LoRaWAN-Signal-Mapping/server/ttn-app-server/DecodePayload.mjs

"use strict";

import aes from 'aes-js';

const offset_id = 0;
const offset_lat = 32 / 8;
const offset_lng = (32 / 8) + (32 / 8);

function decode_payload(payload_base64, key_hex) {
	let payload_buffer_enc = Buffer.from(payload_base64, "base64");
	let key_buffer = Buffer.from(key_hex, "hex");
	
	// console.log(payload_buffer_enc);
	
	let aes_ecb = new aes.ModeOfOperation.ecb(key_buffer);
	let payload_buffer = Buffer.from(aes_ecb.decrypt(payload_buffer_enc).buffer);
	
	// console.debug(payload_buffer);
	// console.debug(`Offsets: ${offset_id}, ${offset_lat}, ${offset_lng}`);
	// console.debug(`Message hex: ${payload_buffer.toString("hex")}`)
	
	return {
		id: payload_buffer.readUInt32LE(offset_id),
		latitude: payload_buffer.readFloatLE(offset_lat),
		longitude: payload_buffer.readFloatLE(offset_lng)
	};
}

export { decode_payload };