Ethical Hacking

Learn to find vulnerabilities before the bad guys do! Gain real world hands on hacking experience in our state of the art hacking lab. Course designed and taught by expert instructors with years of penetration testing experience. 12 student maximum in every class. Certification attempt included in every package.
Computer Forensics Training at InfoSec Institute

Gain the in-demand skills of a certified computer examiner, learn to recover trace data left behind by fraud, theft, and cybercrime perpetrators. Discover the source of computer crime and abuse at your organization so that it never happens again. All of our class sizes are guaranteed to be 12 students or less to facilitate one-on-one interaction with one of our expert instructors.




Network Security FullDisclosure
[Top] [All Lists]

Re: [Full-disclosure] Rapid integer factorization = end of RSA?

Subject: Re: [Full-disclosure] Rapid integer factorization = end of RSA?
Date: Thu, 26 Apr 2007 22:19:52 +0200 (CEST)
Hello,

If you have, in fact, come up with a fast method of integer
factorization, the currently unfactored challenges (RSA-704 and above)
would be better proof, no?

no. We're talking about mathemetics, aren't we? So, an example for a
assumption is not a *proof*. Neither are two or three...

Providing the factorization of a particular number (whose factorization is 
considered to be not known by anyone) is definitely a proof that you know 
the factorization of that number and that you had a method for finding it. 
Of course, it doesn't say anything about this method -- whether it is a 
general one or whether you were able to find the factors based on graph of 
temperature at the top of Elbrus :-)

On a more relevant note, let me try to explain the method described by the 
original poster, hopefully in a more readable way:

Take an unknown number N, which we are going to factor. Then, by some 
mysterious process, represent the number N, such that 
(I)   N = A1*B1 + A2*B2 + ... An*Bn
AND
(II)  A1*(N-B1) + A2*(N-B2) + ... + An*(N-Bn) = N*(q-1)
holds.

In the examples provided by the original poster, these numbers were always 
created by taking the usual binary expansion of the number and splitting 
each term into a product Ak*Bk. The problem is that not all (if any) such 
splits produce the desired results. The original poster correcly stated 
that the obvious method for obtaining such a split (if it really exists 
under these conditions) runs in log(N)! steps (that's factorial of log(N), 
not just an exclamation... clearly, this number is greater than N, thus 
rendering this approach worse than trial division). He also claimed to 
have a much faster approach, though.

Naturally, IF this can be done, one can find q-1 (thus also p,q) easily. 
In fact, the "easy" part of the algorithm can be even more simplified. The 
sum A1*(N-B1) + A2*(N-B2) + ... An*(N-Bn) can be rewritten as 
N*(A1+A2+...+An) - (A1*B1 + A2*B2 + ... An*Bn) = N*(A1+A2+...+An - 1) and 
the property (II) tells us that this number is equal to N*(q-1). In other 
words, q = (A1+A2+...An), so -once- we obtain the right sets A,B, finding 
the factorization is nothing but summing up a few numbers.

Now, here are two questions for the original poster:

1) Did I understand your factorization "algorithm" correctly?

2) Could you demonstrate how your algorithm works for the number
    2^32+1, please? I have a quite good reason for asking about this
    particular number.

Peter

-- 
[Name] Peter Kosinar   [Quote] 2B | ~2B = exp(i*PI)   [ICQ] 134813278

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/

<Prev in Thread] Current Thread [Next in Thread>