funglaub

var crypto = require('crypto')
  , key = 'salt_from_the_user_document'
  , plaintext = 'password'
  , cipher = crypto.createCipher('aes-256-cbc', key)
  , decipher = crypto.createDecipher('aes-256-cbc', key);
  
cipher.update(plaintext, 'utf8', 'base64');
var encryptedPassword = cipher.final('base64')

decipher.update(encryptedPassword, 'base64', 'utf8');

funglaub

// make sure we're using the right db; this is the same as "use aggdb;" in shell
db = db.getSiblingDB("aggdb");

// simple projection
var p1 = db.runCommand(
{ aggregate : "article", pipeline : [
    { $project : {
	tags : 1,
	pageViews : 1
    }}