Technical Architecture
How Crisis Connect Works Under the Hood
Crisis Connect is an offline-first emergency communication system that runs entirely on Bluetooth. It enables secure device-to-device messaging and signaling when Internet, cellular networks, or infrastructure are unavailable.
What it does
- Direct phone-to-phone communication (no servers)
- Works with no SIM / no cellular / no Wi-Fi
- End-to-end encryption for message privacy
- Built for disaster conditions and degraded environments
System Goals
Why this architecture exists
Crisis environments break assumptions that normal apps rely on. Crisis Connect is designed around these constraints:
Design Principles
Offline-First
Operates with zero connectivity.
Infrastructure-Free
No servers, relays, or centralized routing.
Low-Energy
BLE for discovery, higher-power transport only when needed.
Secure by Default
End-to-end encryption and integrity protection at the payload level.
High-Level Communication Flow
Presence Broadcasting (BLE): Devices advertise in low power mode
Discovery: Nearby devices detect each other automatically
Link Establishment: A direct peer-to-peer channel is created
Secure Payload Exchange: Encrypted messages travel over the link
No Third Party: No cloud, no server, no intermediaries
The 4-Layer Bluetooth Protocol Stack
Crisis Connect uses a 4-layer stack so each function is isolated and testable.
Layer 4 — Security
privacy + integrity
- Encrypts payload before transmission
- Receiver decrypts locally (no plaintext transit)
- Integrity verification and replay-resistance mechanisms
Layer 3 — Status & Metadata
lightweight attributes for UI/telemetry
- Device ID / session information
- Battery level
- RSSI / signal indicators
- Connection state
Layer 2 — Transport
stable, reliable data channel
- Low-latency 1:1 messaging
- Supports data transfer & offline voice (where enabled)
- Robust behavior under interference compared to best-effort broadcast
Layer 1 — Discovery
fast, low-energy device discovery
- Continuous BLE advertising (no pairing required)
- Rapid detection in proximity-based scenarios
- Supports “immobilized user” cases (device can still broadcast presence)
Message Lifecycle
Zero-Plaintext Transit
User composes a message
Message is encrypted on the sender device
Encrypted payload is sent via RFCOMM
Receiver decrypts locally
Plaintext never leaves the device
SOS & Rescue Mode
Crisis Connect includes a dedicated SOS mechanism designed for discovery and field response.
Signal
- Device continuously emits BLE SOS presence
- Field teams can detect nearby signals using RSSI patterns
Contact
- Once detected, a direct link can be established for two-way communication
- Enables teams to confirm status, needs, and priority without infrastructure
Energy Strategy
- BLE handles discovery in low power mode
- Transport channels activate only when necessary
- No background Internet polling
- No cloud sync loops
Outcome: maximized operational time on limited battery
Why Bluetooth-Only?
Intentional tradeoff
Crisis Connect avoids Wi-Fi Direct / hotspots / cellular fallback by design to keep:
Limitations & Operational Reality
- Range varies by device and environment
- Dense concrete/metal can reduce performance
- Bluetooth is proximity-based by nature
Crisis Connect is **not a replacement** for cellular networks. It is a **last-resort communication layer** designed for the moment when networks fail.
Intended Use Cases
- Earthquake response and rubble scenarios
- Search & rescue field operations
- Infrastructure collapse / network outage
- Remote and off-grid missions
For Developers & Institutions
- Designed for field deployment and controlled evaluation
- Suitable for emergency services & government use
- Can be tested with scenario-based protocols
- Documentation and test packs available upon request