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Upgrade to Digest 1.11 with a minor Pod fix. Also my first commit :)
[perl5.git] / lib / Digest.pm
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1package Digest;
2
3use strict;
4use vars qw($VERSION %MMAP $AUTOLOAD);
5
3cea4b92 6$VERSION = "1.11_01";
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7
8%MMAP = (
b12d758c 9 "SHA-1" => ["Digest::SHA1", ["Digest::SHA", 1], ["Digest::SHA2", 1]],
3cea4b92 10 "SHA-224" => [["Digest::SHA", 224]],
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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]],
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14 "HMAC-MD5" => "Digest::HMAC_MD5",
15 "HMAC-SHA-1" => "Digest::HMAC_SHA1",
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16 "CRC-16" => [["Digest::CRC", type => "crc16"]],
17 "CRC-32" => [["Digest::CRC", type => "crc32"]],
18 "CRC-CCITT" => [["Digest::CRC", type => "crcccitt"]],
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19);
20
21sub new
22{
23 shift; # class ignored
24 my $algorithm = shift;
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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, @_);
3357b1b1 44 }
b12d758c 45 die $err;
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46}
47
48sub AUTOLOAD
49{
50 my $class = shift;
51 my $algorithm = substr($AUTOLOAD, rindex($AUTOLOAD, '::')+2);
52 $class->new($algorithm, @_);
53}
54
551;
56
57__END__
58
59=head1 NAME
60
e19eb3c1 61Digest - Modules that calculate message digests
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62
63=head1 SYNOPSIS
64
e19eb3c1 65 $md5 = Digest->new("MD5");
3357b1b1 66 $sha1 = Digest->new("SHA-1");
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67 $sha256 = Digest->new("SHA-256");
68 $sha384 = Digest->new("SHA-384");
69 $sha512 = Digest->new("SHA-512");
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70
71 $hmac = Digest->HMAC_MD5($key);
72
73=head1 DESCRIPTION
74
75The C<Digest::> modules calculate digests, also called "fingerprints"
76or "hashes", of some data, called a message. The digest is (usually)
77some small/fixed size string. The actual size of the digest depend of
78the algorithm used. The message is simply a sequence of arbitrary
b12d758c 79bytes or bits.
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80
81An important property of the digest algorithms is that the digest is
82I<likely> to change if the message change in some way. Another
83property is that digest functions are one-way functions, i.e. it
84should be I<hard> to find a message that correspond to some given
85digest. Algorithms differ in how "likely" and how "hard", as well as
86how efficient they are to compute.
87
88All C<Digest::> modules provide the same programming interface. A
89functional interface for simple use, as well as an object oriented
90interface that can handle messages of arbitrary length and which can
91read files directly.
92
93The digest can be delivered in three formats:
94
95=over 8
96
97=item I<binary>
98
99This is the most compact form, but it is not well suited for printing
100or embedding in places that can't handle arbitrary data.
101
102=item I<hex>
103
e19eb3c1 104A twice as long string of lowercase hexadecimal digits.
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105
106=item I<base64>
107
108A string of portable printable characters. This is the base64 encoded
109representation of the digest with any trailing padding removed. The
110string will be about 30% longer than the binary version.
111L<MIME::Base64> tells you more about this encoding.
112
113=back
114
115
116The functional interface is simply importable functions with the same
117name as the algorithm. The functions take the message as argument and
118return the digest. Example:
119
120 use Digest::MD5 qw(md5);
121 $digest = md5($message);
122
123There are also versions of the functions with "_hex" or "_base64"
124appended to the name, which returns the digest in the indicated form.
125
126=head1 OO INTERFACE
127
128The following methods are available for all C<Digest::> modules:
129
130=over 4
131
132=item $ctx = Digest->XXX($arg,...)
133
134=item $ctx = Digest->new(XXX => $arg,...)
135
136=item $ctx = Digest::XXX->new($arg,...)
137
138The constructor returns some object that encapsulate the state of the
139message-digest algorithm. You can add data to the object and finally
140ask for the digest. The "XXX" should of course be replaced by the proper
141name of the digest algorithm you want to use.
142
143The two first forms are simply syntactic sugar which automatically
144load the right module on first use. The second form allow you to use
145algorithm names which contains letters which are not legal perl
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146identifiers, e.g. "SHA-1". If no implementation for the given algorithm
147can be found, then an exception is raised.
3357b1b1 148
67859229 149If new() is called as an instance method (i.e. $ctx->new) it will just
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150reset the state the object to the state of a newly created object. No
151new object is created in this case, and the return value is the
152reference to the object (i.e. $ctx).
153
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154=item $other_ctx = $ctx->clone
155
156The clone method creates a copy of the digest state object and returns
157a reference to the copy.
158
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159=item $ctx->reset
160
161This is just an alias for $ctx->new.
162
e19eb3c1 163=item $ctx->add( $data, ... )
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164
165The $data provided as argument are appended to the message we
166calculate the digest for. The return value is the $ctx object itself.
167
e19eb3c1 168=item $ctx->addfile( $io_handle )
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169
170The $io_handle is read until EOF and the content is appended to the
171message we calculate the digest for. The return value is the $ctx
172object itself.
173
e19eb3c1 174=item $ctx->add_bits( $data, $nbits )
b12d758c 175
e19eb3c1 176=item $ctx->add_bits( $bitstring )
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177
178The bits provided are appended to the message we calculate the digest
179for. The return value is the $ctx object itself.
180
181The two argument form of add_bits() will add the first $nbits bits
182from data. For the last potentially partial byte only the high order
183C<< $nbits % 8 >> bits are used. If $nbits is greater than C<<
184length($data) * 8 >>, then this method would do the same as C<<
185$ctx->add($data) >>, i.e. $nbits is silently ignored.
186
187The one argument form of add_bits() takes a $bitstring of "1" and "0"
188chars as argument. It's a shorthand for C<< $ctx->add_bits(pack("B*",
189$bitstring), length($bitstring)) >>.
190
191This example shows two calls that should have the same effect:
192
193 $ctx->add_bits("111100001010");
194 $ctx->add_bits("\xF0\xA0", 12);
195
196Most digest algorithms are byte based. For those it is not possible
197to add bits that are not a multiple of 8, and the add_bits() method
198will croak if you try.
199
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200=item $ctx->digest
201
202Return the binary digest for the message.
203
204Note that the C<digest> operation is effectively a destructive,
205read-once operation. Once it has been performed, the $ctx object is
206automatically C<reset> and can be used to calculate another digest
70ee4409 207value. Call $ctx->clone->digest if you want to calculate the digest
3c4b39be 208without resetting the digest state.
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209
210=item $ctx->hexdigest
211
212Same as $ctx->digest, but will return the digest in hexadecimal form.
213
214=item $ctx->b64digest
215
216Same as $ctx->digest, but will return the digest as a base64 encoded
217string.
218
219=back
220
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221=head1 Digest speed
222
223This table should give some indication on the relative speed of
224different algorithms. It is sorted by throughput based on a benchmark
225done with of some implementations of this API:
226
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227 Algorithm Size Implementation MB/s
228
229 MD4 128 Digest::MD4 v1.3 165.0
230 MD5 128 Digest::MD5 v2.33 98.8
231 SHA-256 256 Digest::SHA2 v1.1.0 66.7
232 SHA-1 160 Digest::SHA v4.3.1 58.9
233 SHA-1 160 Digest::SHA1 v2.10 48.8
234 SHA-256 256 Digest::SHA v4.3.1 41.3
235 Haval-256 256 Digest::Haval256 v1.0.4 39.8
236 SHA-384 384 Digest::SHA2 v1.1.0 19.6
237 SHA-512 512 Digest::SHA2 v1.1.0 19.3
238 SHA-384 384 Digest::SHA v4.3.1 19.2
239 SHA-512 512 Digest::SHA v4.3.1 19.2
240 Whirlpool 512 Digest::Whirlpool v1.0.2 13.0
241 MD2 128 Digest::MD2 v2.03 9.5
242
243 Adler-32 32 Digest::Adler32 v0.03 1.3
244 CRC-16 16 Digest::CRC v0.05 1.1
245 CRC-32 32 Digest::CRC v0.05 1.1
246 MD5 128 Digest::Perl::MD5 v1.5 1.0
247 CRC-CCITT 16 Digest::CRC v0.05 0.8
248
249These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running
250under Linux on a P4 2.8 GHz CPU. The last 5 entries differ by being
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251pure perl implementations of the algorithms, which explains why they
252are so slow.
253
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254=head1 SEE ALSO
255
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256L<Digest::Adler32>, L<Digest::CRC>, L<Digest::Haval256>,
257L<Digest::HMAC>, L<Digest::MD2>, L<Digest::MD4>, L<Digest::MD5>,
258L<Digest::SHA>, L<Digest::SHA1>, L<Digest::SHA2>, L<Digest::Whirlpool>
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259
260New digest implementations should consider subclassing from L<Digest::base>.
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261
262L<MIME::Base64>
263
264=head1 AUTHOR
265
266Gisle Aas <gisle@aas.no>
267
268The C<Digest::> interface is based on the interface originally
269developed by Neil Winton for his C<MD5> module.
270
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271This library is free software; you can redistribute it and/or
272modify it under the same terms as Perl itself.
273
897ff129 274 Copyright 1998-2001,2003-2004 Gisle Aas.
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275 Copyright 1995-1996 Neil Winton.
276
3357b1b1 277=cut