#!/bin/sh
$CC $CFLAGS -Wall -Werror -O2 -std=c99 shamirssecret.c -DTEST -o shamirssecret && ./shamirssecret &&
-$CC $CFLAGS -Wall -Werror -O2 -std=c99 -c shamirssecret.c -o shamirssecret.o &&
+$CC $CFLAGS -Wall -Werror -O2 -c shamirssecret.c -o shamirssecret.o &&
$CC $CFLAGS -Wall -Werror -O2 -std=c99 main.c shamirssecret.o -o shamirssecret
* coefficients[0] == secret, the rest are random values
*/
uint8_t calculateQ(uint8_t coefficients[], uint8_t shares_required, uint8_t x) {
+ uint8_t ret = coefficients[0], i;
CHECKSTATE(x != 0); // q(0) == secret, though so does a[0]
- uint8_t ret = coefficients[0];
- for (uint8_t i = 1; i < shares_required; i++) {
+ for (i = 1; i < shares_required; i++) {
ret = field_add(ret, field_mul(coefficients[i], field_pow(x, i)));
}
return ret;
uint8_t calculateSecret(uint8_t x[], uint8_t q[], uint8_t shares_required) {
// Calculate the x^0 term using a derivation of the forumula at
// http://en.wikipedia.org/wiki/Lagrange_polynomial#Example_2
- uint8_t ret = 0;
- for (uint8_t i = 0; i < shares_required; i++) {
+ uint8_t ret = 0, i, j;
+ for (i = 0; i < shares_required; i++) {
uint8_t temp = q[i];
- for (uint8_t j = 0; j < shares_required; j++) {
+ for (j = 0; j < shares_required; j++) {
if (i == j)
continue;
temp = field_mul(temp, field_neg(x[j]));