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Encrypted LoRa Radio + Passive Sensing

Communicate When Networks Fail

GridDown Secure Messenger is an encrypted LoRa communications system with built-in 900 MHz drone scanning, acoustic gunshot detection, and RF jamming countermeasures. AES-256-GCM encryption. Codec2 voice. Mesh relay. No infrastructure required.

Get the Hardware → Flash Firmware View Capabilities

AES-256

Encryption

902–928

MHz ISM Band

4-Hop

Mesh Relay

52 Ch

Drone Scanner

Explore

Zero Infrastructure Communications + Passive Sensing

GridDown Secure Messenger operates entirely over LoRa radio on the 902–928 MHz ISM band — no cell towers, no internet, no satellites. End-to-end encrypted messaging and voice with the same radio hardware simultaneously performing passive RF scanning and acoustic monitoring. All cryptographic operations run on-device using the ESP32-S3's hardware-accelerated mbedTLS. PSK encrypted at rest with device-specific XOR wrapping. No cloud, no accounts, no external dependencies.

Hardware

T-Deck CYPHER M8K

Built-in keyboard, display, GPS, LoRa radio, and microphone in a compact handheld form factor.

Two GridDown Secure Messenger units showing the GridDown Radio main dashboard with mesh network status, RF scanning, and navigation controls

GridDown Secure Messenger showing encrypted voice recording interface and 900 MHz drone scanner spectrum display

Core Capabilities

More Than a Radio

The radio hardware does triple duty — encrypted communications, passive RF sensing, and acoustic detection — from a single device in your pack.

E2E

Core

Encrypted Messaging

Dual-Layer Encryption over LoRa

Two independent encryption layers. Group PSK: PBKDF2-HMAC-SHA256 derived AES-256-GCM key (10,000 iterations) encrypts all traffic. E2E direct messages: ephemeral ECDH P-256 key exchange auto-negotiated via beacons, with per-boot forward secrecy. All crypto runs on-device via mbedTLS. PSK encrypted at rest with device-specific wrapping.

ECDH P-256 PBKDF2 AES-256-GCM Forward Secrecy

VOX

Core

Voice over LoRa

Codec2 — Three Voice Modes

Voice messages captured from the onboard ES7210 quad-channel I2S microphone, compressed with Codec2 (1600 or 3200 bps), encrypted, fragmented into LoRa-sized packets, and reassembled on the receiving end. Three modes: Range (1600 bps, 2× redundancy), Balanced (3200 bps, 2× redundancy), Clarity (3200 bps, single pass). Record, preview, send — with full DSP pipeline including AGC, noise gate, biquad IIR filtering, and pre/de-emphasis. Cross-mode interoperability — receivers auto-detect.

Codec2 1600/3200 ES7210 ADC Preview Before Send 3 Quality Modes

FHSS

Core

Channel Hopping

Frequency-agile transmission

8 channels across the 902–928 MHz ISM band (2.5 MHz spacing) with pseudorandom hop sequences derived from the shared group PSK. GPS-synchronized 30-second hop slots — all radios with the same PSK and GPS lock hop in unison. Without the group key, an observer sees random encrypted packets on random frequencies. Requires GPS position lock to activate — radios without GPS stay on their configured base channel.

8 Channels GPS-Synced 30s Slots PSK-Derived Sequence Auto-Fallback

SCAN

Sensor

900 MHz Drone Scanner

Passive RF detection on the ISM band

The SX1262 LoRa transceiver does double duty as a passive 900 MHz RF scanner. Sweeps 52 channels across 902–928 MHz in 500 kHz steps using dual-mode detection — LoRa CAD for preamble detection and RSSI energy detection for non-LoRa signals. Classifies ELRS, Crossfire, SiK/RFD900, and separates drones from LoRaWAN infrastructure.

52 Channels CAD + RSSI 4 Scan Profiles RF Baseline

ACOU

Sensor

Gunshot Detection

Acoustic impulsive transient detector

Background acoustic monitoring via the ES7210 microphone. Pure DSP — no ML models. Detects impulsive transients with rise time < 1ms, peak amplitude 6–20× above an adaptive noise floor, and multi-sample confirmation (3–5 hits within 150–200ms). Wind and engines raise the noise floor gradually and don't trigger. GPS-tagged detections broadcast over LoRa automatically.

3 Sensitivity Levels Adaptive Noise Floor GPS Tagged Auto LoRa Alert

JAM

Security

Jamming Detection

Coordinated channel migration

Continuous noise floor monitoring on the active messaging channel. If sustained energy 20+ dB above baseline is detected for 10 seconds, the system confirms jamming and initiates coordinated channel migration — all radios in the group switch to the quietest available frequency simultaneously. Adaptive baseline rejects gradual environmental changes. Voice activity automatically suppresses detection to prevent false triggers during TX/RX.

20 dB Threshold Auto-Migrate Coordinated Switch Adaptive Baseline

MESH

Core

Mesh Relay

Multi-hop range extension

Messages automatically relay through intermediate radios to extend range across a team. Up to 4 hops for text messages, 2 hops for voice. Hash-based deduplication prevents relay storms. Store-and-forward queues messages for offline peers and delivers automatically when they come back into range.

4-Hop Text 2-Hop Voice Store & Forward Deduplication

EMER

Security

Duress & Remote Wipe

Covert distress + authenticated erasure

Covert duress signaling — a silent distress flag embedded in normal messages that alerts teammates without the captor's knowledge, with GPS coordinates when available. Authenticated remote wipe erases a device via HMAC-signed, PSK-encrypted command with GPS-synced replay protection.

Silent Duress Remote Wipe HMAC Signed Replay Protected

Core

Standalone Operation

Full UI on the radio hardware

The radio operates independently with a built-in display, keyboard, and trackball. Peer-threaded conversations, group broadcast ACK (per-peer delivery tracking), canned messages, 4 group channels, channel scan on boot, WiFi QR code display, calibrated battery monitoring, WCAG-compliant button contrast, and a hold-to-activate emergency broadcast from any screen including lock. Three WiFi modes (AP/STA/OFF) with mDNS discovery and zero-touch credential push from the tablet.

TFT Display WiFi AP/STA/OFF BLE + WiFi Bridge GPS Onboard

TAK

Core

TAK / CoT Bridge

Cursor-on-Target integration

Bidirectional Cursor-on-Target bridge with four output modes: OFF, Multicast (UDP 239.2.3.1:6969), TCP (configurable TAK server), and All. Triple output paths: WebSocket to GridDown PWA, UDP multicast to ATAK, TCP to TAK server. Inbound CoT events converted to peers, tracks, and waypoints. Duress alerts forwarded as TAK events with GPS coordinates.

ATAK Multicast TCP TAK Server Bidirectional Duress → CoT

WPT

Core

Tactical Waypoints

Shared markers across the mesh

Named waypoints shared via 4-hop mesh relay and persisted to device storage. Quick-drop from map screen, compose command (/wp Name), or tablet push. 6 icon types for different marker purposes. Waypoints appear on all peer devices and on the GridDown PWA map.

4-Hop Shared 6 Icon Types Quick Drop Persistent

PROX

Sensor

Threat Proximity Alerts

Configurable perimeter warnings

Automatic warnings when situational awareness tracks enter a configurable radius (500m to 10km). Displays bearing, distance, and altitude trend. 30-second cooldown prevents alert fatigue. Integrates with drone scanner detections and peer tracking data.

500m – 10km Bearing + Distance Cooldown Auto Alert

BOOT

Core

Channel Scan on Boot

Find your team instantly

Automatic 8-channel CAD + RSSI sweep on every startup (~5 seconds). 10 CAD probes at SF10/BW125 plus 5-sample median RSSI per channel. Active channels highlighted in green with hit counts. Operators joining late or recovering from a reboot can immediately see which channel their team is on.

Auto on Boot 8 Channels CAD + RSSI ~5 Seconds

ACK

Core

Group Broadcast ACK

Per-peer delivery confirmation

Broadcast messages track per-peer delivery with lightweight ACK packets and jittered transmission to avoid collisions. 16-bit bitmask dedup prevents double-counting. Display shows confirmed/total (e.g., 3/5) with color coding: grey = none, yellow = partial, green = all confirmed. Supports up to 16 peers.

Per-Peer Tracking Collision Jitter 16 Peers Max Color Status

WiFi

Core

WiFi Connectivity

Three operating modes + mDNS discovery

AP mode creates a standalone network (scan QR to join). STA mode joins your tablet hotspot for a unified network with the Pi 5 Sensor Hub. OFF mode disables WiFi entirely for maximum battery life. mDNS registers as griddown-radio.local in STA mode. Zero-touch credential push from the tablet via WebSocket — operator confirms on-device before switching. QR code display adapts to the active mode.

AP / STA / OFF mDNS Discovery WiFi QR Code Credential Push

900 MHz Scanner

Four Scan Profiles

The scanner detects drone control and telemetry links across the 902–928 MHz ISM band. Each profile trades speed for depth depending on the operational need.

Quick LoRa

CAD Only — Fastest Sweep

LoRa preamble detection at SF6/BW500. Catches ELRS and Crossfire control links in seconds. Best for rapid situational checks — "is anything hopping on 900 MHz right now?"

All Drone

CAD + RSSI + Dual-BW — Default

Combined LoRa CAD and energy detection with dual-bandwidth discrimination. Catches both LoRa-based (ELRS, Crossfire) and non-LoRa (SiK, RFD900, Holybro) control links. Automatically separates drones from LoRaWAN infrastructure.

Full Spectrum

RSSI Only — Wideband Energy

Pure energy detection across all 52 channels. No protocol assumptions — detects any signal above the noise floor. Useful for general RF environment characterization.

ELRS Deep

Multi-SF CAD — SF5 Through SF8

Cycles through spreading factors 5–8 to catch all ELRS rate configurations (50Hz through 500Hz). Slower but catches long-range ELRS links that Quick LoRa misses at higher spreading factors.

Technical Specifications

Under the Hood

Radio

TransceiverSX1262 LoRa

Frequency902–928 MHz ISM

Channels8 (messaging) / 52 (scan)

TX PowerUp to +22 dBm

ModulationLoRa (SF5–SF12)

Bandwidth125 / 250 / 500 kHz

Encryption

Key AgreementECDH P-256 (ephemeral)

Group PSKPBKDF2 (10K iterations)

Message CipherAES-256-GCM

Delivery AuthHMAC-SHA256 signed ACK

Crypto LibrarymbedTLS (ESP-IDF)

Key StorageOn-device (XOR-wrapped)

Voice

CodecCodec2 1600 / 3200

ModesRange / Balanced / Clarity

MicrophoneES7210 4-ch I2S

DSPAGC, noise gate, IIR, pre-emph

WorkflowRecord → Preview → Send

Relay2-hop mesh, auto-detect codec

Drone Scanner

Band902–928 MHz

Channels52 (500 kHz steps)

DetectionCAD + RSSI dual-mode

ProfilesQuick / All / Full / Deep

TargetsELRS, Crossfire, SiK, RFD900

FilteringInfrastructure rejection

Acoustic

MethodImpulsive transient DSP

Rise Time< 1 ms trigger

Threshold6–20× noise floor

Confirmation3–5 hits / 150–200 ms

SensitivityHigh / Med / Low

AlertGPS + auto LoRa broadcast

Platform

MCUESP32-S3 (240 MHz, 8MB PSRAM)

GPSu-blox M8K GNSS

Display2.8" IPS ST7789 (320×240)

InputKeyboard + Trackball

WiFiAP / STA / OFF + mDNS

BLENimBLE Nordic UART Service

Storage16MB Flash + microSD

Firmware~14,800 lines C++

Part of the GridDown platform

GridDown Secure Messenger integrates with GridDown — the offline tactical navigation and situational awareness platform. Drone scanner tracks appear on the GridDown map. Gunshot alerts share GPS coordinates across the team. Encrypted messages flow through the same interface as your maps, waypoints, and weather.

Get the T-Deck CYPHER M8K → Flash Firmware GridDown Platform

The GridDown Secure Messenger firmware is free. Hardware is sold by Rokland via an affiliate link — we may earn a commission at no additional cost to you. Already have a T-Deck CYPHER M8K? Use the web flasher to install the firmware directly from your browser.

Encryption Architecture

✓ Dual-layer: Group PSK + E2E ECDH P-256
✓ AES-256-GCM message encryption
✓ Per-boot forward secrecy on DMs
✓ HMAC-SHA256 signed delivery confirmations
✓ PSK encrypted at rest (device-specific wrap)
✓ All crypto on-device via mbedTLS

Operational Security

✓ Frequency hopping resists interception
✓ Jamming detection with auto-migration
✓ Covert duress signaling
✓ Authenticated remote device wipe
✓ Replay-protected commands (GPS-synced)
✓ No accounts, no registration, no cloud

Passive Sensing

✓ 900 MHz drone scanner — receive only
✓ Acoustic gunshot detection — listen only
✓ No transmission during scanning
✓ Infrastructure vs. drone classification
✓ RF baseline delta detection
✓ Detections pushed to GridDown map

Important Legal Disclaimers

RADIO REGULATIONS: GridDown Secure Messenger operates in the 902–928 MHz ISM band. Users are solely responsible for compliance with all applicable radio frequency regulations in their jurisdiction, including FCC Part 15 (USA), IC RSS-210 (Canada), and equivalent regulations elsewhere. ISM band operation does not require a license in most jurisdictions, but power limits and duty cycle restrictions apply.

NOT A SAFETY SYSTEM: The 900 MHz drone scanner, acoustic gunshot detection, and RF jamming detection features are for INFORMATIONAL PURPOSES ONLY. They are not certified detection systems and may produce false positives or miss real threats. Do not rely on these features for safety-critical decisions. Professional equipment and training are required for security applications.

ENCRYPTION NOTICE: This product incorporates cryptographic functionality. Export, re-export, and use of cryptographic products may be subject to regulation in your jurisdiction. Users are responsible for compliance with all applicable export control and encryption laws.

WARRANTY: GridDown Secure Messenger software is provided "AS IS" without warranty of any kind. The T-Deck CYPHER M8K hardware carries its original manufacturer's warranty. BlackAtlas warrants proper firmware installation and configuration for 30 days from delivery. See Terms of Service and Full Disclaimer for complete details.