哪位大神解答一下，微信小程序后端如何解密openid、phoneNumber

本人服务器端用的是Nodejs，哪位大神能指点一下如何用这下面两个官方文档在服务器解密openid以及phoneNumber
这是微信官网的解密文档：
1.WXBizDataCrypt.js:

var crypto = require('crypto')

function WXBizDataCrypt(appId, sessionKey) {
  this.appId = appId
  this.sessionKey = sessionKey
}

WXBizDataCrypt.prototype.decryptData = function (encryptedData, iv) {
  // base64 decode
  var sessionKey = new Buffer(this.sessionKey, 'base64')
  encryptedData = new Buffer(encryptedData, 'base64')
  iv = new Buffer(iv, 'base64')

  try {
     // 解密
    var decipher = crypto.createDecipheriv('aes-128-cbc', sessionKey, iv)
    // 设置自动 padding 为 true，删除填充补位
    decipher.setAutoPadding(true)
    var decoded = decipher.update(encryptedData, 'binary', 'utf8')
    decoded += decipher.final('utf8')

    decoded = JSON.parse(decoded)

  } catch (err) {
    throw new Error('Illegal Buffer')
  }

  if (decoded.watermark.appid !== this.appId) {
    throw new Error('Illegal Buffer')
  }

  return decoded
}

module.exports = WXBizDataCrypt

2.demo.js:

var WXBizDataCrypt = require('./WXBizDataCrypt')

var appId = 'wx4f4bc4dec97d474b'
var sessionKey = 'tiihtNczf5v6AKRyjwEUhQ=='
var encryptedData = 
    'CiyLU1Aw2KjvrjMdj8YKliAjtP4gsMZM'+
    'QmRzooG2xrDcvSnxIMXFufNstNGTyaGS'+
    '9uT5geRa0W4oTOb1WT7fJlAC+oNPdbB+'+
    '3hVbJSRgv+4lGOETKUQz6OYStslQ142d'+
    'NCuabNPGBzlooOmB231qMM85d2/fV6Ch'+
    'evvXvQP8Hkue1poOFtnEtpyxVLW1zAo6'+
    '/1Xx1COxFvrc2d7UL/lmHInNlxuacJXw'+
    'u0fjpXfz/YqYzBIBzD6WUfTIF9GRHpOn'+
    '/Hz7saL8xz+W//FRAUid1OksQaQx4CMs'+
    '8LOddcQhULW4ucetDf96JcR3g0gfRK4P'+
    'C7E/r7Z6xNrXd2UIeorGj5Ef7b1pJAYB'+
    '6Y5anaHqZ9J6nKEBvB4DnNLIVWSgARns'+
    '/8wR2SiRS7MNACwTyrGvt9ts8p12PKFd'+
    'lqYTopNHR1Vf7XjfhQlVsAJdNiKdYmYV'+
    'oKlaRv85IfVunYzO0IKXsyl7JCUjCpoG'+
    '20f0a04COwfneQAGGwd5oa+T8yO5hzuy'+
    'Db/XcxxmK01EpqOyuxINew=='
var iv = 'r7BXXKkLb8qrSNn05n0qiA=='

var pc = new WXBizDataCrypt(appId, sessionKey)

var data = pc.decryptData(encryptedData , iv)

console.log('解密后 data: ', data)