Volatile Storage): ESP32 flash storing private key, sensor_id (quake-config), and last-known GNSS fix (quake-gnss).
• Offline Wall Clock: Software clock epochAtSync + millis() anchored at first NTP sync, valid after WiFi drops; no frame emitted before timeValid.
• Ollama: Self-hosted LLM runtime for on-premise emergency reports (v1.2.0).
• PGA (Peak Ground Acceleration): Measure used to estimate magnitude via M = log10(PGA*1.6)+3.0.
• PostGIS: Spatial extender for PostgreSQL; ST_Contains source of truth for zone assignment.
• RetentionRing: Bounded FIFO RetentionRing<100> in SerialFallback.h, overwrites oldest on overflow; drained on path recovery.
• SerialFallback / [QG:FB]: Zero-Trust USB CDC fallback framing SerialFallback.h ([QG:FB]{...}), host bridge serial_bridge.py.
• STA/LTA (Short-Term Average / Long-Term Average): Industry-standard trigger comparing 1 s STA vs 10 s LTA; ratio >1.8 triggers.
• Thundering Herd Problem: Massive synchronous spike from many sensors during a swarm; mitigated via Redis Streams decoupling and per-area cooldown.
• Zero-Trust: All devices continuously validated (ECDSA, API key, anti-replay).

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