Would Briar be a good alternative?
edit: How it works: https://briarproject.org/how-it-works/
edit: How it works: https://briarproject.org/how-it-works/
That said, I am curious to hear more about the offline messaging. If it only is able to exchange when the two people who are trying to communicate with eachother are directly nearby it isn't so much a mesh network, right? A mesh network would be able to route across other nodes to get to its destination. Does Briar do that? The "How it works" page doesn't really seem to answer much, so I am assuming not.
> If the RSSI is below the noise floor, it is impossible to demodulate the signal. However, LoRa can demodulate signals that are below the noise floor.
It's also possible to receive non spread-spectrum signals below the noise floor, if you can observe it over longer time and get additional "processing gain" that way
Additionally, it is a bad idea to use spread spectrum as a means of concealment because if the adversary is physically near enough, your signal will show up above the noise floor. Due to the inverse square law etc, you have a narrow zone of enough power to be received by your remote recipient, but not enough power for closer adversaries to detect you. You are also reliant on the unlikely situation of an adversary without more advanced RF hardware with lower noise receivers.
First, as a definition, below the noise floor means that the power of my signal at any given time is smaller than the power of the ambient noise in my channel, and usually this implies that you're only interested in a particular segment of frequency spectrum (e.g. within the 10MHz band centered at 1.8GHz). If we were doing a simple frequency-shift keying or amplitude-modulated signal, once the noise power exceeds the signal power, there is basically no hope of recovering anything useful, as those are both demodulation schemes that rely upon obtaining instantaneous estimates of the frequency or amplitude of the signal of interest.
However, spread-spectrum methods make a time/frequency tradeoff, where the signal of interest is "spread" across multiple points in time and frequency. A very simple example of this is to say "if I want to transmit a 1, instead of transmitting one cycle of a sinusoid at 18.GHz, I will transmit 10 cycles". Then, at the decoder stage, you average across 10 cycles of your carrier in order to detect whether a signal was sent or not. By doing this averaging across time, you get a 10x gain versus the noise which is expected to cancel itself out as often as not.
True spread-spectrum techniques are more advanced than this, they actually use wave shapes that are more complicated than just a sinusoid to make it easier to detect when they start and stop (whereas with a sinusoid there's a fair amount of ambiguity if you shift one period to the left or right) but the fundamental idea of averaging across time is the same.
Through this mechanism we are able to rescue out signals from far below the noise floor, although it reduces your maximum transmission rate. When dealing with digital radio systems we can even rescue out signals from below our quantization floor, although not too much lower, as eventually you lose the ability to average out a signal that is fluctuating by significantly less than a single bit.
Whenever I talk about making tradeoffs in transmission speed to aid in reception, I am reminded of the ELF systems in submarines [0]. While they did not use spread-spectrum techniques, (they just jumped between two frequencies, 76Hz and 80Hz) they still correlated across time to boost up their effective SNR. [0] https://en.wikipedia.org/wiki/Communication_with_submarines#...
Beyond that though, at this point for protests (in the US at least), the suggested opsec is to leave your phone at home.
Briar actually does set up a meshnet for groups and forums, so long as people are contacts of each other. See the diagram here: https://briarproject.org/img/howitworks3(mobile).svg
There are still holes of course, connecting only to contacts limits the spread of messages but ensures you don't leak too much information if your device is compromised
I continue to be frustrated by having to use the plane's satellite internet connection (not always free) to message somebody sitting two rows away from me, so this would be great.
But, at least in the country I live in, this is excessive for a typical protest burner.
There are so many links in that chain that need to line up, from the manufacturer keeping track of it to the distribution system to keep track of what batch goes where to the vendor keeping track of what phone IMEI is sold when or to who. Even if all those link up you need to get at the video within the rotation time for their video storage or link to their financial transaction data.
I would not be surprised if it is still as easy to evade as shown in the show (and as easy to get wrong).