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Module Version: 0.11   Source  

NAME ^

Digest::MD6 - Perl interface to the MD6 Algorithm

VERSION ^

This document describes Digest::MD6 version 0.10

SYNOPSIS ^

  # Functional style
  use Digest::MD6 qw(md6 md6_hex md6_base64);

  $digest = md6($data);
  $digest = md6_hex($data);
  $digest = md6_base64($data);

  # OO style
  use Digest::MD6;

  $ctx = Digest::MD6->new;

  # Or set the hash length explicitly
  $ctx = Digest::MD6->new( 512 );

  $ctx->add($data);
  $ctx->addfile(*FILE);

  $digest = $ctx->digest;
  $digest = $ctx->hexdigest;
  $digest = $ctx->b64digest;

DESCRIPTION ^

The Digest::MD6 module allows you to use the MD6 Message Digest algorithm from within Perl programs. The algorithm takes as input a message of arbitrary length and produces as output a "fingerprint" or "message digest" of the input.

INTERFACE ^

The Digest::MD6 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::MD6 module. None of these functions are exported by default.

The hash size (which defaults to 256 bits, 32 characters) can be set before calling these functions:

  $Digest::MD6::HASH_LENGTH = 512; 

md6($data,...)

This function will concatenate all arguments, calculate the MD6 digest of this " message ", and return it in binary form. The returned string will be 16 bytes long.

The result of md6(" a ", " b ", " c ") will be exactly the same as the result of md6(" abc ").

md6_hex($data,...)

Same as md6(), 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'.

md6_base64($data,...)

Same as md6(), 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 md6 digests you might want to append enough '=' characters to make the length a multiple of 4.

Aliases

As a shorthand for setting the hash length via $Digest::MD6::HASH_LENGTH a number of exportable aliases are available:

  md6_224 md6_224_base64 md6_224_hex
  md6_256 md6_256_base64 md6_256_hex
  md6_384 md6_384_base64 md6_384_hex
  md6_512 md6_512_base64 md6_512_hex

These set the hash length before encoding, so instead of writing:

  {
    local $Digest::MD6::HASH_LENGTH = 512;
    my $hash = md6_hex( $data );
  }

you can just:

  my $hash = md6_512_hex( $data );

METHODS ^

The object oriented interface to Digest::MD6 is described in this section. After a Digest::MD6 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:

$md6 = Digest::MD6->new

The constructor returns a new Digest::MD6 object which encapsulate the state of the MD6 message-digest algorithm.

If called as an instance method (i.e. $md6->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.

The hash size will default to $Digest::MD6::HASH_LENGTH but can be overridden by passing a different value to the constructor:

  my $md6 = Digest::MD6->new( 128 );

$md6->reset

This is just an alias for $md6->new.

$md6->clone

This a copy of the $md6 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 $md6 = Digest::MD6->new;
  while (<>) {
    $md6->add($_);
    print " Line $.: ", $md6->clone->hexdigest, " \n ";
  }

$md6->add($data,...)

The $data provided as argument are appended to the message we calculate the digest for. The return value is the $md6 object itself.

All these lines will have the same effect on the state of the $md6 object:

  $md6->add(" a "); $md6->add(" b "); $md6->add(" c ");
  $md6->add(" a ")->add(" b ")->add(" c ");
  $md6->add(" a ", " b ", " c ");
  $md6->add(" abc ");

$md6->addfile($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 $md6 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 $md6 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 $md6 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.

$md6->add_bits($data, $nbits)

$md6->add_bits($bitstring)

Since the MD6 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.

$md6->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::MD6 object is automatically reset and can be used to calculate another digest value. Call $md6->clone->digest if you want to calculate the digest without resetting the digest state.

$md6->hexdigest

Same as $md6->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'.

$md6->b64digest

Same as $md6->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 md6 digests you might want to append the string " == " to the result.

Digest, Digest::MD2, Digest::MD5, Digest::SHA, Digest::HMAC

http://en.wikipedia.org/wiki/MD6

http://groups.csail.mit.edu/cis/md6/

AUTHOR ^

Andy Armstrong <andy@hexten.net>

LICENCE AND COPYRIGHT ^

Copyright (c) 2009, Andy Armstrong <andy@hexten.net>.

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

Based on Digest::MD5 by Gisle Aas which carries this copyright notice:

  Copyright 1998-2003 Gisle Aas.
  Copyright 1995-1996 Neil Winton.
  Copyright 1991-1992 RSA Data Security, Inc.

The MD6 implementation used is http://groups.csail.mit.edu/cis/md6/code/md6_c_code-2009-04-15.zip which is

  Copyright (c) 2008 Ronald L. Rivest

The MD6 code is licensed under the MIT license.

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