int ecc_octet2point ( point_t *P, uint8_t *octet, uint16_t octet_len )
{
NN_DIGIT alpha[NUMWORDS], tmp[NUMWORDS];
if ( octet[0] == 0 ) { //infinity
NN_AssignZero ( P->x, NUMWORDS );
NN_AssignZero ( P->y, NUMWORDS );
} else if ( octet[0] == 4 ) { //non compressed
NN_Decode ( P->x, NUMWORDS, octet+1, KEYDIGITS*NN_DIGIT_LEN );
NN_Decode ( P->y, NUMWORDS, octet+1+KEYDIGITS*NN_DIGIT_LEN, KEYDIGITS*NN_DIGIT_LEN );
return 2*KEYDIGITS*NN_DIGIT_LEN+1;
} else if ( octet[0] == 2 || octet[0] == 3 ) { //compressed form
NN_Decode ( P->x, NUMWORDS, octet+1, KEYDIGITS*NN_DIGIT_LEN );
//compute y
NN_ModSqrOpt ( alpha, P->x, param.p, param.omega, NUMWORDS );
NN_ModMultOpt ( alpha, alpha, P->x, param.p, param.omega, NUMWORDS );
NN_ModMultOpt ( tmp, param.E.a, P->x, param.p, param.omega, NUMWORDS );
NN_ModAdd ( tmp, tmp, alpha, param.p, NUMWORDS );
NN_ModAdd ( tmp, tmp, param.E.b, param.p, NUMWORDS );
NN_ModSqrOpt ( P->y, tmp, param.p, NUMWORDS, param.omega );
if ( octet[0] == 3 ) {
NN_ModSub ( P->y, param.p, P->y, param.p, NUMWORDS );
}
return KEYDIGITS*NN_DIGIT_LEN+1;
}
return -1;
}
/*---------------------------------------------------------------------------*/
void
ecc_m_dbl_projective(point_t * P0, NN_DIGIT *Z0, uint8_t m)
{
uint8_t i;
NN_DIGIT W[NUMWORDS];
NN_DIGIT A[NUMWORDS];
NN_DIGIT B[NUMWORDS];
NN_DIGIT t1[NUMWORDS];
NN_DIGIT y2[NUMWORDS];
if(NN_Zero(Z0, NUMWORDS)){
return;
}
/* P0->y = 2*P0->y */
NN_LShift(P0->y, P0->y, 1, NUMWORDS);
NN_ModSmall(P0->y, param.p, NUMWORDS);
/* W = Z^4 */
NN_ModSqrOpt(W, Z0, param.p, param.omega, NUMWORDS);
NN_ModSqrOpt(W, W, param.p, param.omega, NUMWORDS);
for(i=0; i<m; i++) {
if(param.E.a_minus3) {
/* A = 3(X^2-W) */
NN_ModSqrOpt(A, P0->x, param.p, param.omega, NUMWORDS);
NN_ModSub(A, A, W, param.p, NUMWORDS);
NN_LShift(t1, A, 1, NUMWORDS);
NN_ModSmall(t1, param.p, NUMWORDS);
NN_ModAdd(A, A, t1, param.p, NUMWORDS);
} else if(param.E.a_zero) {
/* A = 3*X^2 */
NN_ModSqrOpt(t1, P0->x, param.p, param.omega, NUMWORDS);
NN_LShift(A, t1, 1, NUMWORDS);
NN_ModSmall(A, param.p, NUMWORDS);
NN_ModAdd(A, A, t1, param.p, NUMWORDS);
} else {
/* A = 3*X^2 + a*W */
NN_ModSqrOpt(t1, P0->x, param.p, param.omega, NUMWORDS);
NN_LShift(A, t1, 1, NUMWORDS);
NN_ModSmall(A, param.p, NUMWORDS);
NN_ModAdd(A, A, t1, param.p, NUMWORDS);
NN_ModMultOpt(t1, param.E.a, W, param.p, param.omega, NUMWORDS);
NN_ModAdd(A, A, t1, param.p, NUMWORDS);
}
/* B = X*Y^2 */
NN_ModSqrOpt(y2, P0->y, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(B, P0->x, y2, param.p, param.omega, NUMWORDS);
/* X = A^2 - 2B */
NN_ModSqrOpt(P0->x, A, param.p, param.omega, NUMWORDS);
NN_LShift(t1, B, 1, NUMWORDS);
NN_ModSmall(t1, param.p, NUMWORDS);
NN_ModSub(P0->x, P0->x, t1, param.p, NUMWORDS);
/* Z = Z*Y */
NN_ModMultOpt(Z0, Z0, P0->y, param.p, param.omega, NUMWORDS);
NN_ModSqrOpt(y2, y2, param.p, param.omega, NUMWORDS);
if (i < m-1) {
/* W = W*Y^4 */
NN_ModMultOpt(W, W, y2, param.p, param.omega, NUMWORDS);
}
/* Y = 2A(B-X)-Y^4 */
NN_LShift(A, A, 1, NUMWORDS);
NN_ModSmall(A, param.p, NUMWORDS);
NN_ModSub(B, B, P0->x, param.p, NUMWORDS);
NN_ModMultOpt(A, A, B, param.p, param.omega, NUMWORDS);
NN_ModSub(P0->y, A, y2, param.p, NUMWORDS);
}
if((P0->y[0] % 2) == 1) {
NN_Add(P0->y, P0->y, param.p, NUMWORDS);
}
NN_RShift(P0->y, P0->y, 1, NUMWORDS);
}
/*---------------------------------------------------------------------------*/
void
ecc_add_proj(point_t * P0, NN_DIGIT *Z0, point_t * P1, NN_DIGIT * Z1, point_t * P2, NN_DIGIT * Z2)
{
NN_DIGIT n0[NUMWORDS];
NN_DIGIT n1[NUMWORDS];
NN_DIGIT n2[NUMWORDS];
NN_DIGIT n3[NUMWORDS];
NN_DIGIT n4[NUMWORDS];
NN_DIGIT n5[NUMWORDS];
NN_DIGIT n6[NUMWORDS];
if(NN_Zero(Z1, NUMWORDS)) {
p_copy(P0, P2);
NN_Assign(Z0, Z2, NUMWORDS);
return;
}
if(NN_Zero(Z2, NUMWORDS)) {
p_copy(P0, P1);
NN_Assign(Z0, Z1, NUMWORDS);
return;
}
/* double */
if(p_equal(P1, P2)) {
ecc_dbl_proj(P0, Z0, P1, Z1);
return;
}
/* add_proj
* n1, n2
*/
if(Z_is_one(Z2)) {
/* n1 = P1->x, n2 = P1->y */
NN_Assign(n1, P1->x, NUMWORDS);
NN_Assign(n2, P1->y, NUMWORDS);
} else {
/* n1 = P1->x * Z2^2 */
NN_ModSqrOpt(n0, Z2, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n1, P1->x, n0, param.p, param.omega, NUMWORDS);
/* n2 = P1->y * Z2^3 */
NN_ModMultOpt(n0, n0, Z2, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n2, P1->y, n0, param.p, param.omega, NUMWORDS);
}
/* n3, n4 */
if(Z_is_one(Z1)) {
/* n3 = P2->x, n4 = P2->y */
NN_Assign(n3, P2->x, NUMWORDS);
NN_Assign(n4, P2->y, NUMWORDS);
} else {
/* n3 = P2->x * Z1^2 */
NN_ModSqrOpt(n0, Z1, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n3, P2->x, n0, param.p, param.omega, NUMWORDS);
/* n4 = P2->y * Z1^3 */
NN_ModMultOpt(n0, n0, Z1, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n4, P2->y, n0, param.p, param.omega, NUMWORDS);
}
/* n5 = n1 - n3, n6 = n2 - n4 */
NN_ModSub(n5, n1, n3, param.p, NUMWORDS);
NN_ModSub(n6, n2, n4, param.p, NUMWORDS);
if(NN_Zero(n5, NUMWORDS)) {
if(NN_Zero(n6, NUMWORDS)) {
/* P1 and P2 are same point */
ecc_dbl_proj(P0, Z0, P1, Z1);
return;
}
} else {
/* P1 is the inverse of P2 */
NN_AssignZero(Z0, NUMWORDS);
return;
}
/* 'n7' = n1 + n3, 'n8' = n2 + n4 */
NN_ModAdd(n1, n1, n3, param.p, NUMWORDS);
NN_ModAdd(n2, n2, n4, param.p, NUMWORDS);
/* Z0 = Z1 * Z2 * n5 */
if(Z_is_one(Z1) && Z_is_one(Z2)) {
NN_Assign(Z0, n5, NUMWORDS);
} else {
if(Z_is_one(Z1)) {
NN_Assign(n0, Z2, NUMWORDS);
} else if(Z_is_one(Z2)) {
NN_Assign(n0, Z1, NUMWORDS);
} else {
NN_ModMultOpt(n0, Z1, Z2, param.p, param.omega, NUMWORDS);
}
NN_ModMultOpt(Z0, n0, n5, param.p, param.omega, NUMWORDS);
}
/* P0->x = n6^2 - n5^2 * 'n7' */
NN_ModSqrOpt(n0, n6, param.p, param.omega, NUMWORDS);
NN_ModSqrOpt(n4, n5, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n3, n1, n4, param.p, param.omega, NUMWORDS);
NN_ModSub(P0->x, n0, n3, param.p, NUMWORDS);
/* 'n9' = n5^2 * 'n7' - 2 * P0->x */
NN_LShift(n0, P0->x, 1, NUMWORDS);
NN_ModSmall(n0, param.p, NUMWORDS);
NN_ModSub(n0, n3, n0, param.p, NUMWORDS);
/* P0->y = (n6 * 'n9' - 'n8' * 'n5^3') / 2 */
NN_ModMultOpt(n0, n0, n6, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n5, n4, n5, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n1, n2, n5, param.p, param.omega, NUMWORDS);
NN_ModSub(n0, n0, n1, param.p, NUMWORDS);
if((n0[0] % 2) == 1) {
NN_Add(n0, n0, param.p, NUMWORDS);
}
NN_RShift(P0->y, n0, 1, NUMWORDS);
}
/*---------------------------------------------------------------------------*/
void
ecc_dbl_proj(point_t * P0, NN_DIGIT *Z0, point_t * P1, NN_DIGIT * Z1)
{
NN_DIGIT n0[NUMWORDS];
NN_DIGIT n1[NUMWORDS];
NN_DIGIT n2[NUMWORDS];
NN_DIGIT n3[NUMWORDS];
if(NN_Zero(Z1, NUMWORDS)) {
NN_AssignZero(Z0, NUMWORDS);
return;
}
// n1
if(Z_is_one(Z1)) {
/* n1 = 3 * P1->x^2 + param.E.a */
NN_ModSqrOpt(n0, P1->x, param.p, param.omega, NUMWORDS);
NN_LShift(n1, n0, 1, NUMWORDS);
NN_ModSmall(n1, param.p, NUMWORDS);
NN_ModAdd(n0, n0, n1, param.p, NUMWORDS);
NN_ModAdd(n1, n0, param.E.a, param.p, NUMWORDS);
} else {
if(param.E.a_minus3) {
/* for a = -3
* n1 = 3 * (X1 + Z1^2) * (X1 - Z1^2) = 3 * X1^2 - 3 * Z1^4
*/
NN_ModSqrOpt(n1, Z1, param.p, param.omega, NUMWORDS);
NN_ModAdd(n0, P1->x, n1, param.p, NUMWORDS);
NN_ModSub(n2, P1->x, n1, param.p, NUMWORDS);
NN_ModMultOpt(n1, n0, n2, param.p, param.omega, NUMWORDS);
NN_LShift(n0, n1, 1, NUMWORDS);
NN_ModSmall(n0, param.p, NUMWORDS);
NN_ModAdd(n1, n0, n1, param.p, NUMWORDS);
} else if (param.E.a_zero) {
/* n1 = 3 * P1->x^2 */
NN_ModSqrOpt(n0, P1->x, param.p, param.omega, NUMWORDS);
NN_LShift(n1, n0, 1, NUMWORDS);
NN_ModSmall(n1, param.p, NUMWORDS);
NN_ModAdd(n1, n0, n1, param.p, NUMWORDS);
} else {
/* n1 = 3 * P1->x^2 + param.E.a * Z1^4 */
NN_ModSqrOpt(n0, P1->x, param.p, param.omega, NUMWORDS);
NN_LShift(n1, n0, 1, NUMWORDS);
NN_ModSmall(n1, param.p, NUMWORDS);
NN_ModAdd(n0, n0, n1, param.p, NUMWORDS);
NN_ModSqrOpt(n1, Z1, param.p, param.omega, NUMWORDS);
NN_ModSqrOpt(n1, n1, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n1, n1, param.E.a, param.p, param.omega, NUMWORDS);
NN_ModAdd(n1, n1, n0, param.p, NUMWORDS);
}
}
/* Z0 = 2 * P1->y * Z1 */
if(Z_is_one(Z1)) {
NN_Assign(n0, P1->y, NUMWORDS);
} else {
NN_ModMultOpt(n0, P1->y, Z1, param.p, param.omega, NUMWORDS);
}
NN_LShift(Z0, n0, 1, NUMWORDS);
NN_ModSmall(Z0, param.p, NUMWORDS);
/* n2 = 4 * P1->x * P1->y^2 */
NN_ModSqrOpt(n3, P1->y, param.p, param.omega, NUMWORDS);
NN_ModMultOpt(n2, P1->x, n3, param.p, param.omega, NUMWORDS);
NN_LShift(n2, n2, 2, NUMWORDS);
NN_ModSmall(n2, param.p, NUMWORDS);
/* P0->x = n1^2 - 2 * n2 */
NN_LShift(n0, n2, 1, NUMWORDS);
NN_ModSmall(n0, param.p, NUMWORDS);
NN_ModSqrOpt(P0->x, n1, param.p, param.omega, NUMWORDS);
NN_ModSub(P0->x, P0->x, n0, param.p, NUMWORDS);
/* n3 = 8 * P1->y^4 */
NN_ModSqrOpt(n0, n3, param.p, param.omega, NUMWORDS);
NN_LShift(n3, n0, 3, NUMWORDS);
NN_ModSmall(n3, param.p, NUMWORDS);
/* P0->y = n1 * (n2 - P0->x) - n3 */
NN_ModSub(n0, n2, P0->x, param.p, NUMWORDS);
NN_ModMultOpt(n0, n1, n0, param.p, param.omega, NUMWORDS);
NN_ModSub(P0->y, n0, n3, param.p, NUMWORDS);
}
static void
c_add_mix(point_t * P0, NN_DIGIT *Z0, point_t * P1, NN_DIGIT * Z1, point_t * P2)
{
NN_DIGIT t1[NUMWORDS];
NN_DIGIT t2[NUMWORDS];
NN_DIGIT t3[NUMWORDS];
NN_DIGIT t4[NUMWORDS];
NN_DIGIT Z2[NUMWORDS];
/* P2 == infinity */
if(NN_Zero(P2->x, NUMWORDS)) {
if(NN_Zero(P2->y, NUMWORDS)) {
p_copy(P0, P1);
NN_Assign(Z0, Z1, NUMWORDS);
return;
}
}
/* P1 == infinity */
if(NN_Zero(Z1, NUMWORDS)) {
p_copy(P0, P2);
NN_AssignDigit(Z0, 1, NUMWORDS);
return;
}
/* T1 = Z1^2 */
NN_ModSqrOpt(t1, Z1, param.p, param.omega, NUMWORDS);
/* T2 = T1*Z1 */
NN_ModMultOpt(t2, t1, Z1, param.p, param.omega, NUMWORDS);
/* T1 = T1*P2->x */
NN_ModMultOpt(t1, t1, P2->x, param.p, param.omega, NUMWORDS);
/* T2 = T2*P2->y */
NN_ModMultOpt(t2, t2, P2->y, param.p, param.omega, NUMWORDS);
/* T1 = T1-P1->x */
NN_ModSub(t1, t1, P1->x, param.p, NUMWORDS);
/* T2 = T2-P1->y */
NN_ModSub(t2, t2, P1->y, param.p, NUMWORDS);
if(NN_Zero(t1, NUMWORDS)) {
if(NN_Zero(t2, NUMWORDS)) {
NN_AssignDigit(Z2, 1, NUMWORDS);
ecc_dbl_proj(P0, Z0, P2, Z2);
return;
} else {
NN_AssignDigit(Z0, 0, NUMWORDS);
return;
}
}
/* Z3 = Z1*T1 */
NN_ModMultOpt(Z0, Z1, t1, param.p, param.omega, NUMWORDS);
/* T3 = T1^2 */
NN_ModSqrOpt(t3, t1, param.p, param.omega, NUMWORDS);
/* T4 = T3*T1 */
NN_ModMultOpt(t4, t3, t1, param.p, param.omega, NUMWORDS);
/* T3 = T3*P1->x */
NN_ModMultOpt(t3, t3, P1->x, param.p, param.omega, NUMWORDS);
/* T1 = 2*T3 */
NN_LShift(t1, t3, 1, NUMWORDS);
NN_ModSmall(t1, param.p, NUMWORDS);
/* P0->x = T2^2 */
NN_ModSqrOpt(P0->x, t2, param.p, param.omega, NUMWORDS);
/* P0->x = P0->x-T1 */
NN_ModSub(P0->x, P0->x, t1, param.p, NUMWORDS);
/* P0->x = P0->x-T4 */
NN_ModSub(P0->x, P0->x, t4, param.p, NUMWORDS);
/* T3 = T3-P0->x */
NN_ModSub(t3, t3, P0->x, param.p, NUMWORDS);
/* T3 = T3*T2 */
NN_ModMultOpt(t3, t3, t2, param.p, param.omega, NUMWORDS);
/* T4 = T4*P1->y */
NN_ModMultOpt(t4, t4, P1->y, param.p, param.omega, NUMWORDS);
/* P0->y = T3-T4 */
NN_ModSub(P0->y, t3, t4, param.p, NUMWORDS);
return;
}