Genpassphrase

genpassphrase

This pass phrase generator take clean words from dictionary to build random phrases and compute entropy.

Follow the idea found at: http://xkcd.com/936/

It is a perl script that take a dictionary file, create a uniq cleaned words list (with only flat lower letters from a to z) take randoms words and compute entropy.

Syntaxe:

Usage: passphrase.pl [-h] [-q] [-d dict file] [-s outputfile]
   [-i mIn length] [-a mAx length] [-e entropy bits] [-r random file]
   [-w words] [-l lines] [lines]
Version: passphrase.pl v1.5.1.2 - (2013-07-05 08:51:52).
    -h           This help.
    -l num       number of phrases to generate  (default: 1)
    -w num       number of words by phrase  (default: 5)
    -e bits      Entropy bits for each words (default: 15)
    -d filename  Dictionary file (default: /usr/share/dict/american-english)
    -s filename  Dict file to save after initial drop (default: none)
    -i length    Minimal word length (default: 4)
    -a length    Maximal word length (default: 11)
    -r device    Random file or generator (default: /dev/urandom)
    -q           Quietly generate lines without computations.

Output sample:

$ ./passphrase.pl -l 4
With 5 words over 32768 (     15 entropy bits ) = 1/3.777893e+22 -> 75 bits.
With 5 words from 56947 ( 15.797 entropy bits ) = 1/5.988999e+23 -> 78.987 bits.
  3.634 192.718 airfoils    desolated   babysitting hits        digresses   
  3.391 173.916 acidic      parents     scary       trespassed  fascinate   
  3.704 164.515 occluded    rarely      sweatier    metallic    squat       
  3.907 192.718 available   stockpiling blazoning   jaywalk     chino       

Explanation: There are 56947 word (15.79bits) containing 4 to 11 letters in /usr/share/dict/american-english, after randomly dropped this down to 32768 (round to 15 bits entropy), building lines of 5 random words, compute shannon's entropy and flat entropy, for each lines and printout.

Or simply:

$ ./genpassphrase.pl -q
firmly predeceased titanium slobbered betrayers