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.\" ========================================================================
.\"
.IX Title "Authen::Passphrase::BlowfishCrypt 3pm"
.TH Authen::Passphrase::BlowfishCrypt 3pm "2022-06-08" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Authen::Passphrase::BlowfishCrypt \- passphrases using the Blowfish\-based
Unix crypt()
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&        use Authen::Passphrase::BlowfishCrypt;
\&
\&        $ppr = Authen::Passphrase::BlowfishCrypt\->new(
\&                cost => 8,
\&                salt => "sodium_\|_chloride",
\&                hash_base64 => "BPZijhMHLvPeNMHd6XwZyNamOXVBTPi");
\&
\&        $ppr = Authen::Passphrase::BlowfishCrypt\->new(
\&                cost => 8, salt_random => 1,
\&                passphrase => "passphrase");
\&
\&        $ppr = Authen::Passphrase::BlowfishCrypt\->from_crypt(
\&                \*(Aq$2a$08$a07iYVTrVz7hYEvtakjiXOB\*(Aq.
\&                \*(AqPZijhMHLvPeNMHd6XwZyNamOXVBTPi\*(Aq);
\&
\&        $ppr = Authen::Passphrase::BlowfishCrypt\->from_rfc2307(
\&                \*(Aq{CRYPT}$2a$08$a07iYVTrVz7hYEvtakjiXOB\*(Aq.
\&                \*(AqPZijhMHLvPeNMHd6XwZyNamOXVBTPi\*(Aq);
\&
\&        $key_nul = $ppr\->key_nul;
\&        $cost = $ppr\->cost;
\&        $cost = $ppr\->keying_nrounds_log2;
\&        $salt = $ppr\->salt;
\&        $salt_base64 = $ppr\->salt_base64;
\&        $hash = $ppr\->hash;
\&        $hash_base64 = $ppr\->hash_base64;
\&
\&        if($ppr\->match($passphrase)) { ...
\&
\&        $passwd = $ppr\->as_crypt;
\&        $userPassword = $ppr\->as_rfc2307;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
An object of this class encapsulates a passphrase hashed using the
Blowfish-based Unix \fBcrypt()\fR hash function, known as \*(L"bcrypt\*(R".  This is
a subclass of Authen::Passphrase, and this document assumes that the
reader is familiar with the documentation for that class.
.PP
The \fBcrypt()\fR function in a modern Unix actually supports several different
passphrase schemes.  This class is concerned only with one particular
scheme, a Blowfish-based algorithm designed by Niels Provos and David
Mazieres for OpenBSD.  To handle the whole range of passphrase schemes
supported by the modern \fBcrypt()\fR, see the
from_crypt constructor and the
as_crypt method in Authen::Passphrase.
.PP
The Blowfish-based \fBcrypt()\fR scheme uses a variant of Blowfish called
\&\*(L"Eksblowfish\*(R", for \*(L"expensive key schedule Blowfish\*(R".  It has the
cryptographic strength of Blowfish, and a very slow key setup phase
to resist brute-force attacks.  There is a \*(L"cost\*(R" parameter to the
scheme: the length of key setup is proportional to 2^cost.  There is
a 128\-bit salt.  Up to 72 characters of the passphrase will be used;
any more will be ignored.
.PP
The cost, salt, and passphrase are all used to (very
slowly) key Eksblowfish.  Once key setup is done, the string
\&\*(L"OrpheanBeholderScryDoubt\*(R" (three Blowfish blocks long) is encrypted 64
times in \s-1ECB\s0 mode.  The final byte of the ciphertext is then dropped,
yielding a 23\-byte hash.
.PP
In the \fBcrypt()\fR function the salt and hash are represented in \s-1ASCII\s0
using a base 64 encoding.  The base 64 digits are "\fB.\fR\*(L", \*(R"\fB/\fR\*(L",
\&\*(R"\fBA\fR\*(L" to \*(R"\fBZ\fR\*(L", \*(R"\fBa\fR\*(L" to \*(R"\fBz\fR\*(L", \*(R"\fB0\fR\*(L" to \*(R"\fB9\fR" (in that order).
The 16\-byte salt is represented as 22 base 64 digits, and the 23\-byte
hash as 31 base 64 digits.
.PP
This algorithm is intended for situations where the efficiency of
a brute force attack is a concern.  It is suitable for use in new
applications where this requirement exists.  If that is not a concern,
and it suffices to merely make brute force the most efficient attack, see
Authen::Passphrase::SaltedDigest for more efficient hash algorithms.
.PP
Choice of the cost parameter is critical, due to the need to trade off
expense of brute-force attack against speed of legitimate passphrase
verification.  A traditional target is that verification should take
about one second on widely-available hardware.  (Algorithms that are
concerned about brute force speed but lack a cost parameter have often
aimed for this, with respect to hardware available at the time of the
algorithm's introduction.)  As of 2011, this is achieved with a cost
parameter around 14.
.SH "CONSTRUCTORS"
.IX Header "CONSTRUCTORS"
.IP "Authen::Passphrase::BlowfishCrypt\->new(\s-1ATTR\s0 => \s-1VALUE, ...\s0)" 4
.IX Item "Authen::Passphrase::BlowfishCrypt->new(ATTR => VALUE, ...)"
Generates a new passphrase recogniser object using the Blowfish-based
\&\fBcrypt()\fR algorithm.  The following attributes may be given:
.RS 4
.IP "\fBkey_nul\fR" 4
.IX Item "key_nul"
Truth value indicating whether to append a \s-1NUL\s0 to the passphrase 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 \s-1NUL\s0
is to be preferred.  Default true.
.IP "\fBcost\fR" 4
.IX Item "cost"
Base-two logarithm of the number of keying rounds to perform.
.IP "\fBkeying_nrounds_log2\fR" 4
.IX Item "keying_nrounds_log2"
Synonym for \fBcost\fR.
.IP "\fBsalt\fR" 4
.IX Item "salt"
The salt, as a 16\-byte string.
.IP "\fBsalt_base64\fR" 4
.IX Item "salt_base64"
The salt, as a string of 22 base 64 digits.
.IP "\fBsalt_random\fR" 4
.IX Item "salt_random"
Causes salt to be generated randomly.  The value given for this attribute
is ignored.  The source of randomness may be controlled by the facility
described in Data::Entropy.
.IP "\fBhash\fR" 4
.IX Item "hash"
The hash, as a 23\-byte string.
.IP "\fBhash_base64\fR" 4
.IX Item "hash_base64"
The hash, as a string of 31 base 64 digits.
.IP "\fBpassphrase\fR" 4
.IX Item "passphrase"
A passphrase that will be accepted.
.RE
.RS 4
.Sp
The cost and salt must be given, and either the hash or the passphrase.
.RE
.IP "Authen::Passphrase::BlowfishCrypt\->from_crypt(\s-1PASSWD\s0)" 4
.IX Item "Authen::Passphrase::BlowfishCrypt->from_crypt(PASSWD)"
Generates a new passphrase recogniser object using the Blowfish-based
\&\fBcrypt()\fR algorithm, from a crypt string.  The crypt string must start with
"\fB\f(CB$2\fB$\fR\*(L" for the version that does not append \s-1NUL\s0 to the key, or \*(R"\fB\f(CB$2a\fB$\fR\*(L"
for the version that does.  The next two characters must be decimal digits
giving the cost parameter.  This must be followed by \*(R"\fB$\fR", 22 base 64
digits giving the salt, and finally 31 base 64 digits giving the hash.
.IP "Authen::Passphrase::BlowfishCrypt\->from_rfc2307(\s-1USERPASSWORD\s0)" 4
.IX Item "Authen::Passphrase::BlowfishCrypt->from_rfc2307(USERPASSWORD)"
Generates a new passphrase recogniser object using the Blowfish-based
\&\fBcrypt()\fR algorithm, from an \s-1RFC 2307\s0 string.  The string must consist of
"\fB{\s-1CRYPT\s0}\fR" (case insensitive) followed by an acceptable crypt string.
.SH "METHODS"
.IX Header "METHODS"
.ie n .IP "$ppr\->key_nul" 4
.el .IP "\f(CW$ppr\fR\->key_nul" 4
.IX Item "$ppr->key_nul"
Returns a truth value indicating whether a \s-1NUL\s0 will be appended to the
passphrase before using it as a key.
.ie n .IP "$ppr\->cost" 4
.el .IP "\f(CW$ppr\fR\->cost" 4
.IX Item "$ppr->cost"
Returns the base-two logarithm of the number of keying rounds that will
be performed.
.ie n .IP "$ppr\->keying_nrounds_log2" 4
.el .IP "\f(CW$ppr\fR\->keying_nrounds_log2" 4
.IX Item "$ppr->keying_nrounds_log2"
Synonym for \*(L"cost\*(R".
.ie n .IP "$ppr\->salt" 4
.el .IP "\f(CW$ppr\fR\->salt" 4
.IX Item "$ppr->salt"
Returns the salt, as a string of sixteen bytes.
.ie n .IP "$ppr\->salt_base64" 4
.el .IP "\f(CW$ppr\fR\->salt_base64" 4
.IX Item "$ppr->salt_base64"
Returns the salt, as a string of 22 base 64 digits.
.ie n .IP "$ppr\->hash" 4
.el .IP "\f(CW$ppr\fR\->hash" 4
.IX Item "$ppr->hash"
Returns the hash value, as a string of 23 bytes.
.ie n .IP "$ppr\->hash_base64" 4
.el .IP "\f(CW$ppr\fR\->hash_base64" 4
.IX Item "$ppr->hash_base64"
Returns the hash value, as a string of 31 base 64 digits.
.ie n .IP "$ppr\->match(\s-1PASSPHRASE\s0)" 4
.el .IP "\f(CW$ppr\fR\->match(\s-1PASSPHRASE\s0)" 4
.IX Item "$ppr->match(PASSPHRASE)"
.PD 0
.ie n .IP "$ppr\->as_crypt" 4
.el .IP "\f(CW$ppr\fR\->as_crypt" 4
.IX Item "$ppr->as_crypt"
.ie n .IP "$ppr\->as_rfc2307" 4
.el .IP "\f(CW$ppr\fR\->as_rfc2307" 4
.IX Item "$ppr->as_rfc2307"
.PD
These methods are part of the standard Authen::Passphrase interface.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Authen::Passphrase,
Crypt::Eksblowfish::Bcrypt
.SH "AUTHOR"
.IX Header "AUTHOR"
Andrew Main (Zefram) <zefram@fysh.org>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2006, 2007, 2009, 2010, 2012
Andrew Main (Zefram) <zefram@fysh.org>
.SH "LICENSE"
.IX Header "LICENSE"
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.