1Authen::Passphrase::BloUwsfeirshCCornytprti(b3uptme)d PeArulthDeonc:u:mPeanstsapthiroanse::BlowfishCrypt(3pm)
2
6 Authen::Passphrase::BlowfishCrypt - passphrases using the
7 Blowfish-based Unix crypt()
8
10 use Authen::Passphrase::BlowfishCrypt;
11 $ppr = Authen::Passphrase::BlowfishCrypt->new(
13 cost => 8,
14 salt => "sodium__chloride",
15 hash_base64 => "BPZijhMHLvPeNMHd6XwZyNamOXVBTPi");
16 $ppr = Authen::Passphrase::BlowfishCrypt->new(
18 cost => 8, salt_random => 1,
19 passphrase => "passphrase");
20 $ppr = Authen::Passphrase::BlowfishCrypt->from_crypt(
22 '$2a$08$a07iYVTrVz7hYEvtakjiXOB'.
23 'PZijhMHLvPeNMHd6XwZyNamOXVBTPi');
24 $ppr = Authen::Passphrase::BlowfishCrypt->from_rfc2307(
26 '{CRYPT}$2a$08$a07iYVTrVz7hYEvtakjiXOB'.
27 'PZijhMHLvPeNMHd6XwZyNamOXVBTPi');
28 $key_nul = $ppr->key_nul;
30 $cost = $ppr->cost;
31 $cost = $ppr->keying_nrounds_log2;
32 $salt = $ppr->salt;
33 $salt_base64 = $ppr->salt_base64;
34 $hash = $ppr->hash;
35 $hash_base64 = $ppr->hash_base64;
36 if($ppr->match($passphrase)) { ...
38 $passwd = $ppr->as_crypt;
40 $userPassword = $ppr->as_rfc2307;
41
43 An object of this class encapsulates a passphrase hashed using the
44 Blowfish-based Unix crypt() hash function, known as "bcrypt". This is
45 a subclass of Authen::Passphrase, and this document assumes that the
46 reader is familiar with the documentation for that class.
47 The crypt() function in a modern Unix actually supports several
49 different passphrase schemes. This class is concerned only with one
50 particular scheme, a Blowfish-based algorithm designed by Niels Provos
51 and David Mazieres for OpenBSD. To handle the whole range of
52 passphrase schemes supported by the modern crypt(), see the from_crypt
53 constructor and the as_crypt method in Authen::Passphrase.
54 The Blowfish-based crypt() scheme uses a variant of Blowfish called
56 "Eksblowfish", for "expensive key schedule Blowfish". It has the
57 cryptographic strength of Blowfish, and a very slow key setup phase to
58 resist brute-force attacks. There is a "cost" parameter to the scheme:
59 the length of key setup is proportional to 2^cost. There is a 128-bit
60 salt. Up to 72 characters of the passphrase will be used; any more
61 will be ignored.
62 The cost, salt, and passphrase are all used to (very slowly) key
64 Eksblowfish. Once key setup is done, the string
65 "OrpheanBeholderScryDoubt" (three Blowfish blocks long) is encrypted 64
66 times in ECB mode. The final byte of the ciphertext is then dropped,
67 yielding a 23-byte hash.
68 In the crypt() function the salt and hash are represented in ASCII
70 using a base 64 encoding. The base 64 digits are ".", "/", "A" to "Z",
71 "a" to "z", "0" to "9" (in that order). The 16-byte salt is
72 represented as 22 base 64 digits, and the 23-byte hash as 31 base 64
73 digits.
74 This algorithm is intended for situations where the efficiency of a
76 brute force attack is a concern. It is suitable for use in new
77 applications where this requirement exists. If that is not a concern,
78 and it suffices to merely make brute force the most efficient attack,
79 see Authen::Passphrase::SaltedDigest for more efficient hash
80 algorithms.
81 Choice of the cost parameter is critical, due to the need to trade off
83 expense of brute-force attack against speed of legitimate passphrase
84 verification. A traditional target is that verification should take
85 about one second on widely-available hardware. (Algorithms that are
86 concerned about brute force speed but lack a cost parameter have often
87 aimed for this, with respect to hardware available at the time of the
88 algorithm's introduction.) As of 2011, this is achieved with a cost
89 parameter around 14.
90
92 Authen::Passphrase::BlowfishCrypt->new(ATTR => VALUE, ...)
93 Generates a new passphrase recogniser object using the Blowfish-
94 based crypt() algorithm. The following attributes may be given:
95 key_nul
97 Truth value indicating whether to append a NUL to the
98 passphrase before using it as a key. The algorithm as
99 originally devised does not do this, but it was later modified
100 to do it. The version that does append NUL is to be preferred.
101 Default true.
102 cost
104 Base-two logarithm of the number of keying rounds to perform.
105 keying_nrounds_log2
107 Synonym for cost.
108 salt
110 The salt, as a 16-byte string.
111 salt_base64
113 The salt, as a string of 22 base 64 digits.
114 salt_random
116 Causes salt to be generated randomly. The value given for this
117 attribute is ignored. The source of randomness may be
118 controlled by the facility described in Data::Entropy.
119 hash
121 The hash, as a 23-byte string.
122 hash_base64
124 The hash, as a string of 31 base 64 digits.
125 passphrase
127 A passphrase that will be accepted.
128 The cost and salt must be given, and either the hash or the
130 passphrase.
131 Authen::Passphrase::BlowfishCrypt->from_crypt(PASSWD)
133 Generates a new passphrase recogniser object using the Blowfish-
134 based crypt() algorithm, from a crypt string. The crypt string
135 must start with "$2$" for the version that does not append NUL to
136 the key, or "$2a$" for the version that does. The next two
137 characters must be decimal digits giving the cost parameter. This
138 must be followed by "$", 22 base 64 digits giving the salt, and
139 finally 31 base 64 digits giving the hash.
140 Authen::Passphrase::BlowfishCrypt->from_rfc2307(USERPASSWORD)
142 Generates a new passphrase recogniser object using the Blowfish-
143 based crypt() algorithm, from an RFC 2307 string. The string must
144 consist of "{CRYPT}" (case insensitive) followed by an acceptable
145 crypt string.
146
148 $ppr->key_nul
149 Returns a truth value indicating whether a NUL will be appended to
150 the passphrase before using it as a key.
151 $ppr->cost
153 Returns the base-two logarithm of the number of keying rounds that
154 will be performed.
155 $ppr->keying_nrounds_log2
157 Synonym for "cost".
158 $ppr->salt
160 Returns the salt, as a string of sixteen bytes.
161 $ppr->salt_base64
163 Returns the salt, as a string of 22 base 64 digits.
164 $ppr->hash
166 Returns the hash value, as a string of 23 bytes.
167 $ppr->hash_base64
169 Returns the hash value, as a string of 31 base 64 digits.
170 $ppr->match(PASSPHRASE)
172 $ppr->as_crypt
173 $ppr->as_rfc2307
174 These methods are part of the standard Authen::Passphrase
175 interface.
176
178 Authen::Passphrase, Crypt::Eksblowfish::Bcrypt
179
181 Andrew Main (Zefram) <zefram@fysh.org>
182
184 Copyright (C) 2006, 2007, 2009, 2010, 2012 Andrew Main (Zefram)
185 <zefram@fysh.org>
186
188 This module is free software; you can redistribute it and/or modify it
189 under the same terms as Perl itself.
190perl v5.38.0 2023-07A-u2t0hen::Passphrase::BlowfishCrypt(3pm)