Barong since 2.0 version use OpenBSD bcrypt() password hashing algorithm, that allow us easily store a secure hash of users' passwords.
Hash algorithms take a chunk of data (e.g., user's password) and create a "digital fingerprint," or hash, of it. Because this process is not reversible, there's no way to go from the hash back to the password.
In other words:
hash(p) #=> <unique gibberish>
We store the hash and check it against a hash made of a potentially valid password:
<unique gibberish> =? hash(just_entered_password)
But even this has weaknesses -- attackers can just run lists of possible passwords through the same algorithm, store the results in a big database, and then look up the passwords by their hash:
PrecomputedPassword.find_by_hash(<unique gibberish>).password #=> "secret1"
Our solution to this is to add a small chunk of random data -- called a salt -- to the password before it's hashed:
hash(salt + p) #=> <really unique gibberish>
The salt is then stored along with the hash in the database, and used to check potentially valid passwords:
<really unique gibberish> =? hash(salt + just_entered_password)
bcrypt-ruby automatically handles the storage and generation of these salts for you.
Adding a salt means that an attacker has to have a gigantic database for each unique salt -- for a salt made of 4 letters, that's 456,976 different databases. Pretty much no one has that much storage space, so attackers try a different, slower method -- throw a list of potential passwords at each individual password:
hash(salt + "aadvark") =? <really unique gibberish> hash(salt + "abacus") =? <really unique gibberish> etc.
This is much slower than the big database approach, but most hash algorithms are pretty quick -- and therein lies the
problem. Hash algorithms aren't usually designed to be slow, they're designed to turn gigabytes of data into secure
fingerprints as quickly as possible.
bcrypt(), though, is designed to be computationally expensive:
Ten thousand iterations: user system total real md5 0.070000 0.000000 0.070000 ( 0.070415) bcrypt 22.230000 0.080000 22.310000 ( 22.493822)
If an attacker was using Ruby to check each password, they could check ~140,000 passwords a second with MD5 but only
~450 passwords a second with
bcrypt() is currently used as the default password storage hash in OpenBSD, widely regarded as the most secure operating
For a more technical explanation of the algorithm and its design criteria, please read Niels Provos and David Mazières' Usenix99 paper: https://www.usenix.org/events/usenix99/provos.html
If you'd like more down-to-earth advice regarding cryptography, I suggest reading Practical Cryptography by Niels Ferguson and Bruce Schneier: https://www.schneier.com/book-practical.html