lib/perl5/5.8.8/Digest.pm

   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