Fermi estimates

Philip Jackson philip.jackson at nordnet.fr
Fri Nov 14 16:01:59 CET 2014

On 14/11/14 03:36, Robert J. Hansen wrote:
> Whoops!
>> so 10**30 years.  The universe is about 10 billion years old, or
>> 10**13 years, so ... our brute-force key cracker takes 10**17 times
>> longer than the age of the universe in order to brute-force a 128-bit
>> key.
> 10 billion is 10**10, so it takes 10**20 times the age of the universe.
> But at some point, who's counting?
>> Admittedly, that energy gets released over 10**13 times the age of
>> the universe...
> 10**20.

Thanks for that (and the previous).... It makes the brain hurt but raises a few
questions in my mind.

Does anything prevent the key breaker getting lucky and cracking it first try?
It seems to me that all discussions on key breaking with their very large
numbers always assume that the last try is THE ONE.

And how does the cracker know he has succeeded ?  Does he have to pause between
each iteration to see if he has 'something good' ?  And in the 10**38 key
attempts, what's the chance of having multiple apparently 'GOOD ONES' ?

Perhaps a double bluff is needed :  send the message in plain text with just a
hint that it might be encrypted ?


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