crypto test: AES CCM BTHome advertisement

crypto_AES_CCM_bthome.js

// crypto test for aes ccm, for (eventual) bthome encryption
// see: https://bthome.io/encryption

let macAddress = "5448E68F80A5";
let uuid = "d2fc";
let btHomeDeviceDataByte = "41"
let counter = "00112233";
let key = "231d39c1d7cc1ab1aee224cd096db932";
let data = "02CA0903BF13";

let nonce = macAddress + uuid + btHomeDeviceDataByte + counter;
print("nonce: " + nonce);

function hexStringToArrayBuffer(str) {
  if (str.length % 2 != 0) {
    return null;
  }
  let length = str.length / 2;
  let buf = Uint8Array(length);
  for (let i=0; i<length; i++) {
    buf[i] = parseInt(str.slice(i * 2, i * 2 + 2), 16);
  }
  return buf;
}

function arrayBufferToHexString(buf) {
  let str = "";
  for (let i=0; i<buf.length; i++) {
    str += buf[i].toString(16).padStart(2, '0');
  }
  return str;
}


let keyBuf = hexStringToArrayBuffer(key);
let iv = hexStringToArrayBuffer(nonce);
let dataBuf = hexStringToArrayBuffer(data);
let result = AES.ccmEncrypt(dataBuf, keyBuf, iv, 4);
let resultString = arrayBufferToHexString(result.data);
print("encrypted data: " + resultString);
let resultTagString = arrayBufferToHexString(result.tag);
print("tag: " + resultTagString);

let decryptResult = AES.ccmDecrypt(result.data, keyBuf, iv, result.tag);
let decryptResultString = arrayBufferToHexString(decryptResult);
print("decrypted: " + decryptResultString);

if (data.toLowerCase() == decryptResultString) {
  print("success: unencrypted and decrypted data match!");
} else {
  print("error: unencrypted and decrypted data don't match!");
}