Re: [DES] Criteria for Key Recovery target.

[eli+@gs160.sp.cs.cmu.edu]

Russell Holt writes:
>BTW, does anyone have references to statistical comparisons of key
>searches in "real world" settings? Eg, random starting locations
>versus random keys .. etc..

E(time) with all trial keys distinct: 
        1/N Sigma^N i = N/2 = 2^55.
E(time) for random trials:
        1/N + (N-1)/N (1 + E(time))
        so E(time) = N = 2^56.

Centralized keyspace handling is a clear lose, IMO.  The RC4-40
project had server problems; scaling up by another 2^16 would be
non-trivial.  Then there are problems with malicious searchers,
corrupt servers, flaky networks... all this for a factor of two?
(And, admittedly, the reduction in variance.)

To rain on the parade a bit, what this discussion says to me is that
most applications of DES are safe from net cracking for a few years
yet...

-- 
   Eli Brandt
   eli+@cs.cmu.edu