# [RC5] How long would it take?

Bruce Ford b.ford at qut.edu.au
Mon Dec 20 10:31:00 EST 1999

```>k, peoples, I know I'm opening a big can of worms here, but with all this
>discussion of waiting for computing power to get better, the following has
>crossed my mind:  How long will RC5 take anyway, assuming 50% as completion
>(or should 100% be completion?)?
>
>I've gone over this a few times, and alas, this is beyong a young math
>student like myself.  To get a very accurate readout, you'd need to
>calculate in:
>-Current %
>-Total Keyrate
>-Rate of user growth
>-Moore's law, knowing that regardless of our number of users, the keyrate
>will always speed up because of computing power.
>
>Anyone up to the calculations?

Well I used to do it every week, so FWIW.

For those that are interested there are rate graphs with "best fit" growth
rate lines at http://www.distributed.net/statistics/ and with an expanded
vertical scale at http://www.distributed.net/statistics/rc5-64.html.  The
regressions are for data from 2-Mar-1998 and exclude the non-RC5 contests
and various outliers.

It is obvious from the graph that a linear increase in rate best
approximates our growth to date and is probably the best assumption to
make.  I'll do both linear and exponential as it is all on the spreadsheet
I use anyway.

Assuming linear growth at 143.8 Mkeys/s/day:
Keyspace search complete on 29-Sep-2002
50% chance of finding key by 11-Aug-2001
10% chance of finding key by 30-Apr-2000

Assuming exponential growth such that rate doubles every 211 days:
Keyspace search complete on 6-Jun-2001
50% chance of finding key by 21-Dec-2000
10% chance of finding key by 28-Mar-2000

For the 3 months (91 days) prior to CSC starting linear growth was 283.8
Mkeys/s/day
Keyspace search complete on 11-Feb-2002
50% chance of finding key by 9-Apr-2001
10% chance of finding key by 9-Apr-2000

Assuming "Moore's Law" would indicate a time to double of 18 months (548
days):
Keyspace search complete on 29-Apr-2002
50% chance of finding key by 6-Jun-2001
10% chance of finding key by 15-Apr-2000

The "50% chance of finding key" means we will search 50% of the remaining
keyspace by that date.

This is all based on data up to 16-Nov-1999.  These dates would be delayed
a few days by CSC.

Bruce Ford                                      b.ford at qut.edu.au
Projects Coordinator
Teaching and Learning Support Services          Ph: +61 7 3864 1178
Queensland University of Technology

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