[RC5] RC5-64 HAS BEEN SOLVED

Marcin Sochacki wanted at panda.bg.univ.gda.pl
Fri Sep 27 17:28:11 EDT 2002


On Fri, Sep 27, 2002 at 03:49:14PM +0200, Richard Menedetter wrote:
>  KW> Kind of nifty though its been solved. Wonder how long RC5-72 will
>  KW> take? 8 yrs?
> Hmmm rc5-72 is 256 [2^(72-64)] times harder then rc5-64.
> 
> We needed nearly 5 years for rc5-64.
> If time needed decreases by a factor of 5 we would need 256 years to solve it.
> 
> This is not an exact calculation :) but it shows that IMHO trying it is ...
> not very wise (and that computing power should be used in other ways ...
> maybe a dnetc protein folding project)
> 
> I really don't see what breaking rc5-72 would gain the world ...
> but the installed dnet-client-base could work on more usefull projects.

I agree with you, that attacing RC5-72 is not a very exciting project,
but your calculation is wrong.

If we started RC5-64 today, we would break it in approximately one year.
Computing power roughly doubles every year. So, the calculation
looks like this:
- this year we count 1/256th part of RC5-72 keyspace,
- next year we count 1/128th part, because our power doubled,
etc.

So, if all goes well we would need 8 years, only :)
It's still too long, and I would really love to hear about a new,
interesting, non-OGR, non-RC5 project from D.Net.

Marcin
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