perl/lib/Digest.pm

package Digest;

use strict;
use vars qw($VERSION %MMAP $AUTOLOAD);

$VERSION = "1.10";

%MMAP = (
  "SHA-1"      => ["Digest::SHA1", ["Digest::SHA", 1], ["Digest::SHA2", 1]],
  "SHA-256"    => [["Digest::SHA", 256], ["Digest::SHA2", 256]],
  "SHA-384"    => [["Digest::SHA", 384], ["Digest::SHA2", 384]],
  "SHA-512"    => [["Digest::SHA", 512], ["Digest::SHA2", 512]],
  "HMAC-MD5"   => "Digest::HMAC_MD5",
  "HMAC-SHA-1" => "Digest::HMAC_SHA1",
  "CRC-16"     => [["Digest::CRC", type => "crc16"]],
  "CRC-32"     => [["Digest::CRC", type => "crc32"]],
  "CRC-CCITT"  => [["Digest::CRC", type => "crcccitt"]],
);

sub new
{
    shift;  # class ignored
    my $algorithm = shift;
    my $impl = $MMAP{$algorithm} || do {
        $algorithm =~ s/\W+//;
        "Digest::$algorithm";
    };
    $impl = [$impl] unless ref($impl);
    my $err;
    for  (@$impl) {
        my $class = $_;
        my @args;
        ($class, @args) = @$class if ref($class);
        no strict 'refs';
        unless (exists ${"$class\::"}{"VERSION"}) {
            eval "require $class";
            if ($@) {
                $err ||= $@;
                next;
            }
        }
        return $class->new(@args, @_);
    }
    die $err;
}

sub AUTOLOAD
{
    my $class = shift;
    my $algorithm = substr($AUTOLOAD, rindex($AUTOLOAD, '::')+2);
    $class->new($algorithm, @_);
}

1;

__END__

=head1 NAME

Digest - Modules that calculate message digests

=head1 SYNOPSIS

  $md5  = Digest->new("MD5");
  $sha1 = Digest->new("SHA-1");
  $sha256 = Digest->new("SHA-256");
  $sha384 = Digest->new("SHA-384");
  $sha512 = Digest->new("SHA-512");

  $hmac = Digest->HMAC_MD5($key);

=head1 DESCRIPTION

The C<Digest::> modules calculate digests, also called "fingerprints"
or "hashes", of some data, called a message.  The digest is (usually)
some small/fixed size string.  The actual size of the digest depend of
the algorithm used.  The message is simply a sequence of arbitrary
bytes or bits.

An important property of the digest algorithms is that the digest is
I<likely> to change if the message change in some way.  Another
property is that digest functions are one-way functions, i.e. it
should be I<hard> to find a message that correspond to some given
digest.  Algorithms differ in how "likely" and how "hard", as well as
how efficient they are to compute.

All C<Digest::> modules provide the same programming interface.  A
functional interface for simple use, as well as an object oriented
interface that can handle messages of arbitrary length and which can
read files directly.

The digest can be delivered in three formats:

=over 8

=item I<binary>

This is the most compact form, but it is not well suited for printing
or embedding in places that can't handle arbitrary data.

=item I<hex>

A twice as long string of lowercase hexadecimal digits.

=item I<base64>

A string of portable printable characters.  This is the base64 encoded
representation of the digest with any trailing padding removed.  The
string will be about 30% longer than the binary version.
L<MIME::Base64> tells you more about this encoding.

=back


The functional interface is simply importable functions with the same
name as the algorithm.  The functions take the message as argument and
return the digest.  Example:

  use Digest::MD5 qw(md5);
  $digest = md5($message);

There are also versions of the functions with "_hex" or "_base64"
appended to the name, which returns the digest in the indicated form.

=head1 OO INTERFACE

The following methods are available for all C<Digest::> modules:

=over 4

=item $ctx = Digest->XXX($arg,...)

=item $ctx = Digest->new(XXX => $arg,...)

=item $ctx = Digest::XXX->new($arg,...)

The constructor returns some object that encapsulate the state of the
message-digest algorithm.  You can add data to the object and finally
ask for the digest.  The "XXX" should of course be replaced by the proper
name of the digest algorithm you want to use.

The two first forms are simply syntactic sugar which automatically
load the right module on first use.  The second form allow you to use
algorithm names which contains letters which are not legal perl
identifiers, e.g. "SHA-1".  If no implementation for the given algorithm
can be found, then an exception is raised.

If new() is called as an instance method (i.e. $ctx->new) it will just
reset the state the object to the state of a newly created object.  No
new object is created in this case, and the return value is the
reference to the object (i.e. $ctx).

=item $other_ctx = $ctx->clone

The clone method creates a copy of the digest state object and returns
a reference to the copy.

=item $ctx->reset

This is just an alias for $ctx->new.

=item $ctx->add( $data, ... )

The $data provided as argument are appended to the message we
calculate the digest for.  The return value is the $ctx object itself.

=item $ctx->addfile( $io_handle )

The $io_handle is read until EOF and the content is appended to the
message we calculate the digest for.  The return value is the $ctx
object itself.

=item $ctx->add_bits( $data, $nbits )

=item $ctx->add_bits( $bitstring )

The bits provided are appended to the message we calculate the digest
for.  The return value is the $ctx object itself.

The two argument form of add_bits() will add the first $nbits bits
from data.  For the last potentially partial byte only the high order
C<< $nbits % 8 >> bits are used.  If $nbits is greater than C<<
length($data) * 8 >>, then this method would do the same as C<<
$ctx->add($data) >>, i.e. $nbits is silently ignored.

The one argument form of add_bits() takes a $bitstring of "1" and "0"
chars as argument.  It's a shorthand for C<< $ctx->add_bits(pack("B*",
$bitstring), length($bitstring)) >>.

This example shows two calls that should have the same effect:

   $ctx->add_bits("111100001010");
   $ctx->add_bits("\xF0\xA0", 12);

Most digest algorithms are byte based.  For those it is not possible
to add bits that are not a multiple of 8, and the add_bits() method
will croak if you try.

=item $ctx->digest

Return the binary digest for the message.

Note that the C<digest> operation is effectively a destructive,
read-once operation. Once it has been performed, the $ctx object is
automatically C<reset> and can be used to calculate another digest
value.  Call $ctx->clone->digest if you want to calculate the digest
without reseting the digest state.

=item $ctx->hexdigest

Same as $ctx->digest, but will return the digest in hexadecimal form.

=item $ctx->b64digest

Same as $ctx->digest, but will return the digest as a base64 encoded
string.

=back

=head1 Digest speed

This table should give some indication on the relative speed of
different algorithms.  It is sorted by throughput based on a benchmark
done with of some implementations of this API:

 Algorithm      Size    Implementation                  MB/s

 MD4            128     Digest::MD4 v1.3               165.0
 MD5            128     Digest::MD5 v2.33               98.8
 SHA-256        256     Digest::SHA2 v1.1.0             66.7
 SHA-1          160     Digest::SHA v4.3.1              58.9
 SHA-1          160     Digest::SHA1 v2.10              48.8
 SHA-256        256     Digest::SHA v4.3.1              41.3
 Haval-256      256     Digest::Haval256 v1.0.4         39.8
 SHA-384        384     Digest::SHA2 v1.1.0             19.6
 SHA-512        512     Digest::SHA2 v1.1.0             19.3
 SHA-384        384     Digest::SHA v4.3.1              19.2
 SHA-512        512     Digest::SHA v4.3.1              19.2
 Whirlpool      512     Digest::Whirlpool v1.0.2        13.0
 MD2            128     Digest::MD2 v2.03                9.5

 Adler-32        32     Digest::Adler32 v0.03            1.3
 CRC-16          16     Digest::CRC v0.05                1.1
 CRC-32          32     Digest::CRC v0.05                1.1
 MD5            128     Digest::Perl::MD5 v1.5           1.0
 CRC-CCITT       16     Digest::CRC v0.05                0.8

These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running
under Linux on a P4 2.8 GHz CPU.  The last 5 entries differ by being
pure perl implementations of the algorithms, which explains why they
are so slow.

=head1 SEE ALSO

L<Digest::Adler32>, L<Digest::CRC>, L<Digest::Haval256>,
L<Digest::HMAC>, L<Digest::MD2>, L<Digest::MD4>, L<Digest::MD5>,
L<Digest::SHA>, L<Digest::SHA1>, L<Digest::SHA2>, L<Digest::Whirlpool>

New digest implementations should consider subclassing from L<Digest::base>.

L<MIME::Base64>

=head1 AUTHOR

Gisle Aas <gisle@aas.no>

The C<Digest::> interface is based on the interface originally
developed by Neil Winton for his C<MD5> module.

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

    Copyright 1998-2001,2003-2004 Gisle Aas.
    Copyright 1995-1996 Neil Winton.

=cut
Revision:	1.1
Committed:	Thu Jun 30 14:27:08 2005 UTC (21 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Digest;
2
3			use strict;
4			use vars qw($VERSION %MMAP $AUTOLOAD);
5
6			$VERSION = "1.10";
7
8			%MMAP = (
9			"SHA-1" => ["Digest::SHA1", ["Digest::SHA", 1], ["Digest::SHA2", 1]],
10			"SHA-256" => [["Digest::SHA", 256], ["Digest::SHA2", 256]],
11			"SHA-384" => [["Digest::SHA", 384], ["Digest::SHA2", 384]],
12			"SHA-512" => [["Digest::SHA", 512], ["Digest::SHA2", 512]],
13			"HMAC-MD5" => "Digest::HMAC_MD5",
14			"HMAC-SHA-1" => "Digest::HMAC_SHA1",
15			"CRC-16" => [["Digest::CRC", type => "crc16"]],
16			"CRC-32" => [["Digest::CRC", type => "crc32"]],
17			"CRC-CCITT" => [["Digest::CRC", type => "crcccitt"]],
18			);
19
20			sub new
21			{
22			shift; # class ignored
23			my $algorithm = shift;
24			my $impl = $MMAP{$algorithm} \|\| do {
25			$algorithm =~ s/\W+//;
26			"Digest::$algorithm";
27			};
28			$impl = [$impl] unless ref($impl);
29			my $err;
30			for (@$impl) {
31			my $class = $_;
32			my @args;
33			($class, @args) = @$class if ref($class);
34			no strict 'refs';
35			unless (exists ${"$class\::"}{"VERSION"}) {
36			eval "require $class";
37			if ($@) {
38			$err \|\|= $@;
39			next;
40			}
41			}
42			return $class->new(@args, @_);
43			}
44			die $err;
45			}
46
47			sub AUTOLOAD
48			{
49			my $class = shift;
50			my $algorithm = substr($AUTOLOAD, rindex($AUTOLOAD, '::')+2);
51			$class->new($algorithm, @_);
52			}
53
54			1;
55
56			__END__
57
58			=head1 NAME
59
60			Digest - Modules that calculate message digests
61
62			=head1 SYNOPSIS
63
64			$md5 = Digest->new("MD5");
65			$sha1 = Digest->new("SHA-1");
66			$sha256 = Digest->new("SHA-256");
67			$sha384 = Digest->new("SHA-384");
68			$sha512 = Digest->new("SHA-512");
69
70			$hmac = Digest->HMAC_MD5($key);
71
72			=head1 DESCRIPTION
73
74			The C<Digest::> modules calculate digests, also called "fingerprints"
75			or "hashes", of some data, called a message. The digest is (usually)
76			some small/fixed size string. The actual size of the digest depend of
77			the algorithm used. The message is simply a sequence of arbitrary
78			bytes or bits.
79
80			An important property of the digest algorithms is that the digest is
81			I<likely> to change if the message change in some way. Another
82			property is that digest functions are one-way functions, i.e. it
83			should be I<hard> to find a message that correspond to some given
84			digest. Algorithms differ in how "likely" and how "hard", as well as
85			how efficient they are to compute.
86
87			All C<Digest::> modules provide the same programming interface. A
88			functional interface for simple use, as well as an object oriented
89			interface that can handle messages of arbitrary length and which can
90			read files directly.
91
92			The digest can be delivered in three formats:
93
94			=over 8
95
96			=item I<binary>
97
98			This is the most compact form, but it is not well suited for printing
99			or embedding in places that can't handle arbitrary data.
100
101			=item I<hex>
102
103			A twice as long string of lowercase hexadecimal digits.
104
105			=item I<base64>
106
107			A string of portable printable characters. This is the base64 encoded
108			representation of the digest with any trailing padding removed. The
109			string will be about 30% longer than the binary version.
110			L<MIME::Base64> tells you more about this encoding.
111
112			=back
113
114
115			The functional interface is simply importable functions with the same
116			name as the algorithm. The functions take the message as argument and
117			return the digest. Example:
118
119			use Digest::MD5 qw(md5);
120			$digest = md5($message);
121
122			There are also versions of the functions with "_hex" or "_base64"
123			appended to the name, which returns the digest in the indicated form.
124
125			=head1 OO INTERFACE
126
127			The following methods are available for all C<Digest::> modules:
128
129			=over 4
130
131			=item $ctx = Digest->XXX($arg,...)
132
133			=item $ctx = Digest->new(XXX => $arg,...)
134
135			=item $ctx = Digest::XXX->new($arg,...)
136
137			The constructor returns some object that encapsulate the state of the
138			message-digest algorithm. You can add data to the object and finally
139			ask for the digest. The "XXX" should of course be replaced by the proper
140			name of the digest algorithm you want to use.
141
142			The two first forms are simply syntactic sugar which automatically
143			load the right module on first use. The second form allow you to use
144			algorithm names which contains letters which are not legal perl
145			identifiers, e.g. "SHA-1". If no implementation for the given algorithm
146			can be found, then an exception is raised.
147
148			If new() is called as an instance method (i.e. $ctx->new) it will just
149			reset the state the object to the state of a newly created object. No
150			new object is created in this case, and the return value is the
151			reference to the object (i.e. $ctx).
152
153			=item $other_ctx = $ctx->clone
154
155			The clone method creates a copy of the digest state object and returns
156			a reference to the copy.
157
158			=item $ctx->reset
159
160			This is just an alias for $ctx->new.
161
162			=item $ctx->add( $data, ... )
163
164			The $data provided as argument are appended to the message we
165			calculate the digest for. The return value is the $ctx object itself.
166
167			=item $ctx->addfile( $io_handle )
168
169			The $io_handle is read until EOF and the content is appended to the
170			message we calculate the digest for. The return value is the $ctx
171			object itself.
172
173			=item $ctx->add_bits( $data, $nbits )
174
175			=item $ctx->add_bits( $bitstring )
176
177			The bits provided are appended to the message we calculate the digest
178			for. The return value is the $ctx object itself.
179
180			The two argument form of add_bits() will add the first $nbits bits
181			from data. For the last potentially partial byte only the high order
182			C<< $nbits % 8 >> bits are used. If $nbits is greater than C<<
183			length($data) * 8 >>, then this method would do the same as C<<
184			$ctx->add($data) >>, i.e. $nbits is silently ignored.
185
186			The one argument form of add_bits() takes a $bitstring of "1" and "0"
187			chars as argument. It's a shorthand for C<< $ctx->add_bits(pack("B*",
188			$bitstring), length($bitstring)) >>.
189
190			This example shows two calls that should have the same effect:
191
192			$ctx->add_bits("111100001010");
193			$ctx->add_bits("\xF0\xA0", 12);
194
195			Most digest algorithms are byte based. For those it is not possible
196			to add bits that are not a multiple of 8, and the add_bits() method
197			will croak if you try.
198
199			=item $ctx->digest
200
201			Return the binary digest for the message.
202
203			Note that the C<digest> operation is effectively a destructive,
204			read-once operation. Once it has been performed, the $ctx object is
205			automatically C<reset> and can be used to calculate another digest
206			value. Call $ctx->clone->digest if you want to calculate the digest
207			without reseting the digest state.
208
209			=item $ctx->hexdigest
210
211			Same as $ctx->digest, but will return the digest in hexadecimal form.
212
213			=item $ctx->b64digest
214
215			Same as $ctx->digest, but will return the digest as a base64 encoded
216			string.
217
218			=back
219
220			=head1 Digest speed
221
222			This table should give some indication on the relative speed of
223			different algorithms. It is sorted by throughput based on a benchmark
224			done with of some implementations of this API:
225
226			Algorithm Size Implementation MB/s
227
228			MD4 128 Digest::MD4 v1.3 165.0
229			MD5 128 Digest::MD5 v2.33 98.8
230			SHA-256 256 Digest::SHA2 v1.1.0 66.7
231			SHA-1 160 Digest::SHA v4.3.1 58.9
232			SHA-1 160 Digest::SHA1 v2.10 48.8
233			SHA-256 256 Digest::SHA v4.3.1 41.3
234			Haval-256 256 Digest::Haval256 v1.0.4 39.8
235			SHA-384 384 Digest::SHA2 v1.1.0 19.6
236			SHA-512 512 Digest::SHA2 v1.1.0 19.3
237			SHA-384 384 Digest::SHA v4.3.1 19.2
238			SHA-512 512 Digest::SHA v4.3.1 19.2
239			Whirlpool 512 Digest::Whirlpool v1.0.2 13.0
240			MD2 128 Digest::MD2 v2.03 9.5
241
242			Adler-32 32 Digest::Adler32 v0.03 1.3
243			CRC-16 16 Digest::CRC v0.05 1.1
244			CRC-32 32 Digest::CRC v0.05 1.1
245			MD5 128 Digest::Perl::MD5 v1.5 1.0
246			CRC-CCITT 16 Digest::CRC v0.05 0.8
247
248			These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running
249			under Linux on a P4 2.8 GHz CPU. The last 5 entries differ by being
250			pure perl implementations of the algorithms, which explains why they
251			are so slow.
252
253			=head1 SEE ALSO
254
255			L<Digest::Adler32>, L<Digest::CRC>, L<Digest::Haval256>,
256			L<Digest::HMAC>, L<Digest::MD2>, L<Digest::MD4>, L<Digest::MD5>,
257			L<Digest::SHA>, L<Digest::SHA1>, L<Digest::SHA2>, L<Digest::Whirlpool>
258
259			New digest implementations should consider subclassing from L<Digest::base>.
260
261			L<MIME::Base64>
262
263			=head1 AUTHOR
264
265			Gisle Aas <gisle@aas.no>
266
267			The C<Digest::> interface is based on the interface originally
268			developed by Neil Winton for his C<MD5> module.
269
270			This library is free software; you can redistribute it and/or
271			modify it under the same terms as Perl itself.
272
273			Copyright 1998-2001,2003-2004 Gisle Aas.
274			Copyright 1995-1996 Neil Winton.
275
276			=cut