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Crypt::Eksblowfish::Bcrypt - Blowfish-based Unix crypt() password hash


        use Crypt::Eksblowfish::Bcrypt qw(bcrypt_hash);

        $hash = bcrypt_hash({
                        key_nul => 1,
                        cost => 8,
                        salt => $salt,
                }, $password);

        use Crypt::Eksblowfish::Bcrypt qw(en_base64 de_base64);

        $text = en_base64($octets);
        $octets = de_base64($text);

        use Crypt::Eksblowfish::Bcrypt qw(bcrypt);

        $hashed_password = bcrypt($password, $settings);


This module implements the Blowfish-based Unix crypt() password hashing algorithm, known as "bcrypt". This hash uses a variant of Blowfish, known as "Eksblowfish", modified to have particularly expensive key scheduling. Eksblowfish and bcrypt were devised by Niels Provos and David Mazieres for OpenBSD. The design is described in a paper at



Hashes PASSWORD according to the supplied SETTINGS, and returns the 23-octet hash. SETTINGS must be a reference to a hash, with these keys:


Truth value: whether to append a NUL to the password before using it as a key. The algorithm as originally devised does not do this, but it was later modified to do it. The version that does append NUL is to be preferred; not doing so is supported only for backward compatibility.


Non-negative integer controlling the cost of the hash function. The number of operations is proportional to 2^cost.


Exactly sixteen octets of salt.


Encodes the octet string textually using the form of base 64 that is conventionally used with bcrypt.


Decodes an octet string that was textually encoded using the form of base 64 that is conventionally used with bcrypt.


This is a version of crypt (see "crypt" in perlfunc) that implements the bcrypt algorithm. It does not implement any other hashing algorithms, so if others are desired then it necessary to examine the algorithm prefix in SETTINGS and dispatch between more than one version of crypt.

SETTINGS must be a string which encodes the algorithm parameters, including salt. It must begin with "$2", optional "a", "$", two digits, "$", and 22 base 64 digits. The rest of the string is ignored. The presence of the optional "a" means that a NUL is to be appended to the password before it is used as a key. The two digits set the cost parameter. The 22 base 64 digits encode the salt. The function will die if SETTINGS does not have this format.

The PASSWORD is hashed according to the SETTINGS. The value returned is a string which encodes the algorithm parameters and the hash: the parameters are in the same format required in SETTINGS, and the hash is appended in the form of 31 base 64 digits. This result is suitable to be used as a SETTINGS string for input to this function: the hash part of the string is ignored on input.




Andrew Main (Zefram) <>


Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Andrew Main (Zefram) <>


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