/**
* Normalizes a point represented in projective coordinates.
*
* @param r - the result.
* @param p - the point to normalize.
*/
void ed_norm(ed_t r, const ed_t p) {
if (ed_is_infty(p)) {
ed_set_infty(r);
return;
}
if (fp_cmp_dig(p->z, 1) == CMP_EQ) {
/* If the point is represented in affine coordinates, we just copy it. */
ed_copy(r, p);
} else {
fp_t z_inv;
fp_null(z_inv);
fp_new(z_inv);
fp_inv(z_inv, p->z);
fp_mul(r->x, p->x, z_inv);
fp_mul(r->y, p->y, z_inv);
#if ED_ADD == EXTND
fp_mul(r->t, p->t, z_inv);
#endif
fp_set_dig(r->z, 1);
fp_free(z_inv);
}
}
void ed_mul_basic(ed_t r, const ed_t p, const bn_t k) {
ed_t t;
ed_null(t);
if (bn_is_zero(k) || ed_is_infty(p)) {
ed_set_infty(r);
return;
}
TRY {
ed_new(t);
ed_copy(t, p);
for (int i = bn_bits(k) - 2; i >= 0; i--) {
ed_dbl(t, t);
if (bn_get_bit(k, i)) {
ed_add(t, t, p);
}
}
ed_norm(r, t);
if (bn_sign(k) == RLC_NEG) {
ed_neg(r, r);
}
}
CATCH_ANY {
THROW(ERR_CAUGHT);
}
FINALLY {
ed_free(t);
}
}
void ed_mul_lwreg(ed_t r, const ed_t p, const bn_t k) {
if (bn_is_zero(k) || ed_is_infty(p)) {
ed_set_infty(r);
return;
}
ed_mul_reg_imp(r, p, k);
}
/*============================================================================*/
int ed_size_bin(const ed_t a, int pack) {
int size = 0;
if (ed_is_infty(a)) {
return 1;
}
size = 1 + FP_BYTES;
if (!pack) {
size += FP_BYTES;
}
return size;
}
void ed_mul_monty(ed_t r, const ed_t p, const bn_t k) {
ed_t t[2];
ed_null(t[0]);
ed_null(t[1]);
if (bn_is_zero(k) || ed_is_infty(p)) {
ed_set_infty(r);
return;
}
TRY {
ed_new(t[0]);
ed_new(t[1]);
ed_set_infty(t[0]);
ed_copy(t[1], p);
for (int i = bn_bits(k) - 1; i >= 0; i--) {
int j = bn_get_bit(k, i);
dv_swap_cond(t[0]->x, t[1]->x, RLC_FP_DIGS, j ^ 1);
dv_swap_cond(t[0]->y, t[1]->y, RLC_FP_DIGS, j ^ 1);
dv_swap_cond(t[0]->z, t[1]->z, RLC_FP_DIGS, j ^ 1);
#if ED_ADD == EXTND
dv_swap_cond(t[0]->t, t[1]->t, RLC_FP_DIGS, j ^ 1);
#endif
ed_add(t[0], t[0], t[1]);
ed_dbl(t[1], t[1]);
dv_swap_cond(t[0]->x, t[1]->x, RLC_FP_DIGS, j ^ 1);
dv_swap_cond(t[0]->y, t[1]->y, RLC_FP_DIGS, j ^ 1);
dv_swap_cond(t[0]->z, t[1]->z, RLC_FP_DIGS, j ^ 1);
#if ED_ADD == EXTND
dv_swap_cond(t[0]->t, t[1]->t, RLC_FP_DIGS, j ^ 1);
#endif
}
ed_norm(r, t[0]);
if (bn_sign(k) == RLC_NEG) {
ed_neg(r, r);
}
} CATCH_ANY {
THROW(ERR_CAUGHT);
}
FINALLY {
ed_free(t[1]);
ed_free(t[0]);
}
}
void ed_write_bin(uint8_t *bin, int len, const ed_t a, int pack) {
ed_t t;
ed_null(t);
if (ed_is_infty(a)) {
if (len != 1) {
THROW(ERR_NO_BUFFER);
} else {
bin[0] = 0;
return;
}
}
TRY {
ed_new(t);
ed_norm(t, a);
if (pack) {
if (len != FP_BYTES + 1) {
THROW(ERR_NO_BUFFER);
} else {
ed_pck(t, t);
bin[0] = 2 | fp_get_bit(t->x, 0);
fp_write_bin(bin + 1, FP_BYTES, t->y);
}
} else {
if (len != 2 * FP_BYTES + 1) {
THROW(ERR_NO_BUFFER);
} else {
bin[0] = 4;
fp_write_bin(bin + 1, FP_BYTES, t->y);
fp_write_bin(bin + FP_BYTES + 1, FP_BYTES, t->x);
}
}
} CATCH_ANY {
THROW(ERR_CAUGHT);
}
FINALLY {
ed_free(t);
}
}
void ed_mul_slide(ed_t r, const ed_t p, const bn_t k) {
ed_t t[1 << (EP_WIDTH - 1)], q;
int i, j, l;
uint8_t win[RLC_FP_BITS + 1];
ed_null(q);
if (bn_is_zero(k) || ed_is_infty(p)) {
ed_set_infty(r);
return;
}
TRY {
for (i = 0; i < (1 << (EP_WIDTH - 1)); i ++) {
ed_null(t[i]);
ed_new(t[i]);
}
ed_new(q);
ed_copy(t[0], p);
ed_dbl(q, p);
#if defined(EP_MIXED)
ed_norm(q, q);
#endif
/* Create table. */
for (i = 1; i < (1 << (EP_WIDTH - 1)); i++) {
ed_add(t[i], t[i - 1], q);
}
#if defined(EP_MIXED)
ed_norm_sim(t + 1, (const ed_t *)t + 1, (1 << (EP_WIDTH - 1)) - 1);
#endif
ed_set_infty(q);
l = RLC_FP_BITS + 1;
bn_rec_slw(win, &l, k, EP_WIDTH);
for (i = 0; i < l; i++) {
if (win[i] == 0) {
ed_dbl(q, q);
} else {
for (j = 0; j < util_bits_dig(win[i]); j++) {
ed_dbl(q, q);
}
ed_add(q, q, t[win[i] >> 1]);
}
}
ed_norm(r, q);
if (bn_sign(k) == RLC_NEG) {
ed_neg(r, r);
}
}
CATCH_ANY {
THROW(ERR_CAUGHT);
}
FINALLY {
for (i = 0; i < (1 << (EP_WIDTH - 1)); i++) {
ed_free(t[i]);
}
ed_free(q);
}
}