BigUnsigned modinv(const BigInteger &x, const BigUnsigned &n) {
BigInteger g, r, s;
extendedEuclidean(x, n, g, r, s);
if (g == 1)
// r*x + s*n == 1, so r*x === 1 (mod n), so r is the answer.
return (r % n).getMagnitude(); // (r % n) will be nonnegative
else
throw "BigInteger modinv: x and n have a common factor";
}
int main()
{
int a, b;
scanf("%d %d", &a, &b);
int ans = extendedEuclidean(a, b);
printf("Inverse of %d mod %d = %d\n", b, a, ans);
return 0;
}
Mod Mod::inv(long r0) {
return Mod(extendedEuclidean(r0, modulus));
}
int main(int argc, char **argv) {
//test addition, subtraction
string a = charToS(0x0f);
string b = charToS(0x01);
for(int i=0; i<a.len; i++) a.c[i]=0xFF;
string r = bigIntAdd(a,b);
//printsint(a);printf(" + ");printsint(b);printf(" = ");printsint(r);PRINTNL;
//a=newBigInt(r.c, r.len, -1);
//printsint(a);printf(" + ");printsint(b);printf(" = ");printsint(bigIntAdd(a,b));PRINTNL;
/*a = randString(3);
a.sign = -1;
b=charToS(0xa5);
r = bigIntAdd(a,b);
printsint(a);printf(" + ");printsint(b);printf(" = ");printsint(r);
r = bigIntAdd(b,a);
printf(" = ");printsint(r);PRINTNL;*/
srand(time(NULL));
a = randString(4);
b = randString(2);
//printsint(a);printf(" / \n");
//printsint(b);printf(" = \n");
string *qr = bigIntDivide(a, b);
//printsint(qr[0]);printf(" R: "); printsint(qr[1]);PRINTNL;
if(bigIntComp(a,bigIntAdd(bigIntMultiply(b,qr[0]),qr[1]))==0) {
printf("Division checks out!\n");
}
string n;
if(1) {
string *gcd;
do {
a = randString(5);
b = randString(5);
n = randString(3);
gcd = extendedEuclidean(a,b,n);
} while(gcd==NULL);
printsint(a);
printf("*");
printsint(gcd[0]);
printf("+");
printsint(b);
printf("*");
printsint(gcd[1]);
printf("=");
printsint(n);
PRINTNL;
if(bigIntComp(bigIntAdd(bigIntMultiply(a,gcd[0]),bigIntMultiply(b,gcd[1])),n)==0) {
printf("EGCD working.\n");
}
else printf("EGCD failed!\n");
fflush(stdout);
}
//testing Montgometry reduction product
/*a = charToS(0x02);
n = charToS(0x05);
r = charToS(0x01);
int rpow=0;
while(bigIntComp(r,n)==-1){
r = stringLeftShift(r,1);
rpow++;
}
//printf("r = ");printsint(r);PRINTNL;
string nprime = extendedEuclidean(r,n,charToS(0x01))[1];
nprime.sign = 1;
//printf("nprime = ");printsint(nprime);PRINTNL;fflush(stdout);
string abar = bigIntDivide(bigIntMultiply(a,r),n)[1];
//printf("abar = "); printsint(abar);PRINTNL;fflush(stdout);
printsint(a);printf(" ** 2 mod ");printsint(n);printf(" = ...");PRINTNL;
string rbar = __monPro(abar, abar, n, nprime, rpow);
r = __monPro(rbar, charToS(0x01), n, nprime, rpow);
printf("...");printsint(r);PRINTNL;*/
//testing modexp;
a = base16Decode(newString("0177",0));
b = base16Decode(newString("f9",0));
n = base16Decode(newString("0184",0));
printsint(a);
printf(" ** ");
printsint(b);
printf(" mod ");
printsint(n);
printf(" = \n");
printsint(bigIntModExp(a,b,n));
PRINTNL;
}
