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920dae64 AT |
1 | package Digest; |
2 | ||
3 | use strict; | |
4 | use vars qw($VERSION %MMAP $AUTOLOAD); | |
5 | ||
6 | $VERSION = "1.14"; | |
7 | ||
8 | %MMAP = ( | |
9 | "SHA-1" => ["Digest::SHA1", ["Digest::SHA", 1], ["Digest::SHA2", 1]], | |
10 | "SHA-224" => [["Digest::SHA", 224]], | |
11 | "SHA-256" => [["Digest::SHA", 256], ["Digest::SHA2", 256]], | |
12 | "SHA-384" => [["Digest::SHA", 384], ["Digest::SHA2", 384]], | |
13 | "SHA-512" => [["Digest::SHA", 512], ["Digest::SHA2", 512]], | |
14 | "HMAC-MD5" => "Digest::HMAC_MD5", | |
15 | "HMAC-SHA-1" => "Digest::HMAC_SHA1", | |
16 | "CRC-16" => [["Digest::CRC", type => "crc16"]], | |
17 | "CRC-32" => [["Digest::CRC", type => "crc32"]], | |
18 | "CRC-CCITT" => [["Digest::CRC", type => "crcccitt"]], | |
19 | ); | |
20 | ||
21 | sub new | |
22 | { | |
23 | shift; # class ignored | |
24 | my $algorithm = shift; | |
25 | my $impl = $MMAP{$algorithm} || do { | |
26 | $algorithm =~ s/\W+//; | |
27 | "Digest::$algorithm"; | |
28 | }; | |
29 | $impl = [$impl] unless ref($impl); | |
30 | my $err; | |
31 | for (@$impl) { | |
32 | my $class = $_; | |
33 | my @args; | |
34 | ($class, @args) = @$class if ref($class); | |
35 | no strict 'refs'; | |
36 | unless (exists ${"$class\::"}{"VERSION"}) { | |
37 | eval "require $class"; | |
38 | if ($@) { | |
39 | $err ||= $@; | |
40 | next; | |
41 | } | |
42 | } | |
43 | return $class->new(@args, @_); | |
44 | } | |
45 | die $err; | |
46 | } | |
47 | ||
48 | sub AUTOLOAD | |
49 | { | |
50 | my $class = shift; | |
51 | my $algorithm = substr($AUTOLOAD, rindex($AUTOLOAD, '::')+2); | |
52 | $class->new($algorithm, @_); | |
53 | } | |
54 | ||
55 | 1; | |
56 | ||
57 | __END__ | |
58 | ||
59 | =head1 NAME | |
60 | ||
61 | Digest - Modules that calculate message digests | |
62 | ||
63 | =head1 SYNOPSIS | |
64 | ||
65 | $md5 = Digest->new("MD5"); | |
66 | $sha1 = Digest->new("SHA-1"); | |
67 | $sha256 = Digest->new("SHA-256"); | |
68 | $sha384 = Digest->new("SHA-384"); | |
69 | $sha512 = Digest->new("SHA-512"); | |
70 | ||
71 | $hmac = Digest->HMAC_MD5($key); | |
72 | ||
73 | =head1 DESCRIPTION | |
74 | ||
75 | The C<Digest::> modules calculate digests, also called "fingerprints" | |
76 | or "hashes", of some data, called a message. The digest is (usually) | |
77 | some small/fixed size string. The actual size of the digest depend of | |
78 | the algorithm used. The message is simply a sequence of arbitrary | |
79 | bytes or bits. | |
80 | ||
81 | An important property of the digest algorithms is that the digest is | |
82 | I<likely> to change if the message change in some way. Another | |
83 | property is that digest functions are one-way functions, that is it | |
84 | should be I<hard> to find a message that correspond to some given | |
85 | digest. Algorithms differ in how "likely" and how "hard", as well as | |
86 | how efficient they are to compute. | |
87 | ||
88 | Note that the properties of the algorithms change over time, as the | |
89 | algorithms are analyzed and machines grow faster. If your application | |
90 | for instance depends on it being "impossible" to generate the same | |
91 | digest for a different message it is wise to make it easy to plug in | |
92 | stronger algorithms as the one used grow weaker. Using the interface | |
93 | documented here should make it easy to change algorithms later. | |
94 | ||
95 | All C<Digest::> modules provide the same programming interface. A | |
96 | functional interface for simple use, as well as an object oriented | |
97 | interface that can handle messages of arbitrary length and which can | |
98 | read files directly. | |
99 | ||
100 | The digest can be delivered in three formats: | |
101 | ||
102 | =over 8 | |
103 | ||
104 | =item I<binary> | |
105 | ||
106 | This is the most compact form, but it is not well suited for printing | |
107 | or embedding in places that can't handle arbitrary data. | |
108 | ||
109 | =item I<hex> | |
110 | ||
111 | A twice as long string of lowercase hexadecimal digits. | |
112 | ||
113 | =item I<base64> | |
114 | ||
115 | A string of portable printable characters. This is the base64 encoded | |
116 | representation of the digest with any trailing padding removed. The | |
117 | string will be about 30% longer than the binary version. | |
118 | L<MIME::Base64> tells you more about this encoding. | |
119 | ||
120 | =back | |
121 | ||
122 | ||
123 | The functional interface is simply importable functions with the same | |
124 | name as the algorithm. The functions take the message as argument and | |
125 | return the digest. Example: | |
126 | ||
127 | use Digest::MD5 qw(md5); | |
128 | $digest = md5($message); | |
129 | ||
130 | There are also versions of the functions with "_hex" or "_base64" | |
131 | appended to the name, which returns the digest in the indicated form. | |
132 | ||
133 | =head1 OO INTERFACE | |
134 | ||
135 | The following methods are available for all C<Digest::> modules: | |
136 | ||
137 | =over 4 | |
138 | ||
139 | =item $ctx = Digest->XXX($arg,...) | |
140 | ||
141 | =item $ctx = Digest->new(XXX => $arg,...) | |
142 | ||
143 | =item $ctx = Digest::XXX->new($arg,...) | |
144 | ||
145 | The constructor returns some object that encapsulate the state of the | |
146 | message-digest algorithm. You can add data to the object and finally | |
147 | ask for the digest. The "XXX" should of course be replaced by the proper | |
148 | name of the digest algorithm you want to use. | |
149 | ||
150 | The two first forms are simply syntactic sugar which automatically | |
151 | load the right module on first use. The second form allow you to use | |
152 | algorithm names which contains letters which are not legal perl | |
153 | identifiers, e.g. "SHA-1". If no implementation for the given algorithm | |
154 | can be found, then an exception is raised. | |
155 | ||
156 | If new() is called as an instance method (i.e. $ctx->new) it will just | |
157 | reset the state the object to the state of a newly created object. No | |
158 | new object is created in this case, and the return value is the | |
159 | reference to the object (i.e. $ctx). | |
160 | ||
161 | =item $other_ctx = $ctx->clone | |
162 | ||
163 | The clone method creates a copy of the digest state object and returns | |
164 | a reference to the copy. | |
165 | ||
166 | =item $ctx->reset | |
167 | ||
168 | This is just an alias for $ctx->new. | |
169 | ||
170 | =item $ctx->add( $data, ... ) | |
171 | ||
172 | The $data provided as argument are appended to the message we | |
173 | calculate the digest for. The return value is the $ctx object itself. | |
174 | ||
175 | =item $ctx->addfile( $io_handle ) | |
176 | ||
177 | The $io_handle is read until EOF and the content is appended to the | |
178 | message we calculate the digest for. The return value is the $ctx | |
179 | object itself. | |
180 | ||
181 | =item $ctx->add_bits( $data, $nbits ) | |
182 | ||
183 | =item $ctx->add_bits( $bitstring ) | |
184 | ||
185 | The bits provided are appended to the message we calculate the digest | |
186 | for. The return value is the $ctx object itself. | |
187 | ||
188 | The two argument form of add_bits() will add the first $nbits bits | |
189 | from data. For the last potentially partial byte only the high order | |
190 | C<< $nbits % 8 >> bits are used. If $nbits is greater than C<< | |
191 | length($data) * 8 >>, then this method would do the same as C<< | |
192 | $ctx->add($data) >>, that is $nbits is silently ignored. | |
193 | ||
194 | The one argument form of add_bits() takes a $bitstring of "1" and "0" | |
195 | chars as argument. It's a shorthand for C<< $ctx->add_bits(pack("B*", | |
196 | $bitstring), length($bitstring)) >>. | |
197 | ||
198 | This example shows two calls that should have the same effect: | |
199 | ||
200 | $ctx->add_bits("111100001010"); | |
201 | $ctx->add_bits("\xF0\xA0", 12); | |
202 | ||
203 | Most digest algorithms are byte based. For those it is not possible | |
204 | to add bits that are not a multiple of 8, and the add_bits() method | |
205 | will croak if you try. | |
206 | ||
207 | =item $ctx->digest | |
208 | ||
209 | Return the binary digest for the message. | |
210 | ||
211 | Note that the C<digest> operation is effectively a destructive, | |
212 | read-once operation. Once it has been performed, the $ctx object is | |
213 | automatically C<reset> and can be used to calculate another digest | |
214 | value. Call $ctx->clone->digest if you want to calculate the digest | |
215 | without reseting the digest state. | |
216 | ||
217 | =item $ctx->hexdigest | |
218 | ||
219 | Same as $ctx->digest, but will return the digest in hexadecimal form. | |
220 | ||
221 | =item $ctx->b64digest | |
222 | ||
223 | Same as $ctx->digest, but will return the digest as a base64 encoded | |
224 | string. | |
225 | ||
226 | =back | |
227 | ||
228 | =head1 Digest speed | |
229 | ||
230 | This table should give some indication on the relative speed of | |
231 | different algorithms. It is sorted by throughput based on a benchmark | |
232 | done with of some implementations of this API: | |
233 | ||
234 | Algorithm Size Implementation MB/s | |
235 | ||
236 | MD4 128 Digest::MD4 v1.3 165.0 | |
237 | MD5 128 Digest::MD5 v2.33 98.8 | |
238 | SHA-256 256 Digest::SHA2 v1.1.0 66.7 | |
239 | SHA-1 160 Digest::SHA v4.3.1 58.9 | |
240 | SHA-1 160 Digest::SHA1 v2.10 48.8 | |
241 | SHA-256 256 Digest::SHA v4.3.1 41.3 | |
242 | Haval-256 256 Digest::Haval256 v1.0.4 39.8 | |
243 | SHA-384 384 Digest::SHA2 v1.1.0 19.6 | |
244 | SHA-512 512 Digest::SHA2 v1.1.0 19.3 | |
245 | SHA-384 384 Digest::SHA v4.3.1 19.2 | |
246 | SHA-512 512 Digest::SHA v4.3.1 19.2 | |
247 | Whirlpool 512 Digest::Whirlpool v1.0.2 13.0 | |
248 | MD2 128 Digest::MD2 v2.03 9.5 | |
249 | ||
250 | Adler-32 32 Digest::Adler32 v0.03 1.3 | |
251 | CRC-16 16 Digest::CRC v0.05 1.1 | |
252 | CRC-32 32 Digest::CRC v0.05 1.1 | |
253 | MD5 128 Digest::Perl::MD5 v1.5 1.0 | |
254 | CRC-CCITT 16 Digest::CRC v0.05 0.8 | |
255 | ||
256 | These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running | |
257 | under Linux on a P4 2.8 GHz CPU. The last 5 entries differ by being | |
258 | pure perl implementations of the algorithms, which explains why they | |
259 | are so slow. | |
260 | ||
261 | =head1 SEE ALSO | |
262 | ||
263 | L<Digest::Adler32>, L<Digest::CRC>, L<Digest::Haval256>, | |
264 | L<Digest::HMAC>, L<Digest::MD2>, L<Digest::MD4>, L<Digest::MD5>, | |
265 | L<Digest::SHA>, L<Digest::SHA1>, L<Digest::SHA2>, L<Digest::Whirlpool> | |
266 | ||
267 | New digest implementations should consider subclassing from L<Digest::base>. | |
268 | ||
269 | L<MIME::Base64> | |
270 | ||
271 | =head1 AUTHOR | |
272 | ||
273 | Gisle Aas <gisle@aas.no> | |
274 | ||
275 | The C<Digest::> interface is based on the interface originally | |
276 | developed by Neil Winton for his C<MD5> module. | |
277 | ||
278 | This library is free software; you can redistribute it and/or | |
279 | modify it under the same terms as Perl itself. | |
280 | ||
281 | Copyright 1998-2001,2003-2004 Gisle Aas. | |
282 | Copyright 1995-1996 Neil Winton. | |
283 | ||
284 | =cut |