Simplify ec_GFp_nistp224_points_mul logic.
Passing in an array of scalars was removed some time ago, but a few
remnants of it remain.
Change-Id: Id75abedf60b1eab59f24bf7232187675b63291ab
Reviewed-on: https://boringssl-review.googlesource.com/13056
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/crypto/ec/p224-64.c b/crypto/ec/p224-64.c
index b948b31..7b2ae68 100644
--- a/crypto/ec/p224-64.c
+++ b/crypto/ec/p224-64.c
@@ -885,14 +885,12 @@
}
/* Interleaved point multiplication using precomputed point multiples:
- * The small point multiples 0*P, 1*P, ..., 16*P are in pre_comp[],
- * the scalars in scalars[]. If g_scalar is non-NULL, we also add this multiple
+ * The small point multiples 0*P, 1*P, ..., 16*P are in p_pre_comp, the scalars
+ * in p_scalar, if non-NULL. If g_scalar is non-NULL, we also add this multiple
* of the generator, using certain (large) precomputed multiples in g_pre_comp.
* Output point (X, Y, Z) is stored in x_out, y_out, z_out */
-static void batch_mul(felem x_out, felem y_out, felem z_out,
- const felem_bytearray scalars[],
- const size_t num_points, const u8 *g_scalar,
- const felem pre_comp[][17][3]) {
+static void batch_mul(felem x_out, felem y_out, felem z_out, const u8 *p_scalar,
+ const u8 *g_scalar, const felem p_pre_comp[17][3]) {
felem nq[3], tmp[4];
u64 bits;
u8 sign, digit;
@@ -900,11 +898,11 @@
/* set nq to the point at infinity */
OPENSSL_memset(nq, 0, 3 * sizeof(felem));
- /* Loop over all scalars msb-to-lsb, interleaving additions
- * of multiples of the generator (two in each of the last 28 rounds)
- * and additions of other points multiples (every 5th round). */
+ /* Loop over both scalars msb-to-lsb, interleaving additions of multiples of
+ * the generator (two in each of the last 28 rounds) and additions of p (every
+ * 5th round). */
int skip = 1; /* save two point operations in the first round */
- size_t i = num_points != 0 ? 220 : 27;
+ size_t i = p_scalar != NULL ? 220 : 27;
for (;;) {
/* double */
if (!skip) {
@@ -941,30 +939,26 @@
}
/* do other additions every 5 doublings */
- if (num_points != 0 && i % 5 == 0) {
- /* loop over all scalars */
- size_t num;
- for (num = 0; num < num_points; ++num) {
- bits = get_bit(scalars[num], i + 4) << 5;
- bits |= get_bit(scalars[num], i + 3) << 4;
- bits |= get_bit(scalars[num], i + 2) << 3;
- bits |= get_bit(scalars[num], i + 1) << 2;
- bits |= get_bit(scalars[num], i) << 1;
- bits |= get_bit(scalars[num], i - 1);
- ec_GFp_nistp_recode_scalar_bits(&sign, &digit, bits);
+ if (p_scalar != NULL && i % 5 == 0) {
+ bits = get_bit(p_scalar, i + 4) << 5;
+ bits |= get_bit(p_scalar, i + 3) << 4;
+ bits |= get_bit(p_scalar, i + 2) << 3;
+ bits |= get_bit(p_scalar, i + 1) << 2;
+ bits |= get_bit(p_scalar, i) << 1;
+ bits |= get_bit(p_scalar, i - 1);
+ ec_GFp_nistp_recode_scalar_bits(&sign, &digit, bits);
- /* select the point to add or subtract */
- select_point(digit, 17, pre_comp[num], tmp);
- felem_neg(tmp[3], tmp[1]); /* (X, -Y, Z) is the negative point */
- copy_conditional(tmp[1], tmp[3], sign);
+ /* select the point to add or subtract */
+ select_point(digit, 17, p_pre_comp, tmp);
+ felem_neg(tmp[3], tmp[1]); /* (X, -Y, Z) is the negative point */
+ copy_conditional(tmp[1], tmp[3], sign);
- if (!skip) {
- point_add(nq[0], nq[1], nq[2], nq[0], nq[1], nq[2], 0 /* mixed */,
- tmp[0], tmp[1], tmp[2]);
- } else {
- OPENSSL_memcpy(nq, tmp, 3 * sizeof(felem));
- skip = 0;
- }
+ if (!skip) {
+ point_add(nq[0], nq[1], nq[2], nq[0], nq[1], nq[2], 0 /* mixed */,
+ tmp[0], tmp[1], tmp[2]);
+ } else {
+ OPENSSL_memcpy(nq, tmp, 3 * sizeof(felem));
+ skip = 0;
}
}
@@ -1022,30 +1016,16 @@
return 1;
}
-static int ec_GFp_nistp224_points_mul(const EC_GROUP *group,
- EC_POINT *r,
- const BIGNUM *g_scalar,
- const EC_POINT *p_,
- const BIGNUM *p_scalar_,
- BN_CTX *ctx) {
- /* TODO: This function used to take |points| and |scalars| as arrays of
- * |num| elements. The code below should be simplified to work in terms of
- * |p_| and |p_scalar_|. */
- size_t num = p_ != NULL ? 1 : 0;
- const EC_POINT **points = p_ != NULL ? &p_ : NULL;
- BIGNUM const *const *scalars = p_ != NULL ? &p_scalar_ : NULL;
-
+static int ec_GFp_nistp224_points_mul(const EC_GROUP *group, EC_POINT *r,
+ const BIGNUM *g_scalar, const EC_POINT *p,
+ const BIGNUM *p_scalar, BN_CTX *ctx) {
int ret = 0;
BN_CTX *new_ctx = NULL;
BIGNUM *x, *y, *z, *tmp_scalar;
- felem_bytearray g_secret;
- felem_bytearray *secrets = NULL;
- felem(*pre_comp)[17][3] = NULL;
+ felem_bytearray g_secret, p_secret;
+ felem p_pre_comp[17][3];
felem_bytearray tmp;
- size_t num_points = num;
felem x_in, y_in, z_in, x_out, y_out, z_out;
- const EC_POINT *p = NULL;
- const BIGNUM *p_scalar = NULL;
if (ctx == NULL) {
ctx = BN_CTX_new();
@@ -1063,69 +1043,47 @@
goto err;
}
- if (num_points > 0) {
- secrets = OPENSSL_malloc(num_points * sizeof(felem_bytearray));
- pre_comp = OPENSSL_malloc(num_points * sizeof(felem[17][3]));
- if (secrets == NULL ||
- pre_comp == NULL) {
- OPENSSL_PUT_ERROR(EC, ERR_R_MALLOC_FAILURE);
+ if (p != NULL && p_scalar != NULL) {
+ /* We treat NULL scalars as 0, and NULL points as points at infinity, i.e.,
+ * they contribute nothing to the linear combination. */
+ OPENSSL_memset(&p_secret, 0, sizeof(p_secret));
+ OPENSSL_memset(&p_pre_comp, 0, sizeof(p_pre_comp));
+ size_t num_bytes;
+ /* reduce g_scalar to 0 <= g_scalar < 2^224 */
+ if (BN_num_bits(p_scalar) > 224 || BN_is_negative(p_scalar)) {
+ /* this is an unusual input, and we don't guarantee
+ * constant-timeness */
+ if (!BN_nnmod(tmp_scalar, p_scalar, &group->order, ctx)) {
+ OPENSSL_PUT_ERROR(EC, ERR_R_BN_LIB);
+ goto err;
+ }
+ num_bytes = BN_bn2bin(tmp_scalar, tmp);
+ } else {
+ num_bytes = BN_bn2bin(p_scalar, tmp);
+ }
+
+ flip_endian(p_secret, tmp, num_bytes);
+ /* precompute multiples */
+ if (!BN_to_felem(x_out, &p->X) ||
+ !BN_to_felem(y_out, &p->Y) ||
+ !BN_to_felem(z_out, &p->Z)) {
goto err;
}
- /* we treat NULL scalars as 0, and NULL points as points at infinity,
- * i.e., they contribute nothing to the linear combination */
- OPENSSL_memset(secrets, 0, num_points * sizeof(felem_bytearray));
- OPENSSL_memset(pre_comp, 0, num_points * 17 * 3 * sizeof(felem));
- for (size_t i = 0; i < num_points; ++i) {
- if (i == num) {
- /* the generator */
- p = EC_GROUP_get0_generator(group);
- p_scalar = g_scalar;
+ felem_assign(p_pre_comp[1][0], x_out);
+ felem_assign(p_pre_comp[1][1], y_out);
+ felem_assign(p_pre_comp[1][2], z_out);
+
+ for (size_t j = 2; j <= 16; ++j) {
+ if (j & 1) {
+ point_add(p_pre_comp[j][0], p_pre_comp[j][1], p_pre_comp[j][2],
+ p_pre_comp[1][0], p_pre_comp[1][1], p_pre_comp[1][2],
+ 0, p_pre_comp[j - 1][0], p_pre_comp[j - 1][1],
+ p_pre_comp[j - 1][2]);
} else {
- /* the i^th point */
- p = points[i];
- p_scalar = scalars[i];
- }
-
- if (p_scalar != NULL && p != NULL) {
- size_t num_bytes;
- /* reduce g_scalar to 0 <= g_scalar < 2^224 */
- if (BN_num_bits(p_scalar) > 224 || BN_is_negative(p_scalar)) {
- /* this is an unusual input, and we don't guarantee
- * constant-timeness */
- if (!BN_nnmod(tmp_scalar, p_scalar, &group->order, ctx)) {
- OPENSSL_PUT_ERROR(EC, ERR_R_BN_LIB);
- goto err;
- }
- num_bytes = BN_bn2bin(tmp_scalar, tmp);
- } else {
- num_bytes = BN_bn2bin(p_scalar, tmp);
- }
-
- flip_endian(secrets[i], tmp, num_bytes);
- /* precompute multiples */
- if (!BN_to_felem(x_out, &p->X) ||
- !BN_to_felem(y_out, &p->Y) ||
- !BN_to_felem(z_out, &p->Z)) {
- goto err;
- }
-
- felem_assign(pre_comp[i][1][0], x_out);
- felem_assign(pre_comp[i][1][1], y_out);
- felem_assign(pre_comp[i][1][2], z_out);
-
- for (size_t j = 2; j <= 16; ++j) {
- if (j & 1) {
- point_add(pre_comp[i][j][0], pre_comp[i][j][1], pre_comp[i][j][2],
- pre_comp[i][1][0], pre_comp[i][1][1], pre_comp[i][1][2],
- 0, pre_comp[i][j - 1][0], pre_comp[i][j - 1][1],
- pre_comp[i][j - 1][2]);
- } else {
- point_double(pre_comp[i][j][0], pre_comp[i][j][1],
- pre_comp[i][j][2], pre_comp[i][j / 2][0],
- pre_comp[i][j / 2][1], pre_comp[i][j / 2][2]);
- }
- }
+ point_double(p_pre_comp[j][0], p_pre_comp[j][1],
+ p_pre_comp[j][2], p_pre_comp[j / 2][0],
+ p_pre_comp[j / 2][1], p_pre_comp[j / 2][2]);
}
}
}
@@ -1147,9 +1105,9 @@
flip_endian(g_secret, tmp, num_bytes);
}
- batch_mul(x_out, y_out, z_out, (const felem_bytearray(*))secrets,
- num_points, g_scalar != NULL ? g_secret : NULL,
- (const felem(*)[17][3])pre_comp);
+ batch_mul(x_out, y_out, z_out,
+ (p != NULL && p_scalar != NULL) ? p_secret : NULL,
+ g_scalar != NULL ? g_secret : NULL, (const felem(*)[3])p_pre_comp);
/* reduce the output to its unique minimal representation */
felem_contract(x_in, x_out);
@@ -1166,8 +1124,6 @@
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
- OPENSSL_free(secrets);
- OPENSSL_free(pre_comp);
return ret;
}
