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Fixes to the formulas.
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@dfaranha
dfaranha committed Mar 14, 2024
1 parent a22aec2 commit 42143dd
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Showing 3 changed files with 76 additions and 111 deletions.
2 changes: 1 addition & 1 deletion include/relic_core.h
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Original file line number Diff line number Diff line change
Expand Up @@ -278,7 +278,7 @@ typedef struct _ctx_t {
/** The distinguished non-square used by the mapping function */
fp_st ep_map_u;
/** Precomputed constants for hashing. */
fp_st ep_map_c[7];
fp_st ep_map_c[5];
#ifdef EP_ENDOM
fp_st beta;
#if EP_MUL == LWNAF || EP_FIX == COMBS || EP_FIX == LWNAF || EP_SIM == INTER || !defined(STRIP)
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46 changes: 4 additions & 42 deletions src/ep/relic_ep_curve.c
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Original file line number Diff line number Diff line change
Expand Up @@ -91,8 +91,6 @@ static void ep_curve_set_map(void) {
dig_t *c2 = ctx->ep_map_c[2];
dig_t *c3 = ctx->ep_map_c[3];
dig_t *c4 = ctx->ep_map_c[4];
dig_t *c5 = ctx->ep_map_c[5];
dig_t *c6 = ctx->ep_map_c[6];

RLC_TRY {
bn_new(t);
Expand Down Expand Up @@ -173,47 +171,11 @@ static void ep_curve_set_map(void) {
fp_mul_dig(c3, c3, 4); /* c3 *= 4 */
}

/* if b = 0, precompute constants. */
if (ep_curve_opt_b() == RLC_ZERO) {
dig_t r = 0;

fp_set_dig(c4, -fp_prime_get_qnr());
fp_neg(c4, c4);

bn_read_raw(t, fp_prime_get(), RLC_FP_DIGS);
bn_sub_dig(t, t, 1);
bn_rsh(t, t, 2);
fp_exp(c5, c4, t);

bn_read_raw(t, fp_prime_get(), RLC_FP_DIGS);
if ((t->dp[0] & 0xF) == 5) {
/* n = (3p + 1)/16 */
bn_mul_dig(t, t, 3);
bn_add_dig(t, t, 1);
r = 1;
} else {
/* n = (p + 3)/16 */
bn_add_dig(t, t, 3);
r = 3;
}
bn_rsh(t, t, 4);
/* Compute d = 1/c^n. */
fp_exp(c4, c4, t);
fp_inv(c4, c4);
fp_exp_dig(c5, c5, r);
/* Compute 1/sqrt(-1) as well. */
fp_set_dig(c6, 1);
fp_neg(c6, c6);
fp_srt(c6, c6);
}

/* If a = 0, precompute and store a square root of -3. */
if (ep_curve_opt_a() == RLC_ZERO) {
fp_set_dig(c4, 3);
fp_neg(c4, c4);
if (!fp_srt(c4, c4)) {
RLC_THROW(ERR_NO_VALID);
}
fp_set_dig(c4, 3);
fp_neg(c4, c4);
if (!fp_srt(c4, c4)) {
RLC_THROW(ERR_NO_VALID);
}
}
RLC_CATCH_ANY {
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139 changes: 71 additions & 68 deletions src/ep/relic_ep_map.c
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Original file line number Diff line number Diff line change
Expand Up @@ -291,8 +291,6 @@ void ep_map_swift(ep_t p, const uint8_t *msg, size_t len) {
fp_copy(a, ep_curve_get_a());

if (ep_curve_opt_b() == RLC_ZERO) {
fp_set_dig(u, 1);
fp_set_dig(t, 2);
fp_sqr(a, u);
fp_sqr(b, a);
fp_mul(c, b, a);
Expand All @@ -309,10 +307,10 @@ void ep_map_swift(ep_t p, const uint8_t *msg, size_t len) {

fp_sqr(w, b);
fp_mul(y, v, a);
fp_add(y, y, d);
fp_add(y, y, d);
fp_add(y, y, d);
fp_add(y, y, d);
fp_add(y, y, c);
fp_add(y, y, c);
fp_add(y, y, c);
fp_add(y, y, c);
fp_mul(y, y, p->x);

fp_add(den[0], c, v);
Expand All @@ -330,69 +328,74 @@ void ep_map_swift(ep_t p, const uint8_t *msg, size_t len) {
fp_mul(den[2], den[2], b);
fp_mul(den[2], den[2], d);

fp_inv_sim(den, den, 3);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_add(y1, a, v);
fp_dbl(y1, y1);
fp_dbl(y1, y1);
fp_add(y1, y1, w);
fp_mul(z1, y, p->x);
fp_add(x1, x1, z1);
fp_add(y1, y1, y);
fp_add(z1, a, b);
fp_add(z1, z1, b);
fp_add(z1, z1, b);
fp_add(z1, z1, b);
fp_dbl(t, z1);
fp_add(z1, z1, t);
fp_add(z1, z1, c);
fp_sub(z1, z1, v);
fp_mul(z1, z1, v);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_add(a, a, w);
fp_mul(u, a, b);
fp_sub(z1, u, z1);
fp_set_dig(d, 64);
fp_sqr(d, d);
fp_add(z1, z1, d);

fp_mul(x1, x1, den[0]);
fp_mul(y1, y1, den[1]);
fp_mul(z1, z1, den[2]);

fp_sqr(t, x1);
fp_add_dig(t, t, 1);
fp_mul(t, t, x1);
fp_sqr(u, y1);
fp_add_dig(u, u, 1);
fp_mul(u, u, y1);
fp_sqr(v, z1);
fp_add_dig(v, v, 1);
fp_mul(v, v, z1);

int c2 = fp_is_sqr(u);
int c3 = fp_is_sqr(v);

dv_swap_cond(t, u, RLC_FP_DIGS, c2);
dv_swap_cond(x1, y1, RLC_FP_DIGS, c2);
dv_swap_cond(t, v, RLC_FP_DIGS, c3);
dv_swap_cond(x1, z1, RLC_FP_DIGS, c3);

if (!fp_srt(t, t)) {
RLC_THROW(ERR_NO_VALID);
}
fp_neg(u, t);
dv_swap_cond(t, u, RLC_FP_DIGS, fp_is_even(t) ^ s);
if (fp_is_zero(den[0]) || fp_is_zero(den[1]) || fp_is_zero(den[2])) {
ep_set_infty(p);
} else {
fp_inv_sim(den, den, 3);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_add(y1, a, v);
fp_dbl(y1, y1);
fp_dbl(y1, y1);
fp_add(y1, y1, w);
fp_mul(z1, y, p->x);
fp_add(x1, y1, z1);
fp_add(y1, y1, y);

fp_add(z1, a, b);
fp_add(z1, z1, b);
fp_add(z1, z1, b);
fp_add(z1, z1, b);
fp_dbl(t, z1);
fp_add(z1, z1, t);
fp_sub(z1, c, z1);
fp_sub(z1, z1, v);
fp_mul(z1, z1, v);
fp_dbl(a, a);
fp_dbl(a, a);
fp_dbl(a, a);
fp_add(a, a, w);
fp_mul(u, a, b);
fp_sub(z1, u, z1);
fp_set_dig(d, 64);
fp_sqr(d, d);
fp_add(z1, z1, d);

fp_mul(x1, x1, den[0]);
fp_mul(y1, y1, den[1]);
fp_mul(z1, z1, den[2]);

fp_sqr(t, x1);
fp_add_dig(t, t, 1);
fp_mul(t, t, x1);
fp_sqr(u, y1);
fp_add_dig(u, u, 1);
fp_mul(u, u, y1);
fp_sqr(v, z1);
fp_add_dig(v, v, 1);
fp_mul(v, v, z1);

fp_copy(p->x, x1);
fp_copy(p->y, t);
fp_set_dig(p->z, 1);
p->coord = BASIC;
int c2 = fp_is_sqr(u);
int c3 = fp_is_sqr(v);

dv_swap_cond(t, u, RLC_FP_DIGS, c2);
dv_swap_cond(x1, y1, RLC_FP_DIGS, c2);
dv_swap_cond(t, v, RLC_FP_DIGS, c3);
dv_swap_cond(x1, z1, RLC_FP_DIGS, c3);

if (!fp_srt(t, t)) {
RLC_THROW(ERR_NO_VALID);
}
fp_neg(u, t);
dv_swap_cond(t, u, RLC_FP_DIGS, fp_is_even(t) ^ s);

fp_copy(p->x, x1);
fp_copy(p->y, t);
fp_set_dig(p->z, 1);
p->coord = BASIC;
}
} else {
/* This is the SwiftEC case per se. */
if (ep_curve_opt_a() != RLC_ZERO) {
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