v0.1.0-alpha.3

The third alpha, for Heltec WiFi LoRa 32 V3 boards. Two boards no longer have to hear each other
to meet: first contact goes through relays, as messages already did.

It is an alpha. The protocol is a draft and will change, and a later build may not talk to this
one or keep its sessions. Nobody outside the project has reviewed the cryptography. Do not rely
on it for anything that matters.

What changed

• First contact follows routes. The four frames of the handshake are passed on by relays, hop
  by hop, so a board can make a session with any board it has a route to. Until now the two had
  to be in range of each other to meet, and only then could their messages go through a mesh.
• A lost handshake frame is sent again as a lost message is. The board that began waits five
  seconds and a little for each answer, tries up to four times, and then says it gave up. The
  other board answers again when asked and never sends unasked.
• A board that starts a handshake again is answered at once. It used to wait out the one it
  had left.
• A handshake's frames now name both boards' routing ids, as a message and its acknowledgement
  do between them. Neither address is on the air.

This was run on two boards in range of each other, and through a relay only in tests on a
computer: the project has two boards. If you have three and can put the middle one between two
that do not hear each other, that is the report we most want.

Updating

Update every board together. The handshake's frames changed, so a board on this build and
one on 0.1.0-alpha.2 cannot make first contact with each other. Sessions they already have keep
working, and messages still pass between them.

A board running an earlier alpha keeps its address, sessions and contacts if you write the
-app.bin image at 0x10000; https://ternmesh.org/flash does that when you say the board runs
Tern already.

tern-heltec-v3-us915-0.1.0-alpha.3.bin	United States, Canada: 921.25 MHz
tern-heltec-v3-eu868-0.1.0-alpha.3.bin	Europe: 869.475 MHz, at most 10% of any hour

The full images are written at 0x0, replace whatever is on the board, and give it a new
address. Never power a board with nothing on the antenna connector. SHA256SUMS has the
SHA-256 of each image.

What is still not in it

• No group or broadcast messages. Every message is to one address.
• Messages are kept only in memory on the board. The web client keeps what it has seen in
  the browser; a message that arrives while no client is connected is lost if the board restarts
  before one connects.
• The web client does not use Bluetooth yet, so there is no phone client.
• Boards start at 2 dBm, a bench setting that reaches across a building, not a town, until
  you raise it.
• Keys sit in flash unencrypted. Anyone holding the board can read them.
• One board only. An nRF52 port is next.