On Sat June 6 2009, jaze lee wrote:
> 2009/6/6 Rustam Rakhimov <rusyas...@gmail.com>:
> > So if you are so brave try the example given before.
> > Than you will feel reality.
> may be you are wright, i try , but i can not get the result.
> if a integer with m bits and another integer with n bits, if the
> multiple , there product has m+n bits or m+n-1 bits.
> 248911498900030209107 is a 21 bits number, so i think the p and q both
> are 11 bits number.
> i wrote a small program to find
> #include <openssl/bn.h>
> #include <openssl/bio.h>
> #include <string.h>
>
> int main() {
> BIO *filebio;
> filebio = BIO_new(BIO_s_file());
> BIO_set_fp(filebio, stdout, BIO_NOCLOSE);
> BN_CTX *mybnctx;
> mybnctx = BN_CTX_new();
> BN_CTX_init(mybnctx);
> BIGNUM *myprime;
> BIGNUM *num1, *div, *rem;
> char str1[] = "248911498900030209107";
>
> num1 = BN_new();
> BN_dec2bn(&num1, str1);
> div = BN_new();
> rem = BN_new();
>
> int i;
> for (i = 0; i < 10000; i++){
> /*
> * i don't know how many the prime integer with 34 bits,
> * so i just try,may be it is too naive think like this
> */
> myprime = BN_generate_prime(NULL, 34, 0, NULL, NULL, NULL,
> NULL);
> BN_div(div, rem, num1, myprime, mybnctx);
> if(BN_is_zero(rem)) {
> /* if get it, then print them*/
> BIO_printf(filebio, "%s\n", BN_bn2dec(div));
> BIO_printf(filebio, "%s\n", BN_bn2dec(myprime));
> }
> }
>
> BIO_free(filebio);
> BN_free(num1);
> BN_free(rem);
> BN_free(div);
> BN_free(myprime);
> BN_CTX_free(mybnctx);
>
> }
>
> i still not understand the problem. although i don''t get the result.
>
Now modify your program for a number of cryptographic size, say 4096 bits.
Try again.
Note: There are a lot of big number libraries, some much easier to use.
http://www.walter-fendt.de/m14e/primes.htm
Or ask Google about the subject.
Or cheat a bit, here is a table of the primes upto 9 digits -
A long, long way from 300 digits, but a start. ;)
Notice also in your reading if the term "digits" is used -
If not qualified, it usually means _decimal_ digits not
binary digits (those are usually called "bits").
Mike
>
>
> >
> > -------------------------
> > Best Regards Rustam !!!
> >
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