erlang-bcrypt is a wrapper around the OpenBSD Blowfish password hashing algorithm, as described in "A Future-Adaptable Password Scheme" by Niels Provos and David Mazieres.

1. Build it (project uses rebar, but I've included a Makefile):

   make
   

2. Run it (simple way, starting sasl, crypto and bcrypt):

   erl -pa ebin -boot start_sasl -s crypto -s bcrypt
   

3. Hash a password using a salt with the default number of rounds:

   1> {ok, Salt} = bcrypt:gen_salt(),
   {ok,"$2a$12$sSS8Eg.ovVzaHzi1nUHYK."}
   2> {ok, Hash} = bcrypt:hashpw("foo", Salt),
   {ok,"$2a$12$sSS8Eg.ovVzaHzi1nUHYK.HbUIOdlQI0iS22Q5rd5z.JVVYH6sfm6"}
   

3. Verify the password:

   3> {ok, Hash} =:= bcrypt:hashpw("foo", Hash).
   true
   4> {ok, Hash} =:= bcrypt:hashpw("bar", Hash).
   false
   

The bcrypt application is configured by changing values in the application's environment:

default_log_rounds

Sets the default number of rounds which define the complexity of the hash function. Defaults to 12.

mechanism

Specifies whether to use the NIF implementation ('nif') or a pool of port programs ('port'). Defaults to 'nif'.

Note: the NIF implementation no longer blocks the Erlang VM scheduler threads

pool_size

Specifies the size of the port program pool. Defaults to 4.

• Hunter Morris
• Mrinal Wadhwa