ext::Digest::MD5:Perl(Programmers Refereext::Digest::MD5::MD5(3p)NAMEDigest::MD5 - Perl interface to the MD5 Algorithm
SYNOPSIS
# Functional style
use Digest::MD5 qw(md5 md5_hex md5_base64);
$digest = md5($data);
$digest = md5_hex($data);
$digest = md5_base64($data);
# OO style
use Digest::MD5;
$ctx = Digest::MD5->new;
$ctx->add($data);
$ctx->addfile(*FILE);
$digest = $ctx->digest;
$digest = $ctx->hexdigest;
$digest = $ctx->b64digest;
DESCRIPTION
The "Digest::MD5" module allows you to use the RSA Data
Security Inc. MD5 Message Digest algorithm from within Perl
programs. The algorithm takes as input a message of arbi-
trary length and produces as output a 128-bit "fingerprint"
or "message digest" of the input.
Note that the MD5 algorithm is not as strong as it used to
be. It has since 2005 been easy to generate different mes-
sages that produce the same MD5 digest. It still seems hard
to generate messages that produce a given digest, but it is
probably wise to move to stronger algorithms for applica-
tions that depend on the digest to uniquely identify a mes-
sage.
The "Digest::MD5" module provide a procedural interface for
simple use, as well as an object oriented interface that can
handle messages of arbitrary length and which can read files
directly.
FUNCTIONS
The following functions are provided by the "Digest::MD5"
module. None of these functions are exported by default.
md5($data,...)
This function will concatenate all arguments, calculate
the MD5 digest of this "message", and return it in
binary form. The returned string will be 16 bytes long.
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The result of md5("a", "b", "c") will be exactly the
same as the result of md5("abc").
md5_hex($data,...)
Same as md5(), but will return the digest in hexadecimal
form. The length of the returned string will be 32 and
it will only contain characters from this set: '0'..'9'
and 'a'..'f'.
md5_base64($data,...)
Same as md5(), but will return the digest as a base64
encoded string. The length of the returned string will
be 22 and it will only contain characters from this set:
'A'..'Z', 'a'..'z', '0'..'9', '+' and '/'.
Note that the base64 encoded string returned is not pad-
ded to be a multiple of 4 bytes long. If you want
interoperability with other base64 encoded md5 digests
you might want to append the redundant string "==" to
the result.
METHODS
The object oriented interface to "Digest::MD5" is described
in this section. After a "Digest::MD5" object has been
created, you will add data to it and finally ask for the
digest in a suitable format. A single object can be used to
calculate multiple digests.
The following methods are provided:
$md5 = Digest::MD5->new
The constructor returns a new "Digest::MD5" object which
encapsulate the state of the MD5 message-digest algo-
rithm.
If called as an instance method (i.e. $md5->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.
$md5->reset
This is just an alias for $md5->new.
$md5->clone
This a copy of the $md5 object. It is useful when you do
not want to destroy the digests state, but need an
intermediate value of the digest, e.g. when calculating
digests iteratively on a continuous data stream. Exam-
ple:
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my $md5 = Digest::MD5->new;
while (<>) {
$md5->add($_);
print "Line $.: ", $md5->clone->hexdigest, "\n";
}
$md5->add($data,...)
The $data provided as argument are appended to the mes-
sage we calculate the digest for. The return value is
the $md5 object itself.
All these lines will have the same effect on the state
of the $md5 object:
$md5->add("a"); $md5->add("b"); $md5->add("c");
$md5->add("a")->add("b")->add("c");
$md5->add("a", "b", "c");
$md5->add("abc");
$md5->addfile($io_handle)
The $io_handle will be read until EOF and its content
appended to the message we calculate the digest for.
The return value is the $md5 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 $md5 object will be in. The
addfile() method might have been able to read the file
partially before it failed. It is probably wise to dis-
card or reset the $md5 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.
$md5->add_bits($data, $nbits)
$md5->add_bits($bitstring)
Since the MD5 algorithm is byte oriented you might only
add bits as multiples of 8, so you probably want to just
use add() instead. The add_bits() method is provided
for compatibility with other digest implementations.
See Digest for description of the arguments that
add_bits() take.
$md5->digest
Return the binary digest for the message. The returned
string will be 16 bytes long.
Note that the "digest" operation is effectively a des-
tructive, read-once operation. Once it has been per-
formed, the "Digest::MD5" object is automatically
"reset" and can be used to calculate another digest
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value. Call $md5->clone->digest if you want to calcu-
late the digest without resetting the digest state.
$md5->hexdigest
Same as $md5->digest, but will return the digest in hex-
adecimal form. The length of the returned string will be
32 and it will only contain characters from this set:
'0'..'9' and 'a'..'f'.
$md5->b64digest
Same as $md5->digest, but will return the digest as a
base64 encoded string. The length of the returned
string will be 22 and it will only contain characters
from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+' and
'/'.
The base64 encoded string returned is not padded to be a
multiple of 4 bytes long. If you want interoperability
with other base64 encoded md5 digests you might want to
append the string "==" to the result.
EXAMPLES
The simplest way to use this library is to import the
md5_hex() function (or one of its cousins):
use Digest::MD5qw(md5_hex);
print "Digest is ", md5_hex("foobarbaz"), "\n";
The above example would print out the message:
Digest is 6df23dc03f9b54cc38a0fc1483df6e21
The same checksum can also be calculated in OO style:
use Digest::MD5;
$md5 = Digest::MD5->new;
$md5->add('foo', 'bar');
$md5->add('baz');
$digest = $md5->hexdigest;
print "Digest is $digest\n";
With OO style you can break the message arbitrary. This
means that we are no longer limited to have space for the
whole message in memory, i.e. we can handle messages of any
size.
This is useful when calculating checksum for files:
use Digest::MD5;
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my $file = shift || "/etc/passwd";
open(FILE, $file) or die "Can't open '$file': $!";
binmode(FILE);
$md5 = Digest::MD5->new;
while (<FILE>) {
$md5->add($_);
}
close(FILE);
print $md5->b64digest, " $file\n";
Or we can use the addfile method for more efficient reading
of the file:
use Digest::MD5;
my $file = shift || "/etc/passwd";
open(FILE, $file) or die "Can't open '$file': $!";
binmode(FILE);
print Digest::MD5->new->addfile(*FILE)->hexdigest, " $file\n";
Perl 5.8 support Unicode characters in strings. Since the
MD5 algorithm is only defined for strings of bytes, it can
not be used on strings that contains chars with ordinal
number above 255. The MD5 functions and methods will croak
if you try to feed them such input data:
use Digest::MD5qw(md5_hex);
my $str = "abc\x{300}";
print md5_hex($str), "\n"; # croaks
# Wide character in subroutine entry
What you can do is calculate the MD5 checksum of the UTF-8
representation of such strings. This is achieved by filter-
ing the string through encode_utf8() function:
use Digest::MD5qw(md5_hex);
use Encode qw(encode_utf8);
my $str = "abc\x{300}";
print md5_hex(encode_utf8($str)), "\n";
# 8c2d46911f3f5a326455f0ed7a8ed3b3
SEE ALSO
Digest, Digest::MD2, Digest::SHA1, Digest::HMAC
md5sum(1)
RFC 1321
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http://en.wikipedia.org/wiki/MD5
The paper "How to Break MD5 and Other Hash Functions" by
Xiaoyun Wang and Hongbo Yu.
COPYRIGHT
This library is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.
Copyright 1998-2003 Gisle Aas.
Copyright 1995-1996 Neil Winton.
Copyright 1991-1992 RSA Data Security, Inc.
The MD5 algorithm is defined in RFC 1321. This implementa-
tion is derived from the reference C code in RFC 1321 which
is covered by the following copyright statement:
+ Copyright (C) 1991-2, RSA Data Security, Inc. Created
1991. All rights reserved.
License to copy and use this software is granted pro-
vided that it is identified as the "RSA Data Security,
Inc. MD5 Message-Digest Algorithm" in all material men-
tioning or referencing this software or this function.
License is also granted to make and use derivative works
provided that such works are identified as "derived from
the RSA Data Security, Inc. MD5 Message-Digest Algo-
rithm" in all material mentioning or referencing the
derived work.
RSA Data Security, Inc. makes no representations con-
cerning either the merchantability of this software or
the suitability of this software for any particular pur-
pose. It is provided "as is" without express or implied
warranty of any kind.
These notices must be retained in any copies of any part
of this documentation and/or software.
This copyright does not prohibit distribution of any version
of Perl containing this extension under the terms of the GNU
or Artistic licenses.
AUTHORS
The original "MD5" interface was written by Neil Winton
("N.Winton@axion.bt.co.uk").
The "Digest::MD5" module is written by Gisle Aas
<gisle@ActiveState.com>.
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