This LoRa-Based Mesh Network Turns Raspberry Pi 4 SBCs Into Secure Radio Communication Nodes
Using Ethernet-connected communication nodes, this mesh network promises a secure comms with more than a mile of range.
Semi-pseudonymous engineering student "Thomas" has put together a design for a secure, encrypted communications network powered by Raspberry Pi 4 single-board computers and LoRa radio add-ons — housed in 3D-printed casings and turned into add-ons devices for existing desktops and laptops.
"The goal of this project is to combine the benefits of both centralized and decentralized methods to provide reliable digital communication between users without the need for the internet," Thomas explains. "In addition, this network makes it difficult to track the correspondence between users since these nodes can be used mobily and use pseudo randomly generated identifiers. This network will excel in situations where two parties need to communicate securely and anonymously. This may include civil defense, clandestine operations, and personal communication."
The heart of the system are "nodes," created using Raspberry Pi 4 Model B single-board computers enhanced with an Adafruit LoRa Radio Bonnet working in the 915MHz band. "This was done partly to take advantage of the license-free Industrial, Scientific, and Medical (ISM) frequency bands," Thomas notes, "but also due to the low power requirements and long ranges. Using 5dBi omnidirectional antennas, the receivers can communicate to at least 2km [around 1.24 miles] when they are in line of sight."
While a Raspberry Pi is a fully-functional computer in its own right, that's not how Thomas is using them. Instead, each Raspberry Pi connects to a host system via Ethernet — either directly or by simply existing on the same local network — to act as a gateway to the peer-to-peer encrypted radio network mesh. Data transmitted over the network is encrypted using public-key cryptography, keeping the data within from prying eyes.
Described by Thomas as a "proof of concept," the radio network proved workable — though its creator has suggested a range of potential upgrades from automatic key distribution with congestion avoidance and the option to use alternative encryption and message authentication schemes. Thomas' implementation has also yet to be tested with more than two nodes, one sending and one receiving.
Thomas has released a technical description of the project and an STL file for the Raspberry Pi 4 case on Hackaday.io, but at the time of writing had not yet made the source code publicly available.
