ulli modPower(ulli n, ulli e, ulli mod){
if (e == 0)
return 1;
else if (e % 2 == 0)
return square(modPower(n,e/2,mod)) % mod;
else
return (modPower(n,e-1,mod) * n) % mod;
}
unsigned int modPower(unsigned int b, unsigned int p, unsigned int m) {
//assumes m is no less than 1
if ( p == 0 )
return 1;
if ( p == 1 )
return (b % m);
return (modPower(b,p/2,m) * modPower(b,p-(p/2),m)) % m;
}
int main (int argc, const char * argv[]) {
unsigned int ans = 1, p = 1, m = 1;
unsigned char * ptr;
if ( argv[1] != 0 )
p = atoi(argv[1]);
if ( argv[2] != 0 )
m = atoi(argv[2]);
ptr = (unsigned char *) argv[3];
printf("Input: to the power of %d, modulo by %d\r\n", p, m);
printf("Message: %s\r\n", ptr);
for ( ; ptr != 0 && *ptr != 0; ptr++) {
ans = modPower(*ptr, p, m);
printf(" '%c' %d \t($%x) ^%d mod %d = %d \t($%x)\r\n", *ptr, *ptr, *ptr, p, m, ans, ans, ans);
}
return 0;
}
