


ext::Digest-MD5::Perl3Programmers Referenext::Digest-MD5::MD5(3p)


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.

       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.

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



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           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";
               }



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       $md5->add($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 resetting the digest
           state.

       $md5->hexdigest
           Same as $md5->digest, but will return the digest in
           hexadecimal form. The length of the returned string



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           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>) {
               $md5->add($_);



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           }
           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::SHA, Digest::HMAC

       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.

COPYRIGHT
       This library is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.




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ext::Digest-MD5::Perl3Programmers Referenext::Digest-MD5::MD5(3p)


        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:

       o   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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