send/frontend/src/utils.js

function ivToStr(iv) {
  let hexStr = '';
  for (const i in iv) {
    if (iv[i] < 16) {
      hexStr += '0' + iv[i].toString(16);
    } else {
      hexStr += iv[i].toString(16);
    }
  }
  window.hexStr = hexStr;
  return hexStr;
}

function strToIv(str) {
  const iv = new Uint8Array(16);
  for (let i = 0; i < str.length; i += 2) {
    iv[i / 2] = parseInt(str.charAt(i) + str.charAt(i + 1), 16);
  }

  return iv;
}

module.exports = {
  ivToStr,
  strToIv
};