int ecc_check_point ( point_t *P )
{
NN_DIGIT tmp1[NUMWORDS], tmp2[NUMWORDS];
if ( NN_Zero ( P->x, NUMWORDS ) )
return -1;
if ( NN_Cmp ( P->x, param.p, NUMWORDS ) >= 0 )
return -1;
if ( NN_Zero ( P->y, NUMWORDS ) )
return -1;
if ( NN_Cmp ( P->y, param.p, NUMWORDS ) >= 0 )
return -1;
memset ( tmp1, 0, NUMWORDS*NN_DIGIT_LEN );
memset ( tmp2, 0, NUMWORDS*NN_DIGIT_LEN );
NN_ModSqrOpt ( tmp2, P->x, param.p, param.omega, NUMWORDS );
NN_ModMultOpt ( tmp2, tmp2, P->x, param.p, param.omega, NUMWORDS );
NN_ModMultOpt ( tmp1, P->x, param.E.a, param.p, param.omega, NUMWORDS );
NN_ModAdd ( tmp2, tmp1, tmp2, param.p, NUMWORDS );
NN_ModAdd ( tmp2, tmp2, param.E.b, param.p, NUMWORDS );
NN_ModSqrOpt ( tmp1, P->y, param.p, param.omega, NUMWORDS );
if ( NN_Cmp ( tmp1, tmp2, NUMWORDS ) != 0 )
return -2;
return 1;
}
/* Generates a probable prime a between b and c such that a-1 is divisible by d.
Lengths: a[digits], b[digits], c[digits], d[digits].
Assumes b < c, digits < MAX_NN_DIGITS.
Returns RE_NEED_RANDOM if randomStruct not seeded, RE_DATA if
unsuccessful.
*/
int GeneratePrime(NN_DIGIT *a, NN_DIGIT *b, NN_DIGIT *c, NN_DIGIT *d, unsigned int digits, R_RANDOM_STRUCT *randomStruct)
{
int status;
unsigned char block[MAX_NN_DIGITS * NN_DIGIT_LEN];
NN_DIGIT t[MAX_NN_DIGITS], u[MAX_NN_DIGITS];
/* Generate random number between b and c.
*/
if ((status = R_GenerateBytes (block, digits * NN_DIGIT_LEN, randomStruct))!=0) return (status);
NN_Decode (a, digits, block, digits * NN_DIGIT_LEN);
NN_Sub (t, c, b, digits);
NN_ASSIGN_DIGIT (u, 1, digits);
NN_Add (t, t, u, digits);
NN_Mod (a, a, digits, t, digits);
NN_Add (a, a, b, digits);
/* Adjust so that a-1 is divisible by d.
*/
NN_Mod (t, a, digits, d, digits);
NN_Sub (a, a, t, digits);
NN_Add (a, a, u, digits);
if (NN_Cmp (a, b, digits) < 0) NN_Add (a, a, d, digits);
if (NN_Cmp (a, c, digits) > 0) NN_Sub (a, a, d, digits);
/* Search to c in steps of d.
*/
NN_Assign (t, c, digits);
NN_Sub (t, t, d, digits);
while (! ProbablePrime (a, digits)) {
if (NN_Cmp (a, t, digits) > 0) return (RE_DATA);
NN_Add(a, a, d, digits);
};
return (0);
}
/* Returns nonzero iff a has a prime factor in SMALL_PRIMES.
Lengths: a[aDigits].
Assumes aDigits < MAX_NN_DIGITS.
*/
static int SmallFactor(NN_DIGIT *a, unsigned int aDigits)
{
int status;
NN_DIGIT t[1];
unsigned int i;
status = 0;
for (i = 0; i < SMALL_PRIME_COUNT; i++) {
NN_ASSIGN_DIGIT(t, SMALL_PRIMES[i], 1);
if ((aDigits == 1) && ! NN_Cmp (a, t, 1)) break;
NN_Mod(t, a, aDigits, t, 1);
if (NN_Zero(t, 1)) {
status = 1;
break;
};
};
//Zeroize sensitive information.
i = 0;
R_memset((POINTER)t, 0, sizeof (t));
return (status);
}