## Re: Big ECM factor!

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• ... ... the prime factors is ... Yes, you re absolutely right. And I m very puzzled as to what caused facter.exe to generate an extraneous factor, how
Message 1 of 8 , Sep 17, 2004
--- In primenumbers@yahoogroups.com, "Jens Kruse Andersen"
<jens.k.a@g...> wrote:
> Jay Berg wrote:
>
<snip>
>
> Something went very wrong with your factor.exe.
> The original number only had 82 digits and the product of
the "prime factors" is
> far greater.
> 101, 68389 and the final 76-digit number are not factors.

> They are actually the factors of 10^82+1.
> The other numbers are all the factors of the original number.
>
> --
> Jens Kruse Andersen

Yes, you're absolutely right. And I'm very puzzled as to what caused
facter.exe to generate an extraneous factor, how it produced an
actual real factor of a real factor of another (10^82+1) N, and why I
didn't notice such a small detail yesterday!

I suppose it comes from using the tools for so long and coming to
trust them too much!

Thank you Jens
• ... Don t blame factor.exe. David Broadhurst has almost certainly solved the mystery. He suggests the 82-digit number must have been pasted twice to
Message 2 of 8 , Sep 17, 2004
Jay Berg wrote:

> And I'm very puzzled as to what caused
> facter.exe to generate an extraneous factor, how it produced an
> actual real factor of a real factor of another (10^82+1) N

Don't blame factor.exe.
David Broadhurst has almost certainly solved the mystery. He suggests the
82-digit number must have been pasted twice to factor.exe, i.e. multiplied by
10^82+1.

Why didn't I think of that?
Probably because I'm not a nuclear physicist.

--
Jens Kruse Andersen
• ... suggests the ... multiplied by ... That solves it and allows me to recreate the results! Thanks for helping resolve the problem. I d much rather it be my
Message 3 of 8 , Sep 17, 2004
--- In primenumbers@yahoogroups.com, "Jens Kruse Andersen"
<jens.k.a@g...> wrote:
> Jay Berg wrote:
>
> > And I'm very puzzled as to what caused
> > facter.exe to generate an extraneous factor, how it produced an
> > actual real factor of a real factor of another (10^82+1) N
>
> Don't blame factor.exe.
> David Broadhurst has almost certainly solved the mystery. He
suggests the
> 82-digit number must have been pasted twice to factor.exe, i.e.
multiplied by
> 10^82+1.

That solves it and allows me to recreate the results! Thanks for
helping resolve the problem.

I'd much rather it be my sloppy cut 'n pasting, than to be wondering
about a tool that has proven so valuable. Now that I know it was my
booboo, I can stop wondering.

Thanks again for helping to point out the error AND helping to
resolve the cause.

Jay
• Is factor.exe open source? Rob ... From: Jens Kruse Andersen [mailto:jens.k.a@get2net.dk] Sent: Friday, September 17, 2004 4:15 AM To:
Message 4 of 8 , Sep 17, 2004
Is factor.exe open source?

Rob

-----Original Message-----
From: Jens Kruse Andersen [mailto:jens.k.a@...]
Sent: Friday, September 17, 2004 4:15 AM
Subject: Re: [PrimeNumbers] Big ECM factor!

Jay Berg wrote:

> Anyway, sure enough, out popped a big factor.
> 3518005926601707472344309601987042658861560810593957361511478230105755
> 939320279041

> first trying brute force division by small primes
> PRIME FACTOR 101
> PRIME FACTOR 257
> PRIME FACTOR 641
> now trying 1000 iterations of brent's method
> PRIME FACTOR 68389
> PRIME FACTOR 114689
> PRIME FACTOR 274177
> PRIME FACTOR 65537
> PRIME FACTOR 974849
> PRIME FACTOR 2424833
> PRIME FACTOR 319489
> PRIME FACTOR 6700417
> PRIME FACTOR 26017793
> PRIME FACTOR 63766529
> PRIME FACTOR 6487031809
> now trying william's (p+1) method
> phase 1 - trying all primes less than 10000
> phase 2 - trying last prime less than 1000000
> PRIME FACTOR 190274191361
> PRIME FACTOR
> 1447745997018511893740076606031686237538345362413531560645573104006506
> 749609

Something went very wrong with your factor.exe.
The original number only had 82 digits and the product of the "prime
factors" is
far greater.
101, 68389 and the final 76-digit number are not factors.
They are actually the factors of 10^82+1.
The other numbers are all the factors of the original number.

--
Jens Kruse Andersen

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• ... There s several versions of it floating around. I d suggest you start the search for a good source base at the following URL.
Message 5 of 8 , Sep 17, 2004
--- In primenumbers@yahoogroups.com, "Robert Sitton \(old\)"
<rsitton@a...> wrote:
> Is factor.exe open source?

There's several versions of it floating around. I'd suggest you start
the search for a good source base at the following URL.

http://home.netcom.com/~jrhowell/math/software.htm

It's a very good tool for cracking most composites. Of course it
doesn't work on the "most desired". However it is very good on
breaking apart composite factors generated by other tools.
• The tool in question is part of the Miracl big number library (at least that is what the output text looks like). Miracl can be downloaded from:
Message 6 of 8 , Sep 17, 2004
The "tool" in question is part of the Miracl big number library
(at least that is what the output text looks like). Miracl

http://indigo.ie/~mscott

--- In primenumbers@yahoogroups.com, "Jay Berg" <jberg@e...> wrote:
> --- In primenumbers@yahoogroups.com, "Robert Sitton \(old\)"
> <rsitton@a...> wrote:
> > Is factor.exe open source?
>
> There's several versions of it floating around. I'd suggest you
start
> the search for a good source base at the following URL.
>
> http://home.netcom.com/~jrhowell/math/software.htm
>
> It's a very good tool for cracking most composites. Of course it
> doesn't work on the "most desired". However it is very good on
> breaking apart composite factors generated by other tools.
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