General brute force attack question

[Daniel Krebs]

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Am 17.06.2015 um 01:45 schrieb Robert J. Hansen:
>> Is this a correct interpretation?
> 
> Pretty close.
> 
>> My understanding of en-/decryption is that there is no
>> indication of progress toward finding a successful key match of a
>> given encryption.
> 
> Not quite.  If you're doing a brute-force attack it's easy to 
> figure out what fraction of the possible number of keys you've 
> tried, and to present that as a progress bar -- when the progress 
> bar is half done, you've searched half the possible keys, and thus 
> there's a 50% chance of finding the key by then.  So yes, it's 
> possible to come up with a pretty good estimate of how long it'll 
> take to brute-force a cipher, and that lets you do things like 
> status bars... it's just that the amount of time is, for any good 
> system, ludicrously big.

I think you can't *really* estimate the time to crack a password, all
you can show is the maximum time it will take to try out all possible
combinations. But when you tried 20% of all possible combinations
there is a chance that the next guess will be right. The /typical
Hollywood progress bar/ allways counts up to 100% (or to 00:00 time)
at least in my memory.
Correct me if I'm wrong.

Sincerely
DK
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