bcrypt

A comparison of JavaScript / Node.js bcrypt implementations.

Why use bcrypt?

The main aim of bcrypt is to be computationally slow for an attacker to crack the passwords if (when) your password database is stolen!

bcrypt is an adaptive function: over time, the iteration count can be increased to make it slower, so it remains resistant to brute-force search attacks even with increasing computation power.

The cost factor for bcrypt is exponential, or rather, a cost factor of 10 means 2^10 rounds (1024), a cost factor of 16 would mean 2^16 rounds (65536). It's natural then that it would take 5-10 seconds. It should take about 64 times as long as a cost factor of 10 does.

A detailed overview of why you should use bcrypt can be found here:

• How To Safely Store A Password: http://codahale.com/how-to-safely-store-a-password/
• Use BCrypt Fool! http://yorickpeterse.com/articles/use-bcrypt-fool/
• Use Bcrypt. Always. https://news.ycombinator.com/item?id=2004962

If you are unconvinced or paranoid that bcrypt has been cracked by the "bad guys", please do your own research and send us your findings!

The purpose of this post is to compare the available node.js bcrypt modules.

Which bcrypt node.js module?

As with most things npm there are several to chose from.

npm

We are going to compare the 4 most popular modules:

• bcrypt: https://www.npmjs.com/package/bcrypt > https://github.com/ncb000gt/node.bcrypt.js/
• bcryptjs: https://www.npmjs.com/package/bcryptjs > https://github.com/dcodeIO/bcrypt.js
• bcrypt-nodejs: https://www.npmjs.com/package/bcrypt-nodejs > https://github.com/shaneGirish/bcrypt-nodejs
• twin-bcrypt: https://www.npmjs.com/package/twin-bcrypt > https://github.com/fpirsch/twin-bcrypt (twin-bcrypt has a much simpler hash and compair method)

FAQ

• Q: The hash is never the same, how do I know its working?
  A: That got me too at first. But you need to remember that the under the hood its generating a dynamic salt so it will never appear the same.

Try it yourself:

var bcrypt  = require('bcrypt');
var howmany = 10;
var cost    = 12;

for(var i = 1; i <= howmany; i++){
  bcrypt.genSalt(12, function(err, salt) {
    bcrypt.hash("hello", salt, function(err, hash) {
      console.log(hash);
    });
  });
}

Output (10 bcrypt hashes) all for the password "hello":

$2a$12$OgPE9DUNM0KaSodSQVJvw.36GjolssAeO.dfi7a9cmc9KbQTDTj7W
$2a$12$BbJMnIitZhp3tFiwP/XkkeCktZg6dLL/6IaB2rJyHYod/LnroCy1K
$2a$12$9wEav5ce7FDKT3rL7vPLNeLeU6kFtFR/zNRZAxzoxpjroC.S/8FFa
$2a$12$uBCwQKkMJLsy.QA/PXJ3QeLF/yh3v0kFyg1hY9JXEam0SCYWpwrWi
$2a$12$25Xn/4uoeat7l2kTJlnnEu/6ezQ0o6r2Upm9bmFdFiKmvCW6BR5sO
$2a$12$sIAs7K5JuJihDBnR1lfUCOQ.1dvyd5vwQQtFH3RVz/y0c3LtWWHKq
$2a$12$cb9NqlIZvcNdwUbSUfLsC.8u/epdnUdqSFeohO825dCJEDgG6ah6y
$2a$12$NH6DShsNj7tPNXf8r0XXbOYvaJFfEBSCMjpxRfhnK1XOnltfAR6Ia
$2a$12$jhiSa8FFwKkAJbvtZpSMjusDQNXhkdCkE.x1uSBFvwS52AL.7.0d.
$2a$12$sEhB/EyvhfCa0QMsBCUj9.Li69xFYZ8EcWdto4N2zke3q3X/BpCSG

But when you use the compareSync method, it will calculate the check using the salt in the original hash.

The modular crypt format for bcrypt consists of

• $2$, $2a$ or $2y$ identifying the hashing algorithm and format,
• a two digit value denoting the cost parameter, followed by $
• a 53 characters long base-64-encoded value (they use the alphabet ., /, 0–9, A–Z, a–z that is different to the standard Base 64 Encoding alphabet) consisting of:
  • 22 characters of salt (effectively only 128 bits of the 132 decoded bits)
  • 31 characters of encrypted output (effectively only 184 bits of the 186 decoded bits)

Thus the total length is 59 or 60 bytes respectively.

See: Explanation of the bcrypt format: http://stackoverflow.com/a/5882472/1148249