my-idlers/node_modules/browserify-aes/modes/cbc.js

var xor = require('buffer-xor')

exports.encrypt = function (self, block) {
  var data = xor(block, self._prev)

  self._prev = self._cipher.encryptBlock(data)
  return self._prev
}

exports.decrypt = function (self, block) {
  var pad = self._prev

  self._prev = block
  var out = self._cipher.decryptBlock(block)

  return xor(out, pad)
}