| Digest::MD5 - Perl interface to the MD5 Algorithm |
Digest::MD5 - Perl interface to the MD5 Algorithm
# 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 = $ctx->b64digest;
The Digest::MD5 module allows you to use the RSA Data Security
Inc. MD5 Message Digest algorithm from within Perl programs. The
algorithm takes as input a message of arbitrary length and produces as
output a 128-bit ``fingerprint'' or ``message digest'' of the input.
Note that the MD5 algorithm is not as strong as it used to be. It has since 2005 been easy to generate different messages that produce the same MD5 digest. It still seems hard to generate messages that produce a given digest, but it is probably wise to move to stronger algorithms for applications that depend on the digest to uniquely identify a message.
The Digest::MD5 module provide a procedural interface for simple
use, as well as an object oriented interface that can handle messages
of arbitrary length and which can read files directly.
The following functions are provided by the Digest::MD5 module.
None of these functions are exported by default.
md5($data,...)The result of md5(``a'', ``b'', ``c'') will be exactly the same as the result of md5(``abc'').
md5_hex($data,...)md5_base64($data,...)Note that 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 redundant string ``=='' to the result.
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:
Digest::MD5 object which encapsulate
the state of the MD5 message-digest algorithm.
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.
my $md5 = Digest::MD5->new;
while (<>) {
$md5->add($_);
print "Line $.: ", $md5->clone->hexdigest, "\n";
}
add($data,...)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");
$md5->add("abc");
addfile($io_handle)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 discard
or reset the $md5 object if this occurs.
In most cases you want to make sure that the $io_handle is in
binmode before you pass it as argument to the addfile() method.
add_bits($bitstring)add() instead. The
add_bits() method is provided for compatibility with other digest
implementations. See the Digest manpage for description of the arguments
that add_bits() take.
Note that the digest operation is effectively a destructive,
read-once operation. Once it has been performed, the Digest::MD5
object is automatically reset and can be used to calculate another
digest value. Call $md5->clone->digest if you want to calculate the
digest without resetting the digest state.
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.
The simplest way to use this library is to import the md5_hex()
function (or one of its cousins):
use Digest::MD5 qw(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;
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::MD5 qw(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 filtering the
string through encode_utf8() function:
use Digest::MD5 qw(md5_hex);
use Encode qw(encode_utf8);
my $str = "abc\x{300}";
print md5_hex(encode_utf8($str)), "\n";
# 8c2d46911f3f5a326455f0ed7a8ed3b3
the Digest manpage, the Digest::MD2 manpage, the Digest::SHA1 manpage, the Digest::HMAC manpage
md5sum(1)
RFC 1321
http://en.wikipedia.org/wiki/MD5
The paper ``How to Break MD5 and Other Hash Functions'' by Xiaoyun Wang and Hongbo Yu.
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 implementation is derived from the reference C code in RFC 1321 which is covered by the following copyright statement:
License to copy and use this software is granted provided that it is identified as the ``RSA Data Security, Inc. MD5 Message-Digest Algorithm'' in all material mentioning 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 Algorithm'' in all material mentioning or referencing the derived work.
RSA Data Security, Inc. makes no representations concerning either the merchantability of this software or the suitability of this software for any particular purpose. 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.
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>.
| Digest::MD5 - Perl interface to the MD5 Algorithm |