# [rc5] We may only need 5 years...

Seth Dillingham seth at snet.net
Thu Oct 23 17:10:28 EDT 1997

```Eric Gindrup (gindrup at okway.okstate.edu), on 10/23/1997 4:51 PM, wrote
the following:

>     By eyeball at http://home.pacbell.net/cwax/bovineg.html, the Bovine
>     effort seems to double its number of completed keys count every 2.5
>     weeks.  Current keyrate is 5Gkps.
>     Let's say:
>     1.  We start RC5-64 right now.
>     2.  The doubling rate is constant for the duration I'm about to
>     compute.
>     3.  We have to exhaust all of the RC5-64 keyspace.
>
>     Let f(w) be the number of completed keys with w in weeks.  (The
>     following keeps about one significant digit.)
>     f'(0) = 5Gkps.  f(w+2.5) = 2*f(w).  These together mean f(w) =
>     1.4*2^(w/2.5).  To make this =2^64, w=160.
>
>     So, in 3 years, we could exhaust the keyspace.  We'd "probably" find
>     the key in about 18 months.  This is so terrible?
>             -- Eric Gindrup ! gindrup at okway.okstate.edu

And what exactly is the likelihood we could keep that doubling rate up
for that long?

Hah! Yeah right!

Seth Dillingham

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