1Crypt::PBKDF2(3) User Contributed Perl Documentation Crypt::PBKDF2(3)
2
6 Crypt::PBKDF2 - The PBKDF2 password hashing algorithm.
7
9 version 0.161520
10
12 use Crypt::PBKDF2;
13 my $pbkdf2 = Crypt::PBKDF2->new(
15 hash_class => 'HMACSHA1', # this is the default
16 iterations => 1000, # so is this
17 output_len => 20, # and this
18 salt_len => 4, # and this.
19 );
20 my $hash = $pbkdf2->generate("s3kr1t_password");
22 if ($pbkdf2->validate($hash, "s3kr1t_password")) {
23 access_granted();
24 }
25
27 PBKDF2 is a secure password hashing algorithm that uses the techniques
28 of "key strengthening" to make the complexity of a brute-force attack
29 arbitrarily high. PBKDF2 uses any other cryptographic hash or cipher
30 (by convention, usually HMAC-SHA1, but "Crypt::PBKDF2" is fully
31 pluggable), and allows for an arbitrary number of iterations of the
32 hashing function, and a nearly unlimited output hash size (up to 2**32
33 - 1 times the size of the output of the backend hash). The hash is
34 salted, as any password hash should be, and the salt may also be of
35 arbitrary size.
36
38 hash_class
39 Type: String, Default: HMACSHA1
40 The name of the default class that will provide PBKDF2's Pseudo-Random
42 Function (the backend hash). If the value starts with a "+", the "+"
43 will be removed and the remainder will be taken as a fully-qualified
44 package name. Otherwise, the value will be appended to
45 "Crypt::PBKDF2::Hash::".
46 hash_args
48 Type: HashRef, Default: {}
49 Arguments to be passed to the "hash_class" constructor.
51 hasher
53 Type: Object (must fulfill role Crypt::PBKDF2::Hash), Default: None.
54 It is also possible to provide a hash object directly; in this case the
56 "hash_class" and "hash_args" are ignored.
57 iterations
59 Type: Integer, Default: 1000.
60 The default number of iterations of the hashing function to use for the
62 "generate" and "PBKDF2" methods.
63 output_len
65 Type: Integer.
66 The default size (in bytes, not bits) of the output hash. If a value
68 isn't provided, the output size depends on the "hash_class" / "hasher"
69 selected, and will equal the output size of the backend hash (e.g. 20
70 bytes for HMACSHA1).
71 salt_len
73 Type: Integer, Default: 4
74 The default salt length (in bytes) for the "generate" method.
76 encoding
78 Type: String (either "crypt" or "ldap"), Default: "ldap"
79 The hash format to generate. The "ldap" format is intended to be
81 compatible with RFC2307, and looks like:
82 {X-PBKDF2}HMACSHA1:AAAD6A:8ODUPA==:1HSdSVVwlWSZhbPGO7GIZ4iUbrk=
84 While the "crypt" format is similar to the format used by the "crypt()"
86 function, except with more structured information in the second (salt)
87 field. It looks like:
88 $PBKDF2$HMACSHA1:1000:4q9OTg==$9Pb6bCRgnct/dga+4v4Lyv8x31s=
90 Versions of this module up to 0.110461 generated the "crypt" format, so
92 set that if you want it. Current versions of this module will read
93 either format, but the "ldap" format is preferred.
94 length_limit
96 Type: Integer
97 The maximum password length to allow, for generate and verify
99 functions. Allowing passwords of unlimited length can allow a denial-
100 of-service attack in which an attacker asks the server to validate very
101 large passwords.
102 For compatibility this attribute is unset by default, but it is
104 recommended to set it to a reasonably small value like 100 -- large
105 enough that users aren't discouraged from having secure passwords, but
106 small enough to limit the computation needed to validate any one
107 password.
108
110 generate ($password, [$salt])
111 Generates a hash for the given $password. If $salt is not provided, a
112 random salt with length "salt_len" will be generated.
113 There are two output formats available, depending on the setting of the
115 "encoding" attribute: "ldap" and "crypt"; see the documentation for
116 "encoding" for more information.
117 validate ($hashed, $password)
119 Validates whether the password $password matches the hash string
120 $hashed. May throw an exception if the format of $hashed is invalid;
121 otherwise, returns true or false. Accepts both formats that the
122 "generate" method can produce.
123 PBKDF2 ($salt, $password)
125 The raw PBKDF2 algorithm. Given the $salt and $password, returns the
126 raw binary hash.
127 PBKDF2_base64 ($salt, $password)
129 As the "PBKDF2" method, only the output is encoded with MIME::Base64.
130 PBKDF2_hex ($salt, $password)
132 As the "PBKDF2" method, only the output is encoded in hexadecimal.
133 encode_string ($salt, $hash)
135 Given a generated salt and hash, hash, generates output in the form
136 generated by "generate" and accepted by "validate". Unlikely to be of
137 much use to anyone else.
138 decode_string ($hashed)
140 Given a textual hash in the form generated by "generate", decodes it
141 and returns a HashRef containing:
142 • "algorithm": A string representing the hash algorithm used. See
144 "hasher_from_algorithm ($algo_str)".
145 • "iterations": The number of iterations used.
147 • "salt": The salt, in raw binary form.
149 • "hash": The hash, in raw binary form.
151 This method is mostly for internal use, but it has been left public as
153 it may come in handy. If the input data is invalid, this method may
154 throw an exception.
155 hasher_from_algorithm ($algo_str)
157 Attempts to load and instantiate a "Crypt::PBKDF2::Hash::*" class based
158 on an algorithm string as produced by "encode_string" / "generate".
159 clone (%params)
161 Create a new object like this one, but with %params changed.
162
164 • Wikipedia: PBKDF2: <http://en.wikipedia.org/wiki/PBKDF2>
165 • RFC2898, PKCS#5 version 2.0: <http://tools.ietf.org/html/rfc2898>
167 • RFC2307, Using LDAP as a Network Information Service:
169 <http://tools.ietf.org/html/rfc2307>
170
172 Andrew Rodland <arodland@cpan.org>
173
175 This software is copyright (c) 2016 by Andrew Rodland.
176 This is free software; you can redistribute it and/or modify it under
178 the same terms as the Perl 5 programming language system itself.
179perl v5.34.0 2021-07-22 Crypt::PBKDF2(3)