Crypt::Bcrypt - A modern bcrypt implementation


version 0.007


 use Crypt::Bcrypt qw/bcrypt bcrypt_check/;

 my $hash = bcrypt($password, '2b', 12, $salt);

 if (bcrypt_check($password, $hash)) {


This module provides a modern and user-friendly implementation of the bcrypt password hash.

Note that in bcrypt passwords may only contain 72 characters. It may seem tempting to prehash the password before bcrypting it but that may make it vulnerable to password shucking, a salted solution (for example using a MAC) should be used instead if one wants to support large passwords.

The password is always expected to come as a (utf8-encoded) byte-string.


bcrypt($password, $subtype, $cost, $salt)

This computes the bcrypt hash for $password in $subtype, with $cost and $salt.

Valid subtypes are:

  • 2b

    This is the subtype the rest of the world has been using since 2014, you should use this unless you have a very specific reason to use something else.

  • 2a

    This is an old and subtly buggy version of bcrypt. This is mainly useful for Crypt::Eksblowfish compatibility.

  • 2y

    This type is considered equivalent to 2b, and is only commonly used on php.

  • 2x

    This is a very broken version that is only useful for compatibility with ancient php versions.

$cost must be between 5 and 31 (inclusive). $salt must be exactly 16 bytes.

bcrypt_check($password, $hash)

This checks if the $password satisfies the $hash, and does so in a timing-safe manner.


  • Crypt::Passphrase

    This is usually a better approach to managing your passwords, it can use this module via Crypt::Passphrase::Bcrypt. It adds support for automatic pre-hashing, and facilitates upgrading the algorithm parameters or even the algorithm itself.

  • Crypt::Eksblowfish::Bcrypt

    This also offers bcrypt, but only supports the 2a subtype.


Leon Timmermans <>


This software is copyright (c) 2021 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.