code: async function getPkcs1Padding(length) {
    let result = '';
    while (result.length < length) {
      const randomBytes = await random.getRandomBytes(length - result.length);
      for (let i = 0; i < randomBytes.length; i++) {
        if (randomBytes[i] !== 0) {
          result += String.fromCharCode(randomBytes[i]);
        }
      }
    }
    return result;
  }
docs: Create padding with secure random data
  @private
  @param  {Integer} length Length of the padding in bytes
  @returns {String}        Padding as string
  @async