glib/girepository/cmph/miller_rabin.c
2023-10-15 17:56:05 +01:00

68 lines
1.2 KiB
C

#include "miller_rabin.h"
static inline cmph_uint64 int_pow(cmph_uint64 a, cmph_uint64 d, cmph_uint64 n)
{
cmph_uint64 a_pow = a;
cmph_uint64 res = 1;
while(d > 0)
{
if((d & 1) == 1)
res =(((cmph_uint64)res) * a_pow) % n;
a_pow = (((cmph_uint64)a_pow) * a_pow) % n;
d /= 2;
};
return res;
};
static inline cmph_uint8 check_witness(cmph_uint64 a_exp_d, cmph_uint64 n, cmph_uint64 s)
{
cmph_uint64 i;
cmph_uint64 a_exp = a_exp_d;
if(a_exp == 1 || a_exp == (n - 1))
return 1;
for(i = 1; i < s; i++)
{
a_exp = (((cmph_uint64)a_exp) * a_exp) % n;
if(a_exp == (n - 1))
return 1;
};
return 0;
};
cmph_uint8 check_primality(cmph_uint64 n)
{
cmph_uint64 a, d, s, a_exp_d;
if((n % 2) == 0)
return 0;
if((n % 3) == 0)
return 0;
if((n % 5) == 0)
return 0;
if((n % 7 ) == 0)
return 0;
//we decompoe the number n - 1 into 2^s*d
s = 0;
d = n - 1;
do
{
s++;
d /= 2;
}while((d % 2) == 0);
a = 2;
a_exp_d = int_pow(a, d, n);
if(check_witness(a_exp_d, n, s) == 0)
return 0;
a = 7;
a_exp_d = int_pow(a, d, n);
if(check_witness(a_exp_d, n, s) == 0)
return 0;
a = 61;
a_exp_d = int_pow(a, d, n);
if(check_witness(a_exp_d, n, s) == 0)
return 0;
return 1;
};