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Groups > comp.lang.forth > #26480

Re: random password generator

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Bernd Paysan <bernd.paysan@gmx.de> writes:
> This is a script.  Things you just need to do once (e.g. open /dev/random) 
> don't need to go into a definition.  Just do them in interactive mode.

Thanks!  Hmm, ok, I thought it was easier to debug and test stuff by
putting all the code into definitions, though in a very simple script
like this it probably doesn't matter much.

> Use throw on iors.  

Thanks, that's useful.  I just found the info in the exceptions chapter
of the gforth manual.  That took a little searching because throw isn't
in the word index (maybe you could add it):

http://www.complang.tuwien.ac.at/forth/gforth/Docs-html/Word-Index.html

> If you have questions whether your alphabet really is 64 characters,
> add a ~~ right after the string once for debugging.

Yeah the assert was kind of a built-in unit test.  I generally prefer to
leave things like that in programs if I don't mind the tiny bit of
bloat.  It's mostly to catch if I make a mistake in a later
modification, rather than to check that the code works in the first
place.

> Here's how I would do it:
>
> #! /usr/bin/gforth
>
> s" /dev/urandom" r/o open-file throw value rndfd
> : randombyte ( -- c )  rndfd key-file ;
> : >alphabet ( n -- c )  $3F and
>   s" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_="
>   drop + c@ ;
> : passwd ( len -- )  0 ?DO  randombyte >alphabet emit  LOOP cr ;
>
> 12 passwd bye

That is nice!  I didn't know about key-file either.

> : >alphabet ( u16 -- c )
>   s" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_="
>   rot * 16 rshift + c@ ;

Don't you mean

 : >alphabet ( u16 -- c )
   s" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_="
   rot swap mod + c@ ;

I considered something like that but I figured that the 6-bit alphabet
(or even a 5-bit one) was more in the spirit of Forth minimalism.

I haven't seen any recent systems that don't allow mixed case passwords
but some obnoxious ones -require- the presence of both cases and digits
(that's why I used 6 bits instead of 5).  I decided that most passwords
from this script have that because of their length, and I could just run
the script several times if necessary.

> BTW: Test what you have written, word by word.  Your chk does not work, 
> because "dup =" is always true.

Yes, result of a last-minute refactoring :(.  I posted a correction.

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random password generator Paul Rubin <no.email@nospam.invalid> - 2013-10-12 19:07 -0700
  Re: random password generator hughaguilar96@yahoo.com - 2013-10-12 22:01 -0700
  Re: random password generator Paul Rubin <no.email@nospam.invalid> - 2013-10-12 22:32 -0700
    Re: random password generator hughaguilar96@yahoo.com - 2013-10-12 22:44 -0700
  Re: random password generator "WJ" <w_a_x_man@yahoo.com> - 2013-10-13 08:23 +0000
    Re: random password generator Paul Rubin <no.email@nospam.invalid> - 2013-10-13 05:46 -0700
    Re: random password generator "WJ" <w_a_x_man@yahoo.com> - 2013-10-13 17:09 +0000
  Re: random password generator Bernd Paysan <bernd.paysan@gmx.de> - 2013-10-13 20:32 +0200
    Re: random password generator Paul Rubin <no.email@nospam.invalid> - 2013-10-13 12:27 -0700
      Re: random password generator Bernd Paysan <bernd.paysan@gmx.de> - 2013-10-13 22:52 +0200
        Re: random password generator Paul Rubin <no.email@nospam.invalid> - 2013-10-13 14:43 -0700

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