[RC5] RC5-72: status request

Décio Luiz Gazzoni Filho decio at decpp.net
Mon Aug 11 18:19:29 EDT 2008


On Aug 11, 2008, at 6:14 PM, bert wrote:

> Ed Wensell III wrote:
>> --- On Mon, 8/11/08, bert <bertodell at suddenlink.net> wrote:
>>
>>
>>> I bet they are wanting
>>> the OGR people to
>>> do RC5-72 since it will take more than a 1000  years to
>>> complete(despite
>>> what loyalists will say,RC5-72 hasn't hit 1% and
>>> won't for probably
>>> another 5 1/2 years and probably another 100 years after
>>> that before it
>>> hits 10% lol)
>>>
>>> Bert O'Dell
>>> _______________________________________________
>>> rc5 mailing list
>>> rc5 at lists.distributed.net
>>> http://lists.distributed.net/mailman/listinfo/rc5
>>>
>>
>> Unless we can get our hands on 1 million PS3's, at which point  
>> it'll be done in a year (there have been 14.4 million units sold as  
>> of June 2008, 5 million of those are in the US).
>>
>> --
>> Ed Wensell III
>>
>> 24/7 support is only available for 3.428571 hours per day.
>>
>>
>>
>>
>> _______________________________________________
>> rc5 mailing list
>> rc5 at lists.distributed.net
>> http://lists.distributed.net/mailman/listinfo/rc5
>> ------------------------------------------------------------------------
>>
>>
>> Internal Virus Database is out of date.
>> Checked by AVG.
>> Version: 8.0.100 / Virus Database: 270.4.4/1531 - Release Date:  
>> 7/2/2008 7:02 PM
>>
> Why state something that will never happen and more than likely if
> true(getting a million PS3's),you still won't be making that much of a
> dent in it. It's not going to happen.

Erm... a PS3 can do ~170 Mkeys/s, so 1 million PS3s can do 170 Tkeys/s  
(170*10^12 keys/s). The full keyspace of RC5-72 is 4.72 zettakeys  
(4.72*10^21 keys). If you divide the latter by the former, you get  
23.6 million seconds; a year has 31 million seconds, give or take. So  
worst case, even if we had to search the full keyspace, it would take  
9 months or so; since we expect to search only half the keyspace, make  
that 4.5 months.

We could still meet the 1-year deadline with 400k PS3s, however  
unreasonable that may still seem.

Décio


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