// randomSeedEntropyInjection
// https://wokwi.com/projects/428238528418621441

const int injectPin = 2;

void setup() {
  pinMode(injectPin, INPUT_PULLUP);
  Serial.begin(115200);
  Serial.println(F(R"(This sketch injects user-based entropy from
serial input into the Arduino RNG by using 
randomSeed(random() + micros()) when the switch is closed.
Without injection, random() starts with 16807,282475249,1622650073,... 
With injection, it will advance to somwhere else in the 2^31-1 cycle of numbers.)"));

  Serial.println("Hit Enter to begin...");
  while (Serial.available() == 0 ) {} // wait for input
  if (digitalRead(injectPin) == LOW) {
    randomSeed(random() + micros()); //inject some user-based randomness
  }
}

void loop() {
  if (Serial.available()) {
    Serial.println(random());
    Serial.readStringUntil('\n'); // consume line
    if (digitalRead(injectPin) == LOW) {
      //inject more user-input-based randomness
      randomSeed(random() + micros());
      //randomSeed(0);
      //randomSeed(1);
      //randomSeed(16807);
    }
  };
}