NAME¶
Digest::MD4 - Perl interface to the MD4 Algorithm
SYNOPSIS¶
# Functional style
use Digest::MD4 qw(md4 md4_hex md4_base64);
$digest = md4($data);
$digest = md4_hex($data);
$digest = md4_base64($data);
# OO style
use Digest::MD4;
$ctx = Digest::MD4->new;
$ctx->add($data);
$ctx->addfile(*FILE);
$digest = $ctx->digest;
$digest = $ctx->hexdigest;
$digest = $ctx->b64digest;
DESCRIPTION¶
The "Digest::MD4" module allows you to use the RSA Data Security Inc.
MD4 Message Digest algorithm from within Perl programs. The algorithm takes as
input a message of arbitrary length and produces as output a 128-bit
"fingerprint" or "message digest" of the input.
The "Digest::MD4" module provide a procedural interface for simple
use, as well as an object oriented interface that can handle messages of
arbitrary length and which can read files directly.
FUNCTIONS¶
The following functions are provided by the "Digest::MD4" module. None
of these functions are exported by default.
- md4($data,...)
- This function will concatenate all arguments, calculate the MD4 digest of
this "message", and return it in binary form. The returned
string will be 16 bytes long.
The result of md4("a", "b", "c") will be
exactly the same as the result of md4("abc").
- md4_hex($data,...)
- Same as md4(), but will return the digest in hexadecimal form. The
length of the returned string will be 32 and it will only contain
characters from this set: '0'..'9' and 'a'..'f'.
- md4_base64($data,...)
- Same as md4(), 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 padded to be a multiple
of 4 bytes long. If you want interoperability with other base64 encoded
md4 digests you might want to append the redundant string "=="
to the result.
METHODS¶
The object oriented interface to "Digest::MD4" is described in this
section. After a "Digest::MD4" 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:
- $md4 = Digest::MD4->new
- The constructor returns a new "Digest::MD4" object which
encapsulate the state of the MD4 message-digest algorithm.
If called as an instance method (i.e. $md4->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.
- $md4->reset
- This is just an alias for $md4->new.
- $md4->clone
- This a copy of the $md4 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.
Example:
my $md4 = Digest::MD4->new;
while (<>) {
$md4->add($_);
print "Line $.: ", $md4->clone->hexdigest, "\n";
}
- $md4->add($data,...)
- The $data provided as argument are appended to the message we calculate
the digest for. The return value is the $md4 object itself.
All these lines will have the same effect on the state of the $md4 object:
$md4->add("a"); $md4->add("b"); $md4->add("c");
$md4->add("a")->add("b")->add("c");
$md4->add("a", "b", "c");
$md4->add("abc");
- $md4->addfile($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 $md4 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 $md4
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 $md4 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.
- $md4->digest
- Return the binary digest for the message. The returned string will be 16
bytes long.
Note that the "digest" operation is effectively a destructive,
read-once operation. Once it has been performed, the
"Digest::MD4" object is automatically "reset" and can
be used to calculate another digest value. Call $md4->clone->digest
if you want to calculate the digest without reseting the digest
state.
- $md4->hexdigest
- Same as $md4->digest, 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'.
- $md4->b64digest
- Same as $md4->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 md4 digests
you might want to append the string "==" to the result.
EXAMPLES¶
The simplest way to use this library is to import the
md4_hex() function
(or one of its cousins):
use Digest::MD4 qw(md4_hex);
print "Digest is ", md4_hex("foobarbaz"), "\n";
The above example would print out the message:
Digest is b2b2b528f632f554ae9cb2c02c904eeb
The same checksum can also be calculated in OO style:
use Digest::MD4;
$md4 = Digest::MD4->new;
$md4->add('foo', 'bar');
$md4->add('baz');
$digest = $md4->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::MD4;
my $file = shift || "/etc/passwd";
open(FILE, $file) or die "Can't open '$file': $!";
binmode(FILE);
$md4 = Digest::MD4->new;
while (<FILE>) {
$md4->add($_);
}
close(FILE);
print $md4->b64digest, " $file\n";
Or we can use the addfile method for more efficient reading of the file:
use Digest::MD4;
my $file = shift || "/etc/passwd";
open(FILE, $file) or die "Can't open '$file': $!";
binmode(FILE);
print Digest::MD4->new->addfile(*FILE)->hexdigest, " $file\n";
Perl 5.8 support Unicode characters in strings. Since the MD4 algorithm is only
defined for strings of bytes, it can not be used on strings that contains
chars with ordinal number above 255. The MD4 functions and methods will croak
if you try to feed them such input data:
use Digest::MD4 qw(md4_hex);
my $str = "abc\x{300}";
print md4_hex($str), "\n"; # croaks
# Wide character in subroutine entry
What you can do is calculate the MD4 checksum of the UTF-8 representation of
such strings. This is achieved by filtering the string through
encode_utf8() function:
use Digest::MD4 qw(md4_hex);
use Encode qw(encode_utf8);
my $str = "abc\x{300}";
print md4_hex(encode_utf8($str)), "\n";
# fc2ef2836f9bc3f44ed6d7adee2f1533
SEE ALSO¶
Digest, Digest::MD2, Digest::SHA1, Digest::HMAC
md4sum(1)
RFC 1320
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 MD4 algorithm is defined in RFC 1320. This implementation is derived from
the reference C code in RFC 1320 which is covered by the following copyright
statement:
- •
-
Copyright (C) 1990-2, RSA Data Security, Inc. All rights reserved.
License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD4 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. MD4 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.
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>.
The "Digest::MD4" module is derived from Digest::MD5 by Mike McCauley
(mikem@airspayce.com)