app.txt

authenticate_message(message) {
  secret_key = get_secret_key(message.public_key)
  my_signature = sprintf("payload=%s&public_key=%s&timestamp=%s&type=%s",
                 url_encode(message.payload),
                 url_encode(message.public_key),
                 url_encode(message.timestamp),
                 url_encode(message.type))
  
  return hmac_sha256(my_signature, secret_key) == message.signature
}

on_message_received(message) {
  if(authenticate_message(message)) {
    Do something sensative, like saving the data.
  }
  else {
    The message has an invalid signature! Throw it away.
  }
}