[Q] Diceware password size

[Denis McCauley]

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On Mon, 26 May 2003 17:40:52 -0400
Daniel Carrera <dcarrera@math.umd.edu> wrote:
> 
> I'd like some help figuring out the security of a diceware passphrase.
> 
>  The diceware word list contains 7776 words.
>  => There are (7776)^5 possible 5-word passphrases.
>  => There is a probability 'p' that the passphrase will be discovered
>     within the first  p*(7776)^5 trials.
> 
>   If I knew the number of trials 'n' that can be performed each minute I 
>   could estimate the security of a diceware passphrase.  Of course, the 
>   value of 'n' depends on the attacker.
> 
In reality it's not that simple, I think. 

First, an attacker must know that Diceware was used. Otherwise he would
try a dictionary attack with a much large word base.

Second, there are two Diceware word lists (in English), which would mean
combining the two and having more than 7776 possibilities.

Third, you can include spaces between the words, or not, which would
double the search time.

Cheers,
- --
=====================================
Denis McCauley
GPG/PGP keys at http://www.djmccauley.tk
=====================================

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