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Old 2010-11-18, 07:48   #1
sinide
 
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Default how long it will take factoring a big number 512b

how long it will take factoring a big number 512bit with modern hardware?
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Old 2010-11-18, 08:41   #2
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Only three days.
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Old 2010-11-18, 09:27   #3
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But, Professor, not everyone has access to TeraGrid!
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Old 2010-11-18, 12:15   #4
sinide
 
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three days how to do that?
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Old 2010-11-18, 14:33   #5
xilman
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Quote:
Originally Posted by sinide View Post
how long it will take factoring a big number 512bit with modern hardware?
Dependent on your resources, the answer is anywhere between days and decades.

So, how much of what modern hardware do you have?

BTW, you still haven't answered the question: which RSA key is it and why do you want the factors? You are rather unlikely to get much useful assistance here until you come clean.


Paul
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Old 2010-11-18, 14:43   #6
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Quote:
Originally Posted by sinide View Post
three days how to do that?
Use the General Number Field Sieve along with multiple, tightly coupled
CPUs.
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Old 2010-11-18, 18:14   #7
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Quote:
Originally Posted by sinide View Post
three days how to do that?
Use sufficiently "modern hardware." This will do.
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Old 2010-11-18, 18:20   #8
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512 bits - that would be 154 decimal digits.

I did a GNFS-factorization of a c153 (so it is one digit smaller than your number) for the cunningham project here (see posts #141, #144, #157 and #159), using one core2duo @ 1.8 GHZ (running 24/7), one core2duo @ 2.0 GHz (NOT running 24/7; it was on approx. 30-40% of the calender time) and a fistfull of CPU-days of a P4 @ 3.4 GHz. This took me approx. 70 calender days.

On an intel i7 (8 threads, running 24/7) I guess this should be doable within approx. a month or maybe a little bit more.

Note: for postprocessing (i.e. matrix step) you will need 2 GB RAM on a 64 bit(!) system. (a 32 bit system will fail because it can't allocate enough memory (see here, discussion about the problem and it's solution continued in this thread.))

Last fiddled with by Andi47 on 2010-11-18 at 18:31 Reason: Typo
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Old 2010-11-19, 08:03   #9
sinide
 
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i use ggnfs to do that, my pc is E8400 3GHz,2G RAM.
in the lattice sieving step,i use 3PCs,now i have run 7 days
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