home *** CD-ROM | disk | FTP | other *** search
- package Digest;
-
- use strict;
- use vars qw($VERSION %MMAP $AUTOLOAD);
-
- $VERSION = "1.15";
-
- %MMAP = (
- "SHA-1" => ["Digest::SHA1", ["Digest::SHA", 1], ["Digest::SHA2", 1]],
- "SHA-224" => [["Digest::SHA", 224]],
- "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, that is 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.
-
- Note that the properties of the algorithms change over time, as the
- algorithms are analyzed and machines grow faster. If your application
- for instance depends on it being "impossible" to generate the same
- digest for a different message it is wise to make it easy to plug in
- stronger algorithms as the one used grow weaker. Using the interface
- documented here should make it easy to change algorithms later.
-
- 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 )
-
- =item $ctx->add( $chunk1, $chunk2, ... )
-
- The string value of the $data provided as argument is appended to the
- message we calculate the digest for. The return value is the $ctx
- object itself.
-
- If more arguments are provided then they are all appended to the
- message, thus all these lines will have the same effect on the state
- of the $ctx object:
-
- $ctx->add("a"); $ctx->add("b"); $ctx->add("c");
- $ctx->add("a")->add("b")->add("c");
- $ctx->add("a", "b", "c");
- $ctx->add("abc");
-
- Most algorithms are only defined for strings of bytes and this method
- might therefore croak if the provided arguments contain chars with
- ordinal number above 255.
-
- =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.
-
- The addfile() method will croak() if it fails reading data for some
- reason. If it croaks it is unpredictable what the state of the $ctx
- object will be in. The addfile() method might have been able to read
- the file partially before it failed. It is probably wise to discard
- or reset the $ctx object if this occurs.
-
- In most cases you want to make sure that the $io_handle is in
- "binmode" before you pass it as argument to the addfile() method.
-
- =item $ctx->add_bits( $data, $nbits )
-
- =item $ctx->add_bits( $bitstring )
-
- The add_bits() method is an alternative to add() that allow partial
- bytes to be appended to the message. Most users should just ignore
- this method as partial bytes is very unlikely to be of any practical
- use.
-
- 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) >>.
-
- 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)) >>.
-
- The return value is the $ctx object itself.
-
- 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 and for these 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 resetting 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>
-
- http://en.wikipedia.org/wiki/Cryptographic_hash_function
-
- =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 1998-2006 Gisle Aas.
- Copyright 1995,1996 Neil Winton.
-
- =cut
-