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Digest::MD5(3)
NAME
Digest::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 = $ctx->b64digest;
DESCRIPTION
The "Digest::MD5" module allows you to use the RSA Data Security Inc. MD5
Message Digest algorithm from within Perl programs. The algorithm takes as
input a message of arbitrary length and produces as output a 128-bit
"fingerprint" or "message digest" of the input.
The "Digest::MD5" module provide a procedural interface for simple use, as
well as an object oriented interface that can handle messages of arbitrary
length and which can read files directly.
FUNCTIONS
The following functions are provided by the "Digest::MD5" module. None of
these functions are exported by default.
md5($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.
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 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.
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 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.
$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. Example:
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 message 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 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.
$md5->add_bits($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 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 reseting the digest state.
$md5->hexdigest
Same as $md5->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'.
$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::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
SEE ALSO
Digest, Digest::MD2, Digest::SHA1, Digest::HMAC
md5sum(1)
RFC 1321
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 implementation 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 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.
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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