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https://github.com/bcrypt-ruby/bcrypt-ruby

bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm, allowing you to easily store a secure hash of your users' passwords.
https://github.com/bcrypt-ruby/bcrypt-ruby

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bcrypt-ruby is a Ruby binding for the OpenBSD bcrypt() password hashing algorithm, allowing you to easily store a secure hash of your users' passwords.

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# bcrypt-ruby



An easy way to keep your users' passwords secure.



* https://github.com/bcrypt-ruby/bcrypt-ruby/tree/master



[![Github Actions Build Status](https://github.com/bcrypt-ruby/bcrypt-ruby/actions/workflows/ruby.yml/badge.svg?branch=master)](https://github.com/bcrypt-ruby/bcrypt-ruby/actions/workflows/ruby.yml)



## Why you should use `bcrypt()`



If you store user passwords in the clear, then an attacker who steals a copy of your database has a giant list of emails

and passwords. Some of your users will only have one password -- for their email account, for their banking account, for

your application. A simple hack could escalate into massive identity theft.



It's your responsibility as a web developer to make your web application secure -- blaming your users for not being

security experts is not a professional response to risk.



`bcrypt()` allows you to easily harden your application against these kinds of attacks.



*Note*: JRuby versions of the bcrypt gem `<= 2.1.3` had a [security

vulnerability](https://www.mindrot.org/files/jBCrypt/internat.adv) that

was fixed in `>= 2.1.4`. If you used a vulnerable version to hash

passwords with international characters in them, you will need to

re-hash those passwords. This vulnerability only affected the JRuby gem.



## How to install bcrypt



    gem install bcrypt



The bcrypt gem is available on the following Ruby platforms:



* JRuby

* RubyInstaller builds on Windows with the DevKit

* Any modern Ruby on a BSD/OS X/Linux system with a compiler



## How to use `bcrypt()` in your Rails application



*Note*: Rails versions >= 3 ship with `ActiveModel::SecurePassword` which uses bcrypt-ruby.

`has_secure_password` [docs](https://api.rubyonrails.org/classes/ActiveModel/SecurePassword/ClassMethods.html#method-i-has_secure_password)

implements a similar authentication strategy to the code below.



### The _User_ model

```ruby

require 'bcrypt'



class User < ActiveRecord::Base

  # users.password_hash in the database is a :string

  include BCrypt



  def password

    @password ||= Password.new(password_hash)

  end



  def password=(new_password)

    @password = Password.create(new_password)

    self.password_hash = @password

  end

end

```

### Creating an account

```ruby

def create

  @user = User.new(params[:user])

  @user.password = params[:password]

  @user.save!

end

```

### Authenticating a user

```ruby

def login

  @user = User.find_by_email(params[:email])

  if @user.password == params[:password]

    give_token

  else

    redirect_to home_url

  end

end

```

## How to use bcrypt-ruby in general

```ruby

require 'bcrypt'



my_password = BCrypt::Password.create("my password")

#=> "$2a$12$K0ByB.6YI2/OYrB4fQOYLe6Tv0datUVf6VZ/2Jzwm879BW5K1cHey"



my_password.version              #=> "2a"

my_password.cost                 #=> 12

my_password == "my password"     #=> true

my_password == "not my password" #=> false



my_password = BCrypt::Password.new("$2a$12$K0ByB.6YI2/OYrB4fQOYLe6Tv0datUVf6VZ/2Jzwm879BW5K1cHey")

my_password == "my password"     #=> true

my_password == "not my password" #=> false

```

Check the rdocs for more details -- BCrypt, BCrypt::Password.



## How `bcrypt()` works



`bcrypt()` is a hashing algorithm designed by Niels Provos and David Mazières of the OpenBSD Project.



### Background



Hash algorithms take a chunk of data (e.g., your 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) #=> 



You can store the hash and check it against a hash made of a potentially valid password:



     =? hash(just_entered_password)



### Rainbow Tables



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().password #=> "secret1"



### Salts



The 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) #=> 



The salt is then stored along with the hash in the database, and used to check potentially valid passwords:



     =? 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") =? 

    hash(salt + "abacus")  =? 

    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()`.



### Cost Factors



In addition, `bcrypt()` allows you to increase the amount of work required to hash a password as computers get faster. Old

passwords will still work fine, but new passwords can keep up with the times.



The default cost factor used by bcrypt-ruby is 12, which is fine for session-based authentication. If you are using a

stateless authentication architecture (e.g., HTTP Basic Auth), you will want to lower the cost factor to reduce your

server load and keep your request times down. This will lower the security provided you, but there are few alternatives.



To change the default cost factor used by bcrypt-ruby, use `BCrypt::Engine.cost = new_value`:

```ruby

BCrypt::Password.create('secret').cost

  #=> 12, the default provided by bcrypt-ruby



# set a new default cost

BCrypt::Engine.cost = 8

BCrypt::Password.create('secret').cost

  #=> 8

```

The default cost can be overridden as needed by passing an options hash with a different cost:



    BCrypt::Password.create('secret', :cost => 6).cost  #=> 6



## More Information



`bcrypt()` is currently used as the default password storage hash in OpenBSD, widely regarded as the most secure operating

system available.



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



# Etc



* Author  :: Coda Hale 

* Website :: https://codahale.com