Using Crypt::Argon2 is probably a better alternative to Bcrypt password hashing.

After APR1 password verification came Bcrypt password hashing. But, of course, I had to look if there’s anything newer, and sure there is.

It’s like opening the proverbial can of worms, except that this time the can contains a lot of good food.

It all starts from the Password Hashing Competition and its winner, the Argon2 password:

We recommend that you use Argon2 rather than legacy algorithms.

Next step is to make a bet… is there a module for this in CPAN?

Sure there is: Crypt::Argon2. There are a few alternative functions to choose from, but sticking with the id variants provides us this:

#!/usr/bin/env perl
use 5.024;
use warnings;
use experimental qw< postderef signatures >;
no warnings qw< experimental::postderef experimental::signatures >;

use FindBin '$Bin';
use lib "$Bin/local/lib/perl5";

use Crypt::Argon2 qw< argon2id_pass argon2id_verify >;
use Crypt::URandom 'urandom';
use Test::More;

   my %db;
   sub save_user ($u, $p) { $db{$u} = $p }
   sub get_user_hashed_password ($u) { return $db{$u} // undef }

sub salt_please { return urandom(16) }

sub create_account ($username, $password, $cost, $salt = undef) {
   $salt //= salt_please();
   my $encoded = argon2id_pass($password, $salt, $cost, '32M', 1, 16);
   save_user($username, $encoded);

sub authenticate ($username, $password) {
   my $expected = get_user_hashed_password($username) // return;
   return argon2id_verify($expected, $password);

create_account(foo => 'barbaz', $ENV{BCRYPT_COST} // 9);

my $hp = get_user_hashed_password('foo');
like $hp, qr{\A\$argon2id\$}mxs, 'hashed password saved as expected';

ok ! authenticate(foo => $_), 'attempt wrong password'
   for qw< bar baz bar-baz >;
ok   authenticate(foo => 'barbaz'), 'authenticate with right pass';


If you’re wondering… yes, this is mostly copied from Bcrypt password hashing, and for good reasons: it reuses that scaffolding and fills in a different implementation for the same interface, in good spirit of encapsulation.

This is so interesting!