NAME

       Crypt::GeneratePassword - generate secure random pronounceable passwords

SYNOPSIS

         use Crypt::GeneratePassword qw(word chars);
         $word = word($minlen,$maxlen);
         $word = chars($minlen,$maxlen);
         *Crypt::GeneratePassword::restrict = \&my_restriction_filter;
         *Crypt::GeneratePassword::random_number = \&my_random_number_generator;

DESCRIPTION

       Crypt::GeneratePassword generates random passwords that are (more or less) pronounceable. Unlike
       Crypt::RandPasswd, it doesn't use the FIPS-181 NIST standard, which is proven to be insecure. It does use
       a similar interface, so it should be a drop-in replacement in most cases.

       If you want to use passwords from a different language than english, you can use one of the packaged
       alternate unit tables or generate your own. See below for details.

       For details on why FIPS-181 is insecure and why the solution used in this module is reasonably secure,
       see "A New Attack on Random Pronounceable Password Generators" by Ravi Ganesan and Chris Davies,
       available online in may places - use your favourite search engine.

       This module improves on FIPS-181 using a true random selection with the word generator as mere filter.
       Other improvements are better pronounceability using third order approximation instead of second order
       and multi-language support.  Drawback of this method is that it is usually slower. Then again, computer
       speed has improved a little since 1977.

Functions

   chars
         $word = chars($minlen, $maxlen [, $set [, $characters, $maxcount ] ... ] );

       Generatess a completely random word between $minlen and $maxlen in length.  If $set is given, it must be
       an array ref of characters to use. You can restrict occurrence of some characters by providing
       ($characters, $maxcount) pairs, as many as you like. $characters must be a string consisting of those
       characters which may appear at most $maxcount times in the word.

       Note that the length is determined via relative probability, not uniformly.

   word
         $word = word($minlen, $maxlen [, $lang [, $signs [, $caps [, $minfreq, $avgfreq ] ] ] );
         $word = word3($minlen, $maxlen [, $lang [, $signs [, $caps [, $minfreq, $avgfreq ] ] ] );

       Generates a random pronounceable word. The length of the returned word will be between $minlen and
       $maxlen. If you supply a non-zero value for $numbers, up to that many numbers and special characters will
       occur in the password. If you specify a non-zero value for $caps, up to this many characters will be
       upper case. $lang is the language description to use, loaded via load_language or built-in. Built-in
       languages are: 'en' (english) and 'de' (german). Contributions welcome. The default language is 'en' but
       may be changed by calling load_language with a true value as third parameter. Pass undef as language to
       select the current default language. $minfreq and $minsum determine quality of the password: $minfreq and
       $avgfreq are the minimum frequency each quad/trigram must have and the average frequency that the
       quad/trigrams must have for a word to be selected. Both are values between 0.0 and 1.0, specifying the
       percentage of the maximum frequency. Higher values create less secure, better pronounceable passwords and
       are slower.  Useful $minfreq values are usually between 0.001 and 0.0001, useful $avgfreq values are
       around 0.05 for trigrams (word3) and 0.001 for quadgrams (word).

   analyze
         $ratio = analyze($count,@word_params);
         $ratio = analyze3($count,@word_params);

       Returns a statistical(!) security ratio to measure password quality. $ratio is the ratio of passwords
       chosen among all possible ones, e.g. a ratio of 0.0149 means 1.49% of the theoretical password space was
       actually considered a pronounceable password. Since this analysis is only statistical, it proves
       absolutely nothing if you are deeply concerned about security - but in that case you should use chars(),
       not word() anyways. In reality, it says a lot about your chosen parameters if you use large values for
       $count.

   generate_language
         $language_description = generate_language($wordlist);

       Generates a language description which can be saved in a file and/or loaded with load_language. $wordlist
       can be a string containing whitespace separated words, an array ref containing one word per element or a
       file handle or name to read words from, one word per line7.  Alternatively, you may pass an array
       directly, not as reference.  A language description is about 1MB in size.

       If you generate a general-purpose language description for a language not yet built-in, feel free to
       contribute it for inclusion into this package.

   load_language
         load_language($language_description, $name [, $default]);

       Loads a language description which is then available in words().  $language_desription is a string
       returned by generate_language, $name is a name of your choice which is used to select this language as
       the fifth parameter of words(). You should use the well-known ISO two letter language codes if possible,
       for best interoperability.

       If you specify $default with a true value, this language will be made global default language. If you
       give undef as $language_description, only the default language will be changed.

   random_number
         $number = random_number($limit);

       Returns a random integer between 0 (inclusive) and $limit (exclusive).  Change this to a function of your
       choice by doing something like this:

           {
             local $^W; # squelch sub redef warning.
             *Crypt::GeneratePassword::random_number = \&my_rng;
           }

       The default implementation uses perl's rand(), which might not be appropriate for some sites.

   restrict
         $forbidden = restrict($word,$language);

       Filters undesirable words. Returns false if the $word is allowed in language $lang, false otherwise.
       Change this to a function of your choice by doing something like this:

           {
             local $^W; # squelch sub redef warning.
             *Crypt::GeneratePassword::restrict = \&my_filter;
           }

       The default implementation scans for a few letter sequences that english or german people might find
       offending, mostly because of their sexual nature. You might want to hook up a regular password checker
       here, or a wordlist comparison.

VERSION

       This document describes version 0.03

AUTHOR

       Copyright 2002 by Joerg Walter <jwalt@cpan.org>, inspired by ideas from Tom Van Vleck and Morris
       Gasser/FIPS-181.

COPYRIGHT

       This perl module is free software; it may be redistributed and/or modified under the same terms as Perl
       itself.

SEE ALSO

       Crypt::RandPasswd.

perl v5.10.0                                       2003-09-09                       Crypt::GeneratePassword(3pm)