Add option to only keep first N chars of each word

[bennofs]

This option is useful together with the special EFF wordlist, where each word has an unique 3-character prefix.

[burdges]

Just curious, are the prefixes nearly uniformly distributed over [a-z][a-z][a-z]?

[bennofs]

I am not quite sure how to measure this.

[bennofs]

The first character already is not randomly distributed:

     2 x
      4 q
     11 y
     12 z
     23 k
     32 i
     32 w
     35 v
     37 h
     38 n
     42 b
     43 j
     46 m
     49 t
     50 o
     51 f
     54 l
     54 u
     61 g
     62 r
     70 p
     77 d
     83 c
     92 e
    110 s
    126 a

[burdges]

Apologies for the derail, it's irrelevant since the entropy only increases for an attacker who does not know you used the wordlist, and the map from wordlist to prefix is bijective. :)