20091029, 06:50  #1 
Oct 2009
3^{2}·7 Posts 
A strange RSA key
Finally С154 job is done:
78M relations collected, from 0 to 35M 39M Unique relations Three prp found, prp24,prp96,prp34 It tooks about a week totally. 1 np 4 days sieving 4 Dual Xeons 1 day matrix solving 12 hours square Last fiddled with by siew on 20091029 at 07:27 
20091029, 08:06  #2  
Nov 2008
2·3^{3}·43 Posts 
Quote:
If it isn't a proper RSA key, you must do ECM first. Then you would have probably found the p24 in 12 minutes, and the p34 in 12 hours. 

20091029, 08:07  #3 
Feb 2005
The Netherlands
11011010_{2} Posts 
prp24 and prp34? Didn't you do some ECM before sieving? Could have save you about a week...
Last fiddled with by BigBrother on 20091029 at 08:07 
20091029, 08:09  #4 
Jul 2006
Calgary
5^{2}×17 Posts 
Do you think the key generator might have somehow mistakenly considered p24 times p34 as a probable prime?

20091029, 08:13  #5  
Nov 2008
4422_{8} Posts 
Quote:
Earlier in the thread, siew wrote: Quote:
Actually, I'm surprised I didn't catch that as a lie early on: if it is a real RSA key used for signing real code, then it has to be better than 512 bits nowadays. Last fiddled with by 10metreh on 20091029 at 08:14 

20091029, 08:48  #6 
Oct 2009
3^{2}·7 Posts 
Please, that was my first big factorization, so what do you mean "ECM before"?

20091029, 09:01  #7 
Jul 2006
Calgary
5^{2}×17 Posts 

20091029, 09:37  #8 
(loop (#_fork))
Feb 2006
Cambridge, England
7·911 Posts 
The problem is that, if you know the key is an RSA number, 'ECM before' is extremely bad advice; it's absolutely guaranteed to waste time.
The crucial question: does the private key you obtain from the factorisation allow you to sign code that works? If so then the encryption system is very peculiar; if not, then maybe the number's in the wrong byte order or has an implicit leading bit or something? 
20091029, 12:08  #9 
Tribal Bullet
Oct 2004
2·3·19·31 Posts 
fivemack is right, the most likely explanation is that the string of bits you think is an RSA key needs to be byteswapped or something.

20091029, 12:15  #10 
Oct 2004
Austria
2·17·73 Posts 
Hmmm... maybe one should spend a few hours (not more!) of ECM and P1 even on RSA keys to see if things like that have happened?

20091029, 13:19  #11 
Oct 2009
3^{2}·7 Posts 
Will try to ECM too :) tanx.
And what about 3 prp ? It it possible , that original key generator used 3 primes, not 2 ? p,q ? 
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