README.md

BastWAN_DHKE

A project demonstrating how to do Diffie Hellman Key Exchange on the BastWAN/RAK4260.

It relies on 3 libraries, which are included in the code:

• aes.c/h an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
• DHKE.h my implementation of Diffie-Hellman Key Exchange, using (for now) AES ECB.
• LoRandom.h my implementation of LoRa-based RNG. It is library independent. To use the LoRandom.h library in your code, you need to provide 2 functions:

  void writeRegister(uint8_t reg, uint8_t value);
  uint8_t readRegister(uint8_t reg);

You need to call void setupLoRandom() at startup, and uint8_t getLoRandomByte() when you need a random byte. This code creates a stock of 256 bytes at startup to make things easier. Remember you need to reset LoRa settings when you need RNG...

Update 2020/08/31

This version adds CTR encryption/decryption to the mix. You can now choose between ECB, CBC and CTR, and the code handles the IV from the randomStock array.

The filling up of the randomStock array has been moved to a function inside LoRandom.h, and made parametrable.

void fillRandom(unsigned char *x, size_t len) {
  size_t i;
  for (i = 0; i < len; i++) {
    x[i] = getLoRandomByte();
  }
}

There was a bug in buddy::decrypt() where the destination array wasn't updated. Oopsies.

Update 2020/08/30

This version adds CBC encryption to the mix. You can now choose between ECB and CBC, and the code handles the IV from the randomStock array.