20060224, 10:14  #1 
3·617 Posts 
Running time for GNFS
Now I am implementing GNFS algorithm in C++.
Anyone please tell me about the runnong time for GNFS algorithm to factor 128 bit numbers in a single machine.Is it possible to factor a 256 bit number using a single machine & how much time it will take for successful factorization? 
20060224, 14:38  #2  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
2·3·13·137 Posts 
Quote:
I could tell you the answers but you will learn much more by following my advice. Ok then  the answers are: a few seconds to a few minutes, depending on your hardware and the efficiency of your code; yes; a few minutes to a few hours, depending on your hardware and the efficiency of your code. Paul 

20060224, 23:32  #3  
Tribal Bullet
Oct 2004
110111010010_{2} Posts 
Quote:
jasonp 

20060227, 07:00  #4  
1100011000101_{2} Posts 
Quote:
Why we are still using 256 bit RSA keys in PGP(email security)?. I think PGP is secured only because of SHA (signature algorithm). Is it correct? Can we replace RSA with ECC?. 

20060227, 14:33  #5  
Tribal Bullet
Oct 2004
2×29×61 Posts 
Quote:
256 bits is a little over 80 digits. Msieve can do factorizations that size in about 2025 minutes, so yes this size is not secure at all. But an RSA modulus is twice the size of its factors, and 512 bit factorizations are still hard. SHA is the Secure Hash Algorithm, and is just a way to crunch arbitrary size messages down to a size where the entire message can be processed at once by whatever public key algorithm your copy of PGP is configured to use. Primarily it's there to prevent duplicate/forged data from being signed; it in no way affects the security of the signature process itself. Maybe you should skim through Schneier's 'Applied Cryptography' if you have cryptographic applications in mind. jasonp Last fiddled with by jasonp on 20060227 at 14:37 

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