cc @mc-hamster. In some cases storeForwardPluginRadio can be null ;-)
~/development/meshtastic/meshtastic-esp32$ bin/exception_decoder.py -e .pio/build/tbeam/firmware.elf ex
stack:
0x401db467: StoreForwardPluginRadio::sendPayload(unsigned int, bool) at /home/kevinh/development/meshtastic/meshtastic-esp32/src/plugins/esp32/StoreForwardPlugin.cpp:235
0x400e7cbd: StoreForwardPlugin::runOnce() at /home/kevinh/development/meshtastic/meshtastic-esp32/src/plugins/esp32/StoreForwardPlugin.cpp:225
0x400d4cca: concurrency::OSThread::run() at /home/kevinh/development/meshtastic/meshtastic-esp32/src/concurrency/OSThread.cpp:45
0x400f015d: ThreadController::runOrDelay() at /home/kevinh/development/meshtastic/meshtastic-esp32/.pio/libdeps/tbeam/Thread/ThreadController.cpp:153
0x400da070: loop() at /home/kevinh/development/meshtastic/meshtastic-esp32/src/main.cpp:621
0x400ff709: loopTask(void*) at /home/kevinh/.platformio/packages/framework-arduinoespressif32/cores/esp32/main.cpp:19
Signed-off-by: Kevin Hester <kevinh@geeksville.com>
Instead of holding onto only the last measurement, hold onto a copy of the last MeshPacket containing a measurement
This will make it easier to display the last time received
make DHT sensor reads more reliable
user preference for Farenheit vs Celsius
specifying a tag/commit/etc (I haven't tried specifying a branch?)
Without specifying the hash, the build breaks for anyone who already had
a repo (the CI build doesn't see this because it always pulls from scratch)
cc @crossan007 & @mc-hamster
@mc-hamster seems to work pretty good for me, so I'll send a PR to you
for the dev-http branch.
I'll push out an android alpha build later today (once the build is
complete). Once this new device load is out in the field _future_
device builds will support updating spiffs from android. (i.e. device
loads older than 1.1.9 must be updated to 1.1.9 or later before spiffs
support is implemented on the device side - so some users might need to
update twice before the new spiffs contents will appear on their device)
Typo fixed. I placed the latest javascript library files into the static folder. Updated the root file handler to be able to serve both compressed and uncompressed files.
+ // NOTE: The phone app needs to know the ls_secs value so it can properly expect sleep behavior.
+ // So even if we internally use 0 to represent 'use default' we still need to send the value we are
+ // using to the app (so that even old phone apps work with new device loads).
+#define MAX_POWER 27
// if we use 20 we are limited to 1% duty cycle or hw might overheat. For continuous operation set a limit of 17
+// In theory up to 27 dBm is possible, but the modules installed in most radios can cope with a max of 20. So BIG WARNING
+// if you set power to something higher than 17 or 20 you might fry your board.
# Can optionally take parameters from the github UI, more info here https://github.blog/changelog/2020-07-06-github-actions-manual-triggers-with-workflow_dispatch/#:~:text=You%20can%20now%20create%20workflows,the%20workflow%20is%20run%20on.
# workflow_dispatch:
# inputs:
# Only want to be run if a new tag starting with v is pushed.
push:
branches:
- "!*"
tags:
- "v*"
jobs:
build:
runs-on:ubuntu-latest
steps:
- name:Checkout code
uses:actions/checkout@v2
with:
submodules:'recursive'
# get github branch and tag names as ${{ steps.branch_name.outputs.SOURCE_TAG }}
inexpensive GPS mesh radios as an extensible, super long battery life mesh GPS communicator. These radios are great for hiking, skiing, paragliding -
inexpensive GPS mesh radios as an extensible, super long battery life mesh GPS communicator. These radios are great for hiking, skiing, paragliding -
essentially any hobby where you don't have reliable internet access. Each member of your private mesh can always see the location and distance of all other
essentially any hobby where you don't have reliable internet access. Each member of your private mesh can always see the location and distance of all other
members and any text messages sent to your group chat.
members and any text messages sent to your group chat.
@@ -30,11 +30,14 @@ We currently support three models of radios.
- [T-Beam V0.7 w/ NEO-6M](https://www.aliexpress.com/item/4000574335430.html) (will work but **you must use the tbeam0.7 firmware ** - but the T-Beam V1.0 or later are better!)
- [T-Beam V0.7 w/ NEO-6M](https://www.aliexpress.com/item/4000574335430.html) (will work but **you must use the tbeam0.7 firmware ** - but the T-Beam V1.0 or later are better!)
Note: The GPS and LoRa stock antennas should be placed in a way, that the GPS antenna faces the sky and the LoRa antenna radiates 360 degrees horizontally. For better GPS reception you might want to [upgrade the GPS antenna](https://meshtastic.discourse.group/t/the-importance-of-gps-antennas-and-request-to-3d-case-documentation-people/1505) and to properly align the antennas you might want to upgrade to a LoRa antenna that can be adjusted to radiate into the right directions.
**Make sure to get the frequency for your country**
**Make sure to get the frequency for your country**
@@ -193,7 +199,7 @@ We'd love to have you join us on this merry little project. Please see our [deve
# Credits
# Credits
This project is run by volunteers. Past contributors include:
This project is run by volunteers. We are a friendly group and welcome any contribution (code fixes, documentation, features, bug reports etc...). We try to be good about listing contributor names in release notes, but it has become unwieldy for the main-devs to keep updating the list below and we've neglected it too long. If you'd like your name included in this list please send a pull request to edit this README and simply add your line yourself. Thank you very much for your help!
-@astro-arphid: Added support for 433MHz radios in europe.
-@astro-arphid: Added support for 433MHz radios in europe.
-@claesg: Various documentation fixes and 3D print enclosures
-@claesg: Various documentation fixes and 3D print enclosures
inexpensive (\$30 ish) GPS radios as an extensible, long battery life, secure, mesh GPS communicator. These radios are great for hiking, skiing, paragliding - essentially any hobby where you don't have reliable internet access. Each member of your private mesh can always see the location and distance of all other members and any text messages sent to your group chat.
The radios automatically create a mesh to forward packets as needed, so everyone in the group can receive messages from even the furthest member. The radios will optionally work with your phone, but no phone is required.
Note: Questions after reading this? See our new [forum](https://meshtastic.discourse.group/).
### Uses
- Outdoor sports where cellular coverage is limited. (Hiking, Skiing, Boating, Paragliding, Gliders etc..)
- Applications where closed source GPS communicators just won't cut it (it is easy to add features for glider pilots etc...)
- Secure long-range communication within groups without depending on cellular providers
- Finding your lost kids ;-)
- Through our [python API](https://pypi.org/project/meshtastic/) use these inexpensive radios to easily add mesh networking to your own projects.
[](https://www.youtube.com/watch?v=WlNbMbVZlHI "Meshtastic early demo")
### Features
Not all of these features are fully implemented yet - see **important** disclaimers below. But they should be in by the time we decide to call this project beta (three months?)
- Very long battery life (should be about eight days with the beta software)
- Built in GPS and [LoRa](https://en.wikipedia.org/wiki/LoRa) radio, but we manage the radio automatically for you
- Long range - a few miles per node but each node will forward packets as needed
- Secure - channels are encrypted by AES256 (But see important disclaimers below wrt this feature)
- Shows direction and distance to all members of your channel
- Directed or broadcast text messages for channel members
- Open and extensible codebase supporting multiple hardware vendors - no lock in to one vendor
- Communication API for bluetooth devices (such as our Android app) to use the mesh. An iOS application is in the works. And [Meshtastic-python](https://pypi.org/project/meshtastic/) provides access from desktop computers.
- Very easy sharing of private secured channels. Just share a special link or QR code with friends and they can join your encrypted mesh
This project is currently in beta testing but it is fairly stable and feature complete - if you have questions please [join our discussion forum](https://meshtastic.discourse.group/).
This software is 100% open source and developed by a group of hobbyist experimenters. No warranty is provided, if you'd like to improve it - we'd love your help. Please post in the [forum](https://meshtastic.discourse.group/).
### Beginner's Guide
For an detailed walk-through aimed at beginners, we recommend [meshtastic.letstalkthis.com](https://meshtastic.letstalkthis.com/).
# Updates
Note: Updates are happening almost daily, only major updates are listed below. For more details see our forum.
- 09/14/2020 - 1.0.0 Now with over 1700 android users, over 2000 nodes and translated into 15 languages. This project will always be a "beta" experiment, but now quite usable. We are currently selecting 1.1 features in our discussion forum.
- 06/24/2020 - 0.7.x Now with over 1000 android users, over 600 people using the radios and translated into 22 languages. Fairly stable and we are working through bugs to get to 1.0.
- 06/04/2020 - 0.6.7 Beta releases of both the application and the device code are released. Features are fairly solid now with a sizable number of users.
- 04/28/2020 - 0.6.0 [Python API](https://pypi.org/project/meshtastic/) released. Makes it easy to use meshtastic devices as "zero config / just works" mesh transport adapters for other projects.
- 04/20/2020 - 0.4.3 Pretty solid now both for the android app and the device code. Many people have donated translations and code. Probably going to call it a beta soon.
- 03/03/2020 - 0.0.9 of the Android app and device code is released. Still an alpha but fairly functional.
- 02/25/2020 - 0.0.4 of the Android app is released. This is a very early alpha, see below to join the alpha-testers group.
- 02/23/2020 - 0.0.4 release. Still very bleeding edge but much closer to the final power management, a charged T-BEAM should run for many days with this load. If you'd like to try it, we'd love your feedback. Click [here](https://github.com/meshtastic/Meshtastic-esp32/blob/master/README.md) for instructions.
- 02/20/2020 - Our first alpha release (0.0.3) of the radio software is ready brave early people.
## Meshtastic Android app
Our Android application is available here:
[](https://play.google.com/store/apps/details?id=com.geeksville.mesh&referrer=utm_source%3Dgithub-homepage)
The link above will return older more stable releases. We would prefer if you join our alpha-test group, because the application is rapidly improving. Three steps to opt-in to the alpha- test:
1. Join [this Google group](https://groups.google.com/forum/#!forum/meshtastic-alpha-testers) with the account you use in Google Play.
2. Go to this [URL](https://play.google.com/apps/testing/com.geeksville.mesh) to opt-in to the alpha test.
3. If you encounter any problems or have questions, post in our [forum](https://meshtastic.discourse.group/) and we'll help.
If you'd like to help with development, the source code is [on github](https://github.com/meshtastic/Meshtastic-Android).
The app is also distributed for Amazon Fire devices via the Amazon appstore: [](https://www.amazon.com/Geeksville-Industries-Meshtastic/dp/B08CY9394Q)
## Supported hardware
We currently support two brands of radios. The [TTGO T-Beam](https://www.aliexpress.com/item/4001178678568.html) and the [Heltec LoRa 32](https://heltec.org/project/wifi-lora-32/). Most people should buy the T-Beam and a 18650 battery (total cost less than \$35). Also, the version of the T-Beam we link to is shipped with Meshtastic **preinstalled** by TTGO, so you don't have to install it yourself.
Make sure to buy the frequency range which is legal for your country. For the USA, you should buy the 915MHz version. Getting a version that include a screen is optional, but highly recommended.
Instructions for installing prebuilt firmware can be found [here](https://github.com/meshtastic/Meshtastic-esp32/blob/master/README.md).
For a nice looking cases:
- 3D printable cases
1. TTGO T-Beam V0 see this [design](https://www.thingiverse.com/thing:3773717) by [bsiege](https://www.thingiverse.com/bsiege).
2. TTGO T_Beam V1 (SMA) see this [design](https://www.thingiverse.com/thing:3830711) by [rwanrooy](https://www.thingiverse.com/rwanrooy) or this [remix](https://www.thingiverse.com/thing:3949330) by [8ung](https://www.thingiverse.com/8ung)
3. TTGO T_Beam V1 (IPEX) see this [design](https://www.thingiverse.com/thing:4587297) by [drewsed](https://www.thingiverse.com/drewsed)
4. Heltec Lora32 see this [design](https://www.thingiverse.com/thing:3125854) by [ornotermes](https://www.thingiverse.com/ornotermes).
- Laser-cut cases
1. TTGO T_Beam V1 (SMA) see this [design](https://www.thingiverse.com/thing:4552771) by [jefish](https://www.thingiverse.com/jefish)
# IMPORTANT DISCLAIMERS AND FAQ
For a listing of currently missing features and a FAQ click [here](faq.md).
This project is still pretty young but moving at a pretty good pace. Not all features are fully implemented in the current alpha builds.
Most of these problems should be solved by the beta release (within three months):
- We don't make these devices and they haven't been tested by UL or the FCC. If you use them you are experimenting and we can't promise they won't burn your house down ;-)
- The encryption implementation is good but see this list of [caveats](software/crypto.md#summary-of-strengthsweaknesses-of-our-current-implementation) to determine risks you might face.
- A number of (straightforward) software work items have to be completed before battery life matches our measurements, currently battery life is about three days. Join us on chat if you want the spreadsheet of power measurements/calculations.
- The Android API needs to be documented better
- No one has written an iOS app yet. But some good souls [are talking about it](https://github.com/meshtastic/Meshtastic-esp32/issues/14) ;-)
For more details see the [device software TODO](https://github.com/meshtastic/Meshtastic-esp32/blob/master/docs/software/TODO.md) or the [Android app TODO](https://github.com/meshtastic/Meshtastic-Android/blob/master/TODO.md).
# FAQ
If you have a question missing from this faq, please [ask in our discussion forum](https://meshtastic.discourse.group/). And if you are feeling extra generous send in a pull-request for this faq.md with whatever we answered ;-).
## Q: Which of the various supported radios should I buy?
Basically you just need the radio + (optional but recommended) battery. The TBEAM is usually better because it has gps and huge battery socket. The Heltec is basically the same hardware but without the GPS (the phone provides position data to the radio in that case, so the behavior is similar - but it does burn some battery in the phone). Also the battery for the Heltec can be smaller.
In addition to Aliexpress, (banggood.com) usually has stock and faster shipping, or Amazon. If buying a TBEAM, make sure to buy a version that includes the OLED screen - this project doesn't absolutely require the screen, but we use it if is installed.
@claesg has added links to various 3D printable cases, you can see them at (www.meshtastic.org).
## Q: Do you have plans to commercialize this project
Nope. though if some other person/group wanted to use this software and a more customized device we think that would be awesome (as long as they obey the GPL license).
## Q: Does this project use patented algorithms?
(Kindly borrowed from the geeks at [ffmpeg](http://ffmpeg.org/legal.html))
We do not know, we are not lawyers so we are not qualified to answer this. Also we have never read patents to implement any part of this, so even if we were qualified we could not answer it as we do not know what is patented. Furthermore the sheer number of software patents makes it impossible to read them all so no one (lawyer or not) could answer such a question with a definite no. We are merely geeks experimenting on a fun and free project.
We don't collect any personal identifying information.
If you have opted-in to analytics (thank you - that helps us know what things we need to improve), we'll receive anonymized information about user behavior. i.e. which screens you used in the app etc... We never
capture usernames, the contents of your texts or your location.
This is an open-source project run by hobbyists and we try to be completely transparent. If you have questions on this policy, please file [a github issue](https://github.com/meshtastic/meshtastic-esp32/issues) and we'll reply/clarify/correct.
We use the same channel maps as LoRaWAN (though this is not LoRaWAN).

See [this site](https://www.rfwireless-world.com/Tutorials/LoRa-channels-list.html) for more information.
## LoRaWAN Europe Frequency Band
The maximum power allowed is +14dBM.
### 433 MHz
There are eight channels defined with a 0.2 MHz gap between them.
Channel zero starts at 433.175 MHz
### 870 MHz
There are eight channels defined with a 0.3 MHz gap between them.
Channel zero starts at 865.20 MHz
## LoRaWAN for North America
LoRaWAN defines 64, 125 kHz channels from 902.3 to 914.9 MHz increments.
The maximum output power for North America is +30 dBM.
The band is from 902 to 928 MHz. It mentions channel number and its respective channel frequency. All the 13 channels are separated by 2.16 MHz with respect to the adjacent channels.
Channel zero starts at 903.08 MHz center frequency.
You probably don't care about this section - skip to the next one.
Threading tasks:
- Use https://github.com/ivanseidel/ArduinoThread? rather than full coroutines
- clean up main loop()
- check that we are mostly asleep, show which thread is causing us to wake
-
- use tickless idle on nrf52, and sleep X msec or until an interrupt occurs or the cooperative scheduling changes. https://devzone.nordicsemi.com/f/nordic-q-a/12363/nrf52-freertos-power-consumption-tickless-idle
- BAD IDEA: use vTaskDelay and https://www.freertos.org/xTaskAbortDelay.html if scheduling changes. (define INCLUDE_xTaskAbortDelay on ESP32 and NRF52 - seems impossible to find?)
- GOOD IDEA: use xSemaphoreTake to take a semaphore using a timeout. Expect semaphore to not be set, but set it to indicate scheduling has changed.
Nimble tasks:
- readerror.txt stress test bug
- started RPA long test, jul 22 6pm
- implement nimble software update api
- update to latest bins, test OTA again (measure times) and then checkin bins
- do alpha release
* update protocol description per cyclomies email thread
* update faq with antennas https://meshtastic.discourse.group/t/range-test-ideas-requested/738/2
* update faq on recommended android version and phones
* add help link inside the app, reference a page on the wiki
* turn on amazon reviews support
* add a tablet layout (with map next to messages) in the android app
# Medium priority
Items to complete before 1.0.
# Post 1.0 ideas
- finish DSR for unicast
- check fcc rules on duty cycle. we might not need to freq hop. https://www.sunfiretesting.com/LoRa-FCC-Certification-Guide/ . Might need to add enforcement for europe though.
- make a no bluetooth configured yet screen - include this screen in the loop if the user hasn't yet paired
- if radio params change fundamentally, discard the nodedb
- re-enable the bluetooth battery level service on the T-BEAM
- provide generalized (but slow) internet message forwarding service if one of our nodes has internet connectivity (MQTT) [ Not a requirement but a personal interest ]
# Low priority ideas
Items after the first final candidate release.
- implement nimble battery level service
- Nimble implement device info service remaining fields (hw version etc)
- Turn on RPA addresses for the device side in Nimble
- Try to teardown less of the Nimble protocol stack across sleep
- dynamic frequency scaling could save a lot of power on ESP32, but it seems to corrupt uart (even with ref_tick set correctly)
- Change back to using a fixed sized MemoryPool rather than MemoryDynamic (see bug #149)
- scan to find channels with low background noise? (Use CAD mode of the RF95 to automatically find low noise channels)
- If the phone doesn't read fromradio mailbox within X seconds, assume the phone is gone and we can stop queing location msgs
for it (because it will redownload the nodedb when it comes back)
- add frequency hopping, dependent on the gps time, make the switch moment far from the time anyone is going to be transmitting
- assign every "channel" a random shared 8 bit sync word (per 4.2.13.6 of datasheet) - use that word to filter packets before even checking CRC. This will ensure our CPU will only wake for packets on our "channel"
- the BLE stack is leaking about 200 bytes each time we go to light sleep
- use fuse bits to store the board type and region. So one load can be used on all boards
- Don't store position packets in the to phone fifo if we are disconnected. The phone will get that info for 'free' when it
fetches the fresh nodedb.
- Use the RFM95 sequencer to stay in idle mode most of the time, then automatically go to receive mode and automatically go from transmit to receive mode. See 4.2.8.2 of manual.
- Use fixed32 for node IDs, packetIDs, successid, failid, and lat/lon - will require all nodes to be updated, but make messages slightly smaller.
- add "store and forward" support for messages, or move to the DB sync model. This would allow messages to be eventually delivered even if nodes are out of contact at the moment.
- use variable length Strings in protobufs (instead of current fixed buffers). This would save lots of RAM
- use BLEDevice::setPower to lower our BLE transmit power - extra range doesn't help us, it costs amps and it increases snoopability
- make a HAM build: just a new frequency list, a bool to say 'never do encryption' and use hte callsign as that node's unique id. -from Girts
- don't forward redundant pings or ping responses to the phone, it just wastes phone battery
- don't send location packets if we haven't moved significantly
- scrub default radio config settings for bandwidth/range/speed
- show radio and gps signal strength as an image
- only BLE advertise for a short time after the screen is on and button pressed - to save power and prevent people for sniffing for our BT app.
- make mesh aware network timing state machine (sync wake windows to gps time) - this can save LOTS of battery
- split out the software update utility so other projects can use it. Have the appload specify the URL for downloads.
- read the PMU battery fault indicators and blink/led/warn user on screen
- discard very old nodedb records (> 1wk)
- handle millis() rollover in GPS.getTime - otherwise we will break after 50 days
- report esp32 device code bugs back to the mothership via android
- change BLE bonding to something more secure. see comment by pSecurity->setAuthenticationMode(ESP_LE_AUTH_BOND)
6. Click the PlatformIO icon on the side bar. 
7. Under `Quick Access, Miscellaneous, Clone Git Project` enter the URL of the Meshtastic repo found [here](https://github.com/meshtastic/Meshtastic-device). 
8. Select a file location to save the repo.
9. Once loaded, open the `platformio.ini` file.
10. At the line `default_envs` you can change it to the board type you are building for ie. `tlora-v2, tlora-v1, tlora-v2-1-1.6, tbeam, heltec, tbeam0.7` (boards are listed further down in the file).
11. The hardware can be configured for different countries by adding a definition to the `configuration.h` file. `#define HW_VERSION_US` or `HW_VERSION_EU433, HW_VERSION_EU865, HW_VERSION_CN, HW_VERSION_JP`. Other country settings can be found in `MeshRadio.h`. The default is `HW_VERSION_US`.
12. Click the PlatformIO icon on the side bar. Under `Project Tasks` you can now build or upload.
Note - To get a clean build you may have to delete the auto-generated file `./.vscode/c_cpp_properties.json`, close and re-open Visual Studio and WAIT until the file is auto-generated before compiling again.
## Command Line
1. Purchase a suitable [radio](https://github.com/meshtastic/Meshtastic-device/wiki/Hardware-Information).
4. Run `git submodule update --init --recursive` to pull in dependencies this project needs.
5. If you are outside the USA, run "export COUNTRY=EU865" (or whatever) to set the correct frequency range for your country. Options are provided for `EU433`, `EU865`, `CN`, `JP` and `US` (default). Pull-requests eagerly accepted for other countries.
6. Plug the radio into your USB port
7. Type `pio run --environment XXX -t upload` (This command will fetch dependencies, build the project and install it on the board via USB). For XXX, use the board type you have (either `tlora-v2, tlora-v1, tlora-v2-1-1.6, tbeam, heltec, tbeam0.7`).
8. Platform IO also installs a very nice VisualStudio Code based IDE, see their [tutorial](https://docs.platformio.org/en/latest/tutorials/espressif32/arduino_debugging_unit_testing.html) if you'd like to use it.
## Decoding stack traces
If you get a crash, you can decode the addresses from the `Backtrace:` line:
1. Save the `Backtrace: 0x....` line to a file, e.g., `backtrace.txt`.
2. Run `bin/exception_decoder.py backtrace.txt` (this uses symbols from the
last `firmware.elf`, so you must be running the same binary that's still in
Cryptography is tricky, so we've tried to 'simply' apply standard crypto solutions to our implementation. However,
the project developers are not cryptography experts. Therefore we ask two things:
- If you are a cryptography expert, please review these notes and our questions below. Can you help us by reviewing our
notes below and offering advice? We will happily give as much or as little credit as you wish ;-).
- Consider our existing solution 'alpha' and probably fairly secure against a not particularly aggressive adversary
(but we can't yet make a more confident statement).
## Summary of strengths/weaknesses of our current implementation
Based on comments from reviewers (see below), here's some tips for usage of these radios. So you can know the level of protection offered:
* It is pretty likely that the AES256 security is implemented 'correctly' and an observer will not be able to decode your messages.
* Warning: If an attacker is able to get one of the radios in their position, they could either a) extract the channel key from that device or b) use that radio to listen to new communications.
* Warning: If an attacker is able to get the "Channel QR code/URL" that you share with others - that attacker could then be able to read any messages sent on the channel (either tomorrow or in the past - if they kept a raw copy of those broadcast packets)
Possible future areas of work (if there is enough interest - post in our [forum](https://meshtastic.discourse.group) if you want this):
1. Optionally requiring users to provide a PIN to regain access to the mesh. This could be based on: intentionally locking the device, time since last use, or any member could force all members to reauthenticate,
2. Until a device reauthenticates, any other access via BLE or USB would be blocked (this would protect against attackers who are not prepared to write custom software to extract and reverse engineer meshtastic flash memory)
3. Turning on read-back protection in the device fuse-bits (this would extend protection in #2 to block all but **extremely** advanced attacks involving chip disassembly)
4. Time limiting keys used for message transmission and automatically cycling them on a schedule. This would protect past messages from being decoded even if an attacker learns the current key.
### Notes for reviewers
If you are reviewing our implementation, this is a brief statement of our method.
- We do all crypto at the SubPacket (payload) level only, so that all meshtastic nodes will route for others - even those channels which are encrypted with a different key.
- Mostly based on reading [Wikipedia](<https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_(CTR)>) and using the modes the ESP32 provides support for in hardware.
- We use AES256-CTR as a stream cypher (with zero padding on the last BLOCK) because it is well supported with hardware acceleration.
- Our AES key is 128 or 256 bits, shared as part of the 'Channel' specification.
- The node number concatenated with the packet number is used as the NONCE. This nonce will be stored in flash in the device and should essentially never repeat. If the user makes a new 'Channel' (i.e. picking a new random 256 bit key), the packet number will start at zero.
- The packet number is sent in cleartext with each packet. The node number can be derived from the "from" field of each packet. (Cleartext is acceptable because it merely provides IV for each encryption run)
- Each 16 byte BLOCK for a packet has an incrementing COUNTER. COUNTER starts at zero for the first block of each packet.
- The IV for each block is constructed by concatenating the NONCE as the upper 96 bits of the IV and the COUNTER as the bottom 32 bits. Since our packets are small counter portion will really never be higher than 32 (five bits).
## Comments from reviewer #1
This reviewer is a cryptography professional, but would like to remain anonymous. We thank them for their comments ;-):
I'm assuming that meshtastic is being used to hike in places where someone capable is trying to break it - like you were going to walk around DefCon using these. I spent about an hour reviewing the encryption, and have the following notes:
* The write-up isn't quite as clear as the code.
* The code is using AES-CTR mode correctly to ensure confidentiality.
* The comment for initNonce really covers the necessary information.
* I think the bigger encryption question is "what does the encryption need to do"? As it stands, an attacker who has yet to capture any of the devices cannot reasonably capture text or location data. An attacker who captures any device in the channel/mesh can read everything going to that device, everything stored on that device, and any other communication within the channel that they captured in encrypted form. If that capability basically matches your expectations, it is suitable for whatever adventures this was intended for, then, based on information publicly available or widely disclosed, the encryption is good. If those properties are distressing (like, device history is deliberately limited and you don't want a device captured today to endanger the information sent over the channel yesterday) we could talk about ways to achieve that (most likely synchronizing time and replacing the key with its own SHA256 every X hours, and ensuring the old key is not retained unnecessarily).
* Two other things to keep in mind are that AES-CTR does not itself provide authenticity (e.g. an attacker can flip bits in replaying data and scramble the resulting plaintext), and that the current scheme gives some hints about transmission in the size. So, if you worry about an adversary deliberately messing-up messages or knowing the length of a text message, it looks like those might be possible.
I'm guessing that the network behaves somewhat like a store-and-forward network - or, at least, that the goal is to avoid establishing a two-way connection to transmit data. I'm afraid I haven't worked with mesh networks much, but remember studying them briefly in school about ten years ago.
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