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-rw-r--r--lib/mpi/ec.c1509
1 files changed, 1509 insertions, 0 deletions
diff --git a/lib/mpi/ec.c b/lib/mpi/ec.c
new file mode 100644
index 000000000000..c21470122dfc
--- /dev/null
+++ b/lib/mpi/ec.c
@@ -0,0 +1,1509 @@
+/* ec.c - Elliptic Curve functions
+ * Copyright (C) 2007 Free Software Foundation, Inc.
+ * Copyright (C) 2013 g10 Code GmbH
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mpi-internal.h"
+#include "longlong.h"
+
+#define point_init(a) mpi_point_init((a))
+#define point_free(a) mpi_point_free_parts((a))
+
+#define log_error(fmt, ...) pr_err(fmt, ##__VA_ARGS__)
+#define log_fatal(fmt, ...) pr_err(fmt, ##__VA_ARGS__)
+
+#define DIM(v) (sizeof(v)/sizeof((v)[0]))
+
+
+/* Create a new point option. NBITS gives the size in bits of one
+ * coordinate; it is only used to pre-allocate some resources and
+ * might also be passed as 0 to use a default value.
+ */
+MPI_POINT mpi_point_new(unsigned int nbits)
+{
+ MPI_POINT p;
+
+ (void)nbits; /* Currently not used. */
+
+ p = kmalloc(sizeof(*p), GFP_KERNEL);
+ if (p)
+ mpi_point_init(p);
+ return p;
+}
+EXPORT_SYMBOL_GPL(mpi_point_new);
+
+/* Release the point object P. P may be NULL. */
+void mpi_point_release(MPI_POINT p)
+{
+ if (p) {
+ mpi_point_free_parts(p);
+ kfree(p);
+ }
+}
+EXPORT_SYMBOL_GPL(mpi_point_release);
+
+/* Initialize the fields of a point object. gcry_mpi_point_free_parts
+ * may be used to release the fields.
+ */
+void mpi_point_init(MPI_POINT p)
+{
+ p->x = mpi_new(0);
+ p->y = mpi_new(0);
+ p->z = mpi_new(0);
+}
+EXPORT_SYMBOL_GPL(mpi_point_init);
+
+/* Release the parts of a point object. */
+void mpi_point_free_parts(MPI_POINT p)
+{
+ mpi_free(p->x); p->x = NULL;
+ mpi_free(p->y); p->y = NULL;
+ mpi_free(p->z); p->z = NULL;
+}
+EXPORT_SYMBOL_GPL(mpi_point_free_parts);
+
+/* Set the value from S into D. */
+static void point_set(MPI_POINT d, MPI_POINT s)
+{
+ mpi_set(d->x, s->x);
+ mpi_set(d->y, s->y);
+ mpi_set(d->z, s->z);
+}
+
+static void point_resize(MPI_POINT p, struct mpi_ec_ctx *ctx)
+{
+ size_t nlimbs = ctx->p->nlimbs;
+
+ mpi_resize(p->x, nlimbs);
+ p->x->nlimbs = nlimbs;
+ mpi_resize(p->z, nlimbs);
+ p->z->nlimbs = nlimbs;
+
+ if (ctx->model != MPI_EC_MONTGOMERY) {
+ mpi_resize(p->y, nlimbs);
+ p->y->nlimbs = nlimbs;
+ }
+}
+
+static void point_swap_cond(MPI_POINT d, MPI_POINT s, unsigned long swap,
+ struct mpi_ec_ctx *ctx)
+{
+ mpi_swap_cond(d->x, s->x, swap);
+ if (ctx->model != MPI_EC_MONTGOMERY)
+ mpi_swap_cond(d->y, s->y, swap);
+ mpi_swap_cond(d->z, s->z, swap);
+}
+
+
+/* W = W mod P. */
+static void ec_mod(MPI w, struct mpi_ec_ctx *ec)
+{
+ if (ec->t.p_barrett)
+ mpi_mod_barrett(w, w, ec->t.p_barrett);
+ else
+ mpi_mod(w, w, ec->p);
+}
+
+static void ec_addm(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_add(w, u, v);
+ ec_mod(w, ctx);
+}
+
+static void ec_subm(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ec)
+{
+ mpi_sub(w, u, v);
+ while (w->sign)
+ mpi_add(w, w, ec->p);
+ /*ec_mod(w, ec);*/
+}
+
+static void ec_mulm(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_mul(w, u, v);
+ ec_mod(w, ctx);
+}
+
+/* W = 2 * U mod P. */
+static void ec_mul2(MPI w, MPI u, struct mpi_ec_ctx *ctx)
+{
+ mpi_lshift(w, u, 1);
+ ec_mod(w, ctx);
+}
+
+static void ec_powm(MPI w, const MPI b, const MPI e,
+ struct mpi_ec_ctx *ctx)
+{
+ mpi_powm(w, b, e, ctx->p);
+ /* mpi_abs(w); */
+}
+
+/* Shortcut for
+ * ec_powm(B, B, mpi_const(MPI_C_TWO), ctx);
+ * for easier optimization.
+ */
+static void ec_pow2(MPI w, const MPI b, struct mpi_ec_ctx *ctx)
+{
+ /* Using mpi_mul is slightly faster (at least on amd64). */
+ /* mpi_powm(w, b, mpi_const(MPI_C_TWO), ctx->p); */
+ ec_mulm(w, b, b, ctx);
+}
+
+/* Shortcut for
+ * ec_powm(B, B, mpi_const(MPI_C_THREE), ctx);
+ * for easier optimization.
+ */
+static void ec_pow3(MPI w, const MPI b, struct mpi_ec_ctx *ctx)
+{
+ mpi_powm(w, b, mpi_const(MPI_C_THREE), ctx->p);
+}
+
+static void ec_invm(MPI x, MPI a, struct mpi_ec_ctx *ctx)
+{
+ if (!mpi_invm(x, a, ctx->p))
+ log_error("ec_invm: inverse does not exist:\n");
+}
+
+static void mpih_set_cond(mpi_ptr_t wp, mpi_ptr_t up,
+ mpi_size_t usize, unsigned long set)
+{
+ mpi_size_t i;
+ mpi_limb_t mask = ((mpi_limb_t)0) - set;
+ mpi_limb_t x;
+
+ for (i = 0; i < usize; i++) {
+ x = mask & (wp[i] ^ up[i]);
+ wp[i] = wp[i] ^ x;
+ }
+}
+
+/* Routines for 2^255 - 19. */
+
+#define LIMB_SIZE_25519 ((256+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB)
+
+static void ec_addm_25519(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_25519;
+ mpi_limb_t n[LIMB_SIZE_25519];
+ mpi_limb_t borrow;
+
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("addm_25519: different sizes\n");
+
+ memset(n, 0, sizeof(n));
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ mpihelp_add_n(wp, up, vp, wsize);
+ borrow = mpihelp_sub_n(wp, wp, ctx->p->d, wsize);
+ mpih_set_cond(n, ctx->p->d, wsize, (borrow != 0UL));
+ mpihelp_add_n(wp, wp, n, wsize);
+ wp[LIMB_SIZE_25519-1] &= ~((mpi_limb_t)1 << (255 % BITS_PER_MPI_LIMB));
+}
+
+static void ec_subm_25519(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_25519;
+ mpi_limb_t n[LIMB_SIZE_25519];
+ mpi_limb_t borrow;
+
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("subm_25519: different sizes\n");
+
+ memset(n, 0, sizeof(n));
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ borrow = mpihelp_sub_n(wp, up, vp, wsize);
+ mpih_set_cond(n, ctx->p->d, wsize, (borrow != 0UL));
+ mpihelp_add_n(wp, wp, n, wsize);
+ wp[LIMB_SIZE_25519-1] &= ~((mpi_limb_t)1 << (255 % BITS_PER_MPI_LIMB));
+}
+
+static void ec_mulm_25519(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_25519;
+ mpi_limb_t n[LIMB_SIZE_25519*2];
+ mpi_limb_t m[LIMB_SIZE_25519+1];
+ mpi_limb_t cy;
+ int msb;
+
+ (void)ctx;
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("mulm_25519: different sizes\n");
+
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ mpihelp_mul_n(n, up, vp, wsize);
+ memcpy(wp, n, wsize * BYTES_PER_MPI_LIMB);
+ wp[LIMB_SIZE_25519-1] &= ~((mpi_limb_t)1 << (255 % BITS_PER_MPI_LIMB));
+
+ memcpy(m, n+LIMB_SIZE_25519-1, (wsize+1) * BYTES_PER_MPI_LIMB);
+ mpihelp_rshift(m, m, LIMB_SIZE_25519+1, (255 % BITS_PER_MPI_LIMB));
+
+ memcpy(n, m, wsize * BYTES_PER_MPI_LIMB);
+ cy = mpihelp_lshift(m, m, LIMB_SIZE_25519, 4);
+ m[LIMB_SIZE_25519] = cy;
+ cy = mpihelp_add_n(m, m, n, wsize);
+ m[LIMB_SIZE_25519] += cy;
+ cy = mpihelp_add_n(m, m, n, wsize);
+ m[LIMB_SIZE_25519] += cy;
+ cy = mpihelp_add_n(m, m, n, wsize);
+ m[LIMB_SIZE_25519] += cy;
+
+ cy = mpihelp_add_n(wp, wp, m, wsize);
+ m[LIMB_SIZE_25519] += cy;
+
+ memset(m, 0, wsize * BYTES_PER_MPI_LIMB);
+ msb = (wp[LIMB_SIZE_25519-1] >> (255 % BITS_PER_MPI_LIMB));
+ m[0] = (m[LIMB_SIZE_25519] * 2 + msb) * 19;
+ wp[LIMB_SIZE_25519-1] &= ~((mpi_limb_t)1 << (255 % BITS_PER_MPI_LIMB));
+ mpihelp_add_n(wp, wp, m, wsize);
+
+ m[0] = 0;
+ cy = mpihelp_sub_n(wp, wp, ctx->p->d, wsize);
+ mpih_set_cond(m, ctx->p->d, wsize, (cy != 0UL));
+ mpihelp_add_n(wp, wp, m, wsize);
+}
+
+static void ec_mul2_25519(MPI w, MPI u, struct mpi_ec_ctx *ctx)
+{
+ ec_addm_25519(w, u, u, ctx);
+}
+
+static void ec_pow2_25519(MPI w, const MPI b, struct mpi_ec_ctx *ctx)
+{
+ ec_mulm_25519(w, b, b, ctx);
+}
+
+/* Routines for 2^448 - 2^224 - 1. */
+
+#define LIMB_SIZE_448 ((448+BITS_PER_MPI_LIMB-1)/BITS_PER_MPI_LIMB)
+#define LIMB_SIZE_HALF_448 ((LIMB_SIZE_448+1)/2)
+
+static void ec_addm_448(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_448;
+ mpi_limb_t n[LIMB_SIZE_448];
+ mpi_limb_t cy;
+
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("addm_448: different sizes\n");
+
+ memset(n, 0, sizeof(n));
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ cy = mpihelp_add_n(wp, up, vp, wsize);
+ mpih_set_cond(n, ctx->p->d, wsize, (cy != 0UL));
+ mpihelp_sub_n(wp, wp, n, wsize);
+}
+
+static void ec_subm_448(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_448;
+ mpi_limb_t n[LIMB_SIZE_448];
+ mpi_limb_t borrow;
+
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("subm_448: different sizes\n");
+
+ memset(n, 0, sizeof(n));
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ borrow = mpihelp_sub_n(wp, up, vp, wsize);
+ mpih_set_cond(n, ctx->p->d, wsize, (borrow != 0UL));
+ mpihelp_add_n(wp, wp, n, wsize);
+}
+
+static void ec_mulm_448(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx)
+{
+ mpi_ptr_t wp, up, vp;
+ mpi_size_t wsize = LIMB_SIZE_448;
+ mpi_limb_t n[LIMB_SIZE_448*2];
+ mpi_limb_t a2[LIMB_SIZE_HALF_448];
+ mpi_limb_t a3[LIMB_SIZE_HALF_448];
+ mpi_limb_t b0[LIMB_SIZE_HALF_448];
+ mpi_limb_t b1[LIMB_SIZE_HALF_448];
+ mpi_limb_t cy;
+ int i;
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ mpi_limb_t b1_rest, a3_rest;
+#endif
+
+ if (w->nlimbs != wsize || u->nlimbs != wsize || v->nlimbs != wsize)
+ log_bug("mulm_448: different sizes\n");
+
+ up = u->d;
+ vp = v->d;
+ wp = w->d;
+
+ mpihelp_mul_n(n, up, vp, wsize);
+
+ for (i = 0; i < (wsize + 1) / 2; i++) {
+ b0[i] = n[i];
+ b1[i] = n[i+wsize/2];
+ a2[i] = n[i+wsize];
+ a3[i] = n[i+wsize+wsize/2];
+ }
+
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ b0[LIMB_SIZE_HALF_448-1] &= ((mpi_limb_t)1UL << 32)-1;
+ a2[LIMB_SIZE_HALF_448-1] &= ((mpi_limb_t)1UL << 32)-1;
+
+ b1_rest = 0;
+ a3_rest = 0;
+
+ for (i = (wsize + 1) / 2 - 1; i >= 0; i--) {
+ mpi_limb_t b1v, a3v;
+ b1v = b1[i];
+ a3v = a3[i];
+ b1[i] = (b1_rest << 32) | (b1v >> 32);
+ a3[i] = (a3_rest << 32) | (a3v >> 32);
+ b1_rest = b1v & (((mpi_limb_t)1UL << 32)-1);
+ a3_rest = a3v & (((mpi_limb_t)1UL << 32)-1);
+ }
+#endif
+
+ cy = mpihelp_add_n(b0, b0, a2, LIMB_SIZE_HALF_448);
+ cy += mpihelp_add_n(b0, b0, a3, LIMB_SIZE_HALF_448);
+ for (i = 0; i < (wsize + 1) / 2; i++)
+ wp[i] = b0[i];
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ wp[LIMB_SIZE_HALF_448-1] &= (((mpi_limb_t)1UL << 32)-1);
+#endif
+
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ cy = b0[LIMB_SIZE_HALF_448-1] >> 32;
+#endif
+
+ cy = mpihelp_add_1(b1, b1, LIMB_SIZE_HALF_448, cy);
+ cy += mpihelp_add_n(b1, b1, a2, LIMB_SIZE_HALF_448);
+ cy += mpihelp_add_n(b1, b1, a3, LIMB_SIZE_HALF_448);
+ cy += mpihelp_add_n(b1, b1, a3, LIMB_SIZE_HALF_448);
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ b1_rest = 0;
+ for (i = (wsize + 1) / 2 - 1; i >= 0; i--) {
+ mpi_limb_t b1v = b1[i];
+ b1[i] = (b1_rest << 32) | (b1v >> 32);
+ b1_rest = b1v & (((mpi_limb_t)1UL << 32)-1);
+ }
+ wp[LIMB_SIZE_HALF_448-1] |= (b1_rest << 32);
+#endif
+ for (i = 0; i < wsize / 2; i++)
+ wp[i+(wsize + 1) / 2] = b1[i];
+
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ cy = b1[LIMB_SIZE_HALF_448-1];
+#endif
+
+ memset(n, 0, wsize * BYTES_PER_MPI_LIMB);
+
+#if (LIMB_SIZE_HALF_448 > LIMB_SIZE_448/2)
+ n[LIMB_SIZE_HALF_448-1] = cy << 32;
+#else
+ n[LIMB_SIZE_HALF_448] = cy;
+#endif
+ n[0] = cy;
+ mpihelp_add_n(wp, wp, n, wsize);
+
+ memset(n, 0, wsize * BYTES_PER_MPI_LIMB);
+ cy = mpihelp_sub_n(wp, wp, ctx->p->d, wsize);
+ mpih_set_cond(n, ctx->p->d, wsize, (cy != 0UL));
+ mpihelp_add_n(wp, wp, n, wsize);
+}
+
+static void ec_mul2_448(MPI w, MPI u, struct mpi_ec_ctx *ctx)
+{
+ ec_addm_448(w, u, u, ctx);
+}
+
+static void ec_pow2_448(MPI w, const MPI b, struct mpi_ec_ctx *ctx)
+{
+ ec_mulm_448(w, b, b, ctx);
+}
+
+struct field_table {
+ const char *p;
+
+ /* computation routines for the field. */
+ void (*addm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx);
+ void (*subm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx);
+ void (*mulm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx);
+ void (*mul2)(MPI w, MPI u, struct mpi_ec_ctx *ctx);
+ void (*pow2)(MPI w, const MPI b, struct mpi_ec_ctx *ctx);
+};
+
+static const struct field_table field_table[] = {
+ {
+ "0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFED",
+ ec_addm_25519,
+ ec_subm_25519,
+ ec_mulm_25519,
+ ec_mul2_25519,
+ ec_pow2_25519
+ },
+ {
+ "0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE"
+ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+ ec_addm_448,
+ ec_subm_448,
+ ec_mulm_448,
+ ec_mul2_448,
+ ec_pow2_448
+ },
+ { NULL, NULL, NULL, NULL, NULL, NULL },
+};
+
+/* Force recomputation of all helper variables. */
+static void mpi_ec_get_reset(struct mpi_ec_ctx *ec)
+{
+ ec->t.valid.a_is_pminus3 = 0;
+ ec->t.valid.two_inv_p = 0;
+}
+
+/* Accessor for helper variable. */
+static int ec_get_a_is_pminus3(struct mpi_ec_ctx *ec)
+{
+ MPI tmp;
+
+ if (!ec->t.valid.a_is_pminus3) {
+ ec->t.valid.a_is_pminus3 = 1;
+ tmp = mpi_alloc_like(ec->p);
+ mpi_sub_ui(tmp, ec->p, 3);
+ ec->t.a_is_pminus3 = !mpi_cmp(ec->a, tmp);
+ mpi_free(tmp);
+ }
+
+ return ec->t.a_is_pminus3;
+}
+
+/* Accessor for helper variable. */
+static MPI ec_get_two_inv_p(struct mpi_ec_ctx *ec)
+{
+ if (!ec->t.valid.two_inv_p) {
+ ec->t.valid.two_inv_p = 1;
+ if (!ec->t.two_inv_p)
+ ec->t.two_inv_p = mpi_alloc(0);
+ ec_invm(ec->t.two_inv_p, mpi_const(MPI_C_TWO), ec);
+ }
+ return ec->t.two_inv_p;
+}
+
+static const char *const curve25519_bad_points[] = {
+ "0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffed",
+ "0x0000000000000000000000000000000000000000000000000000000000000000",
+ "0x0000000000000000000000000000000000000000000000000000000000000001",
+ "0x00b8495f16056286fdb1329ceb8d09da6ac49ff1fae35616aeb8413b7c7aebe0",
+ "0x57119fd0dd4e22d8868e1c58c45c44045bef839c55b1d0b1248c50a3bc959c5f",
+ "0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffec",
+ "0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffee",
+ NULL
+};
+
+static const char *const curve448_bad_points[] = {
+ "0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffe"
+ "ffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+ "0x00000000000000000000000000000000000000000000000000000000"
+ "00000000000000000000000000000000000000000000000000000000",
+ "0x00000000000000000000000000000000000000000000000000000000"
+ "00000000000000000000000000000000000000000000000000000001",
+ "0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffe"
+ "fffffffffffffffffffffffffffffffffffffffffffffffffffffffe",
+ "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+ "00000000000000000000000000000000000000000000000000000000",
+ NULL
+};
+
+static const char *const *bad_points_table[] = {
+ curve25519_bad_points,
+ curve448_bad_points,
+};
+
+static void mpi_ec_coefficient_normalize(MPI a, MPI p)
+{
+ if (a->sign) {
+ mpi_resize(a, p->nlimbs);
+ mpihelp_sub_n(a->d, p->d, a->d, p->nlimbs);
+ a->nlimbs = p->nlimbs;
+ a->sign = 0;
+ }
+}
+
+/* This function initialized a context for elliptic curve based on the
+ * field GF(p). P is the prime specifying this field, A is the first
+ * coefficient. CTX is expected to be zeroized.
+ */
+void mpi_ec_init(struct mpi_ec_ctx *ctx, enum gcry_mpi_ec_models model,
+ enum ecc_dialects dialect,
+ int flags, MPI p, MPI a, MPI b)
+{
+ int i;
+ static int use_barrett = -1 /* TODO: 1 or -1 */;
+
+ mpi_ec_coefficient_normalize(a, p);
+ mpi_ec_coefficient_normalize(b, p);
+
+ /* Fixme: Do we want to check some constraints? e.g. a < p */
+
+ ctx->model = model;
+ ctx->dialect = dialect;
+ ctx->flags = flags;
+ if (dialect == ECC_DIALECT_ED25519)
+ ctx->nbits = 256;
+ else
+ ctx->nbits = mpi_get_nbits(p);
+ ctx->p = mpi_copy(p);
+ ctx->a = mpi_copy(a);
+ ctx->b = mpi_copy(b);
+
+ ctx->t.p_barrett = use_barrett > 0 ? mpi_barrett_init(ctx->p, 0) : NULL;
+
+ mpi_ec_get_reset(ctx);
+
+ if (model == MPI_EC_MONTGOMERY) {
+ for (i = 0; i < DIM(bad_points_table); i++) {
+ MPI p_candidate = mpi_scanval(bad_points_table[i][0]);
+ int match_p = !mpi_cmp(ctx->p, p_candidate);
+ int j;
+
+ mpi_free(p_candidate);
+ if (!match_p)
+ continue;
+
+ for (j = 0; i < DIM(ctx->t.scratch) && bad_points_table[i][j]; j++)
+ ctx->t.scratch[j] = mpi_scanval(bad_points_table[i][j]);
+ }
+ } else {
+ /* Allocate scratch variables. */
+ for (i = 0; i < DIM(ctx->t.scratch); i++)
+ ctx->t.scratch[i] = mpi_alloc_like(ctx->p);
+ }
+
+ ctx->addm = ec_addm;
+ ctx->subm = ec_subm;
+ ctx->mulm = ec_mulm;
+ ctx->mul2 = ec_mul2;
+ ctx->pow2 = ec_pow2;
+
+ for (i = 0; field_table[i].p; i++) {
+ MPI f_p;
+
+ f_p = mpi_scanval(field_table[i].p);
+ if (!f_p)
+ break;
+
+ if (!mpi_cmp(p, f_p)) {
+ ctx->addm = field_table[i].addm;
+ ctx->subm = field_table[i].subm;
+ ctx->mulm = field_table[i].mulm;
+ ctx->mul2 = field_table[i].mul2;
+ ctx->pow2 = field_table[i].pow2;
+ mpi_free(f_p);
+
+ mpi_resize(ctx->a, ctx->p->nlimbs);
+ ctx->a->nlimbs = ctx->p->nlimbs;
+
+ mpi_resize(ctx->b, ctx->p->nlimbs);
+ ctx->b->nlimbs = ctx->p->nlimbs;
+
+ for (i = 0; i < DIM(ctx->t.scratch) && ctx->t.scratch[i]; i++)
+ ctx->t.scratch[i]->nlimbs = ctx->p->nlimbs;
+
+ break;
+ }
+
+ mpi_free(f_p);
+ }
+}
+EXPORT_SYMBOL_GPL(mpi_ec_init);
+
+void mpi_ec_deinit(struct mpi_ec_ctx *ctx)
+{
+ int i;
+
+ mpi_barrett_free(ctx->t.p_barrett);
+
+ /* Domain parameter. */
+ mpi_free(ctx->p);
+ mpi_free(ctx->a);
+ mpi_free(ctx->b);
+ mpi_point_release(ctx->G);
+ mpi_free(ctx->n);
+
+ /* The key. */
+ mpi_point_release(ctx->Q);
+ mpi_free(ctx->d);
+
+ /* Private data of ec.c. */
+ mpi_free(ctx->t.two_inv_p);
+
+ for (i = 0; i < DIM(ctx->t.scratch); i++)
+ mpi_free(ctx->t.scratch[i]);
+}
+EXPORT_SYMBOL_GPL(mpi_ec_deinit);
+
+/* Compute the affine coordinates from the projective coordinates in
+ * POINT. Set them into X and Y. If one coordinate is not required,
+ * X or Y may be passed as NULL. CTX is the usual context. Returns: 0
+ * on success or !0 if POINT is at infinity.
+ */
+int mpi_ec_get_affine(MPI x, MPI y, MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+ if (!mpi_cmp_ui(point->z, 0))
+ return -1;
+
+ switch (ctx->model) {
+ case MPI_EC_WEIERSTRASS: /* Using Jacobian coordinates. */
+ {
+ MPI z1, z2, z3;
+
+ z1 = mpi_new(0);
+ z2 = mpi_new(0);
+ ec_invm(z1, point->z, ctx); /* z1 = z^(-1) mod p */
+ ec_mulm(z2, z1, z1, ctx); /* z2 = z^(-2) mod p */
+
+ if (x)
+ ec_mulm(x, point->x, z2, ctx);
+
+ if (y) {
+ z3 = mpi_new(0);
+ ec_mulm(z3, z2, z1, ctx); /* z3 = z^(-3) mod p */
+ ec_mulm(y, point->y, z3, ctx);
+ mpi_free(z3);
+ }
+
+ mpi_free(z2);
+ mpi_free(z1);
+ }
+ return 0;
+
+ case MPI_EC_MONTGOMERY:
+ {
+ if (x)
+ mpi_set(x, point->x);
+
+ if (y) {
+ log_fatal("%s: Getting Y-coordinate on %s is not supported\n",
+ "mpi_ec_get_affine", "Montgomery");
+ return -1;
+ }
+ }
+ return 0;
+
+ case MPI_EC_EDWARDS:
+ {
+ MPI z;
+
+ z = mpi_new(0);
+ ec_invm(z, point->z, ctx);
+
+ mpi_resize(z, ctx->p->nlimbs);
+ z->nlimbs = ctx->p->nlimbs;
+
+ if (x) {
+ mpi_resize(x, ctx->p->nlimbs);
+ x->nlimbs = ctx->p->nlimbs;
+ ctx->mulm(x, point->x, z, ctx);
+ }
+ if (y) {
+ mpi_resize(y, ctx->p->nlimbs);
+ y->nlimbs = ctx->p->nlimbs;
+ ctx->mulm(y, point->y, z, ctx);
+ }
+
+ mpi_free(z);
+ }
+ return 0;
+
+ default:
+ return -1;
+ }
+}
+EXPORT_SYMBOL_GPL(mpi_ec_get_affine);
+
+/* RESULT = 2 * POINT (Weierstrass version). */
+static void dup_point_weierstrass(MPI_POINT result,
+ MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+#define x3 (result->x)
+#define y3 (result->y)
+#define z3 (result->z)
+#define t1 (ctx->t.scratch[0])
+#define t2 (ctx->t.scratch[1])
+#define t3 (ctx->t.scratch[2])
+#define l1 (ctx->t.scratch[3])
+#define l2 (ctx->t.scratch[4])
+#define l3 (ctx->t.scratch[5])
+
+ if (!mpi_cmp_ui(point->y, 0) || !mpi_cmp_ui(point->z, 0)) {
+ /* P_y == 0 || P_z == 0 => [1:1:0] */
+ mpi_set_ui(x3, 1);
+ mpi_set_ui(y3, 1);
+ mpi_set_ui(z3, 0);
+ } else {
+ if (ec_get_a_is_pminus3(ctx)) {
+ /* Use the faster case. */
+ /* L1 = 3(X - Z^2)(X + Z^2) */
+ /* T1: used for Z^2. */
+ /* T2: used for the right term. */
+ ec_pow2(t1, point->z, ctx);
+ ec_subm(l1, point->x, t1, ctx);
+ ec_mulm(l1, l1, mpi_const(MPI_C_THREE), ctx);
+ ec_addm(t2, point->x, t1, ctx);
+ ec_mulm(l1, l1, t2, ctx);
+ } else {
+ /* Standard case. */
+ /* L1 = 3X^2 + aZ^4 */
+ /* T1: used for aZ^4. */
+ ec_pow2(l1, point->x, ctx);
+ ec_mulm(l1, l1, mpi_const(MPI_C_THREE), ctx);
+ ec_powm(t1, point->z, mpi_const(MPI_C_FOUR), ctx);
+ ec_mulm(t1, t1, ctx->a, ctx);
+ ec_addm(l1, l1, t1, ctx);
+ }
+ /* Z3 = 2YZ */
+ ec_mulm(z3, point->y, point->z, ctx);
+ ec_mul2(z3, z3, ctx);
+
+ /* L2 = 4XY^2 */
+ /* T2: used for Y2; required later. */
+ ec_pow2(t2, point->y, ctx);
+ ec_mulm(l2, t2, point->x, ctx);
+ ec_mulm(l2, l2, mpi_const(MPI_C_FOUR), ctx);
+
+ /* X3 = L1^2 - 2L2 */
+ /* T1: used for L2^2. */
+ ec_pow2(x3, l1, ctx);
+ ec_mul2(t1, l2, ctx);
+ ec_subm(x3, x3, t1, ctx);
+
+ /* L3 = 8Y^4 */
+ /* T2: taken from above. */
+ ec_pow2(t2, t2, ctx);
+ ec_mulm(l3, t2, mpi_const(MPI_C_EIGHT), ctx);
+
+ /* Y3 = L1(L2 - X3) - L3 */
+ ec_subm(y3, l2, x3, ctx);
+ ec_mulm(y3, y3, l1, ctx);
+ ec_subm(y3, y3, l3, ctx);
+ }
+
+#undef x3
+#undef y3
+#undef z3
+#undef t1
+#undef t2
+#undef t3
+#undef l1
+#undef l2
+#undef l3
+}
+
+/* RESULT = 2 * POINT (Montgomery version). */
+static void dup_point_montgomery(MPI_POINT result,
+ MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+ (void)result;
+ (void)point;
+ (void)ctx;
+ log_fatal("%s: %s not yet supported\n",
+ "mpi_ec_dup_point", "Montgomery");
+}
+
+/* RESULT = 2 * POINT (Twisted Edwards version). */
+static void dup_point_edwards(MPI_POINT result,
+ MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+#define X1 (point->x)
+#define Y1 (point->y)
+#define Z1 (point->z)
+#define X3 (result->x)
+#define Y3 (result->y)
+#define Z3 (result->z)
+#define B (ctx->t.scratch[0])
+#define C (ctx->t.scratch[1])
+#define D (ctx->t.scratch[2])
+#define E (ctx->t.scratch[3])
+#define F (ctx->t.scratch[4])
+#define H (ctx->t.scratch[5])
+#define J (ctx->t.scratch[6])
+
+ /* Compute: (X_3 : Y_3 : Z_3) = 2( X_1 : Y_1 : Z_1 ) */
+
+ /* B = (X_1 + Y_1)^2 */
+ ctx->addm(B, X1, Y1, ctx);
+ ctx->pow2(B, B, ctx);
+
+ /* C = X_1^2 */
+ /* D = Y_1^2 */
+ ctx->pow2(C, X1, ctx);
+ ctx->pow2(D, Y1, ctx);
+
+ /* E = aC */
+ if (ctx->dialect == ECC_DIALECT_ED25519)
+ ctx->subm(E, ctx->p, C, ctx);
+ else
+ ctx->mulm(E, ctx->a, C, ctx);
+
+ /* F = E + D */
+ ctx->addm(F, E, D, ctx);
+
+ /* H = Z_1^2 */
+ ctx->pow2(H, Z1, ctx);
+
+ /* J = F - 2H */
+ ctx->mul2(J, H, ctx);
+ ctx->subm(J, F, J, ctx);
+
+ /* X_3 = (B - C - D) · J */
+ ctx->subm(X3, B, C, ctx);
+ ctx->subm(X3, X3, D, ctx);
+ ctx->mulm(X3, X3, J, ctx);
+
+ /* Y_3 = F · (E - D) */
+ ctx->subm(Y3, E, D, ctx);
+ ctx->mulm(Y3, Y3, F, ctx);
+
+ /* Z_3 = F · J */
+ ctx->mulm(Z3, F, J, ctx);
+
+#undef X1
+#undef Y1
+#undef Z1
+#undef X3
+#undef Y3
+#undef Z3
+#undef B
+#undef C
+#undef D
+#undef E
+#undef F
+#undef H
+#undef J
+}
+
+/* RESULT = 2 * POINT */
+static void
+mpi_ec_dup_point(MPI_POINT result, MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+ switch (ctx->model) {
+ case MPI_EC_WEIERSTRASS:
+ dup_point_weierstrass(result, point, ctx);
+ break;
+ case MPI_EC_MONTGOMERY:
+ dup_point_montgomery(result, point, ctx);
+ break;
+ case MPI_EC_EDWARDS:
+ dup_point_edwards(result, point, ctx);
+ break;
+ }
+}
+
+/* RESULT = P1 + P2 (Weierstrass version).*/
+static void add_points_weierstrass(MPI_POINT result,
+ MPI_POINT p1, MPI_POINT p2,
+ struct mpi_ec_ctx *ctx)
+{
+#define x1 (p1->x)
+#define y1 (p1->y)
+#define z1 (p1->z)
+#define x2 (p2->x)
+#define y2 (p2->y)
+#define z2 (p2->z)
+#define x3 (result->x)
+#define y3 (result->y)
+#define z3 (result->z)
+#define l1 (ctx->t.scratch[0])
+#define l2 (ctx->t.scratch[1])
+#define l3 (ctx->t.scratch[2])
+#define l4 (ctx->t.scratch[3])
+#define l5 (ctx->t.scratch[4])
+#define l6 (ctx->t.scratch[5])
+#define l7 (ctx->t.scratch[6])
+#define l8 (ctx->t.scratch[7])
+#define l9 (ctx->t.scratch[8])
+#define t1 (ctx->t.scratch[9])
+#define t2 (ctx->t.scratch[10])
+
+ if ((!mpi_cmp(x1, x2)) && (!mpi_cmp(y1, y2)) && (!mpi_cmp(z1, z2))) {
+ /* Same point; need to call the duplicate function. */
+ mpi_ec_dup_point(result, p1, ctx);
+ } else if (!mpi_cmp_ui(z1, 0)) {
+ /* P1 is at infinity. */
+ mpi_set(x3, p2->x);
+ mpi_set(y3, p2->y);
+ mpi_set(z3, p2->z);
+ } else if (!mpi_cmp_ui(z2, 0)) {
+ /* P2 is at infinity. */
+ mpi_set(x3, p1->x);
+ mpi_set(y3, p1->y);
+ mpi_set(z3, p1->z);
+ } else {
+ int z1_is_one = !mpi_cmp_ui(z1, 1);
+ int z2_is_one = !mpi_cmp_ui(z2, 1);
+
+ /* l1 = x1 z2^2 */
+ /* l2 = x2 z1^2 */
+ if (z2_is_one)
+ mpi_set(l1, x1);
+ else {
+ ec_pow2(l1, z2, ctx);
+ ec_mulm(l1, l1, x1, ctx);
+ }
+ if (z1_is_one)
+ mpi_set(l2, x2);
+ else {
+ ec_pow2(l2, z1, ctx);
+ ec_mulm(l2, l2, x2, ctx);
+ }
+ /* l3 = l1 - l2 */
+ ec_subm(l3, l1, l2, ctx);
+ /* l4 = y1 z2^3 */
+ ec_powm(l4, z2, mpi_const(MPI_C_THREE), ctx);
+ ec_mulm(l4, l4, y1, ctx);
+ /* l5 = y2 z1^3 */
+ ec_powm(l5, z1, mpi_const(MPI_C_THREE), ctx);
+ ec_mulm(l5, l5, y2, ctx);
+ /* l6 = l4 - l5 */
+ ec_subm(l6, l4, l5, ctx);
+
+ if (!mpi_cmp_ui(l3, 0)) {
+ if (!mpi_cmp_ui(l6, 0)) {
+ /* P1 and P2 are the same - use duplicate function. */
+ mpi_ec_dup_point(result, p1, ctx);
+ } else {
+ /* P1 is the inverse of P2. */
+ mpi_set_ui(x3, 1);
+ mpi_set_ui(y3, 1);
+ mpi_set_ui(z3, 0);
+ }
+ } else {
+ /* l7 = l1 + l2 */
+ ec_addm(l7, l1, l2, ctx);
+ /* l8 = l4 + l5 */
+ ec_addm(l8, l4, l5, ctx);
+ /* z3 = z1 z2 l3 */
+ ec_mulm(z3, z1, z2, ctx);
+ ec_mulm(z3, z3, l3, ctx);
+ /* x3 = l6^2 - l7 l3^2 */
+ ec_pow2(t1, l6, ctx);
+ ec_pow2(t2, l3, ctx);
+ ec_mulm(t2, t2, l7, ctx);
+ ec_subm(x3, t1, t2, ctx);
+ /* l9 = l7 l3^2 - 2 x3 */
+ ec_mul2(t1, x3, ctx);
+ ec_subm(l9, t2, t1, ctx);
+ /* y3 = (l9 l6 - l8 l3^3)/2 */
+ ec_mulm(l9, l9, l6, ctx);
+ ec_powm(t1, l3, mpi_const(MPI_C_THREE), ctx); /* fixme: Use saved value*/
+ ec_mulm(t1, t1, l8, ctx);
+ ec_subm(y3, l9, t1, ctx);
+ ec_mulm(y3, y3, ec_get_two_inv_p(ctx), ctx);
+ }
+ }
+
+#undef x1
+#undef y1
+#undef z1
+#undef x2
+#undef y2
+#undef z2
+#undef x3
+#undef y3
+#undef z3
+#undef l1
+#undef l2
+#undef l3
+#undef l4
+#undef l5
+#undef l6
+#undef l7
+#undef l8
+#undef l9
+#undef t1
+#undef t2
+}
+
+/* RESULT = P1 + P2 (Montgomery version).*/
+static void add_points_montgomery(MPI_POINT result,
+ MPI_POINT p1, MPI_POINT p2,
+ struct mpi_ec_ctx *ctx)
+{
+ (void)result;
+ (void)p1;
+ (void)p2;
+ (void)ctx;
+ log_fatal("%s: %s not yet supported\n",
+ "mpi_ec_add_points", "Montgomery");
+}
+
+/* RESULT = P1 + P2 (Twisted Edwards version).*/
+static void add_points_edwards(MPI_POINT result,
+ MPI_POINT p1, MPI_POINT p2,
+ struct mpi_ec_ctx *ctx)
+{
+#define X1 (p1->x)
+#define Y1 (p1->y)
+#define Z1 (p1->z)
+#define X2 (p2->x)
+#define Y2 (p2->y)
+#define Z2 (p2->z)
+#define X3 (result->x)
+#define Y3 (result->y)
+#define Z3 (result->z)
+#define A (ctx->t.scratch[0])
+#define B (ctx->t.scratch[1])
+#define C (ctx->t.scratch[2])
+#define D (ctx->t.scratch[3])
+#define E (ctx->t.scratch[4])
+#define F (ctx->t.scratch[5])
+#define G (ctx->t.scratch[6])
+#define tmp (ctx->t.scratch[7])
+
+ point_resize(result, ctx);
+
+ /* Compute: (X_3 : Y_3 : Z_3) = (X_1 : Y_1 : Z_1) + (X_2 : Y_2 : Z_3) */
+
+ /* A = Z1 · Z2 */
+ ctx->mulm(A, Z1, Z2, ctx);
+
+ /* B = A^2 */
+ ctx->pow2(B, A, ctx);
+
+ /* C = X1 · X2 */
+ ctx->mulm(C, X1, X2, ctx);
+
+ /* D = Y1 · Y2 */
+ ctx->mulm(D, Y1, Y2, ctx);
+
+ /* E = d · C · D */
+ ctx->mulm(E, ctx->b, C, ctx);
+ ctx->mulm(E, E, D, ctx);
+
+ /* F = B - E */
+ ctx->subm(F, B, E, ctx);
+
+ /* G = B + E */
+ ctx->addm(G, B, E, ctx);
+
+ /* X_3 = A · F · ((X_1 + Y_1) · (X_2 + Y_2) - C - D) */
+ ctx->addm(tmp, X1, Y1, ctx);
+ ctx->addm(X3, X2, Y2, ctx);
+ ctx->mulm(X3, X3, tmp, ctx);
+ ctx->subm(X3, X3, C, ctx);
+ ctx->subm(X3, X3, D, ctx);
+ ctx->mulm(X3, X3, F, ctx);
+ ctx->mulm(X3, X3, A, ctx);
+
+ /* Y_3 = A · G · (D - aC) */
+ if (ctx->dialect == ECC_DIALECT_ED25519) {
+ ctx->addm(Y3, D, C, ctx);
+ } else {
+ ctx->mulm(Y3, ctx->a, C, ctx);
+ ctx->subm(Y3, D, Y3, ctx);
+ }
+ ctx->mulm(Y3, Y3, G, ctx);
+ ctx->mulm(Y3, Y3, A, ctx);
+
+ /* Z_3 = F · G */
+ ctx->mulm(Z3, F, G, ctx);
+
+
+#undef X1
+#undef Y1
+#undef Z1
+#undef X2
+#undef Y2
+#undef Z2
+#undef X3
+#undef Y3
+#undef Z3
+#undef A
+#undef B
+#undef C
+#undef D
+#undef E
+#undef F
+#undef G
+#undef tmp
+}
+
+/* Compute a step of Montgomery Ladder (only use X and Z in the point).
+ * Inputs: P1, P2, and x-coordinate of DIF = P1 - P1.
+ * Outputs: PRD = 2 * P1 and SUM = P1 + P2.
+ */
+static void montgomery_ladder(MPI_POINT prd, MPI_POINT sum,
+ MPI_POINT p1, MPI_POINT p2, MPI dif_x,
+ struct mpi_ec_ctx *ctx)
+{
+ ctx->addm(sum->x, p2->x, p2->z, ctx);
+ ctx->subm(p2->z, p2->x, p2->z, ctx);
+ ctx->addm(prd->x, p1->x, p1->z, ctx);
+ ctx->subm(p1->z, p1->x, p1->z, ctx);
+ ctx->mulm(p2->x, p1->z, sum->x, ctx);
+ ctx->mulm(p2->z, prd->x, p2->z, ctx);
+ ctx->pow2(p1->x, prd->x, ctx);
+ ctx->pow2(p1->z, p1->z, ctx);
+ ctx->addm(sum->x, p2->x, p2->z, ctx);
+ ctx->subm(p2->z, p2->x, p2->z, ctx);
+ ctx->mulm(prd->x, p1->x, p1->z, ctx);
+ ctx->subm(p1->z, p1->x, p1->z, ctx);
+ ctx->pow2(sum->x, sum->x, ctx);
+ ctx->pow2(sum->z, p2->z, ctx);
+ ctx->mulm(prd->z, p1->z, ctx->a, ctx); /* CTX->A: (a-2)/4 */
+ ctx->mulm(sum->z, sum->z, dif_x, ctx);
+ ctx->addm(prd->z, p1->x, prd->z, ctx);
+ ctx->mulm(prd->z, prd->z, p1->z, ctx);
+}
+
+/* RESULT = P1 + P2 */
+void mpi_ec_add_points(MPI_POINT result,
+ MPI_POINT p1, MPI_POINT p2,
+ struct mpi_ec_ctx *ctx)
+{
+ switch (ctx->model) {
+ case MPI_EC_WEIERSTRASS:
+ add_points_weierstrass(result, p1, p2, ctx);
+ break;
+ case MPI_EC_MONTGOMERY:
+ add_points_montgomery(result, p1, p2, ctx);
+ break;
+ case MPI_EC_EDWARDS:
+ add_points_edwards(result, p1, p2, ctx);
+ break;
+ }
+}
+EXPORT_SYMBOL_GPL(mpi_ec_add_points);
+
+/* Scalar point multiplication - the main function for ECC. If takes
+ * an integer SCALAR and a POINT as well as the usual context CTX.
+ * RESULT will be set to the resulting point.
+ */
+void mpi_ec_mul_point(MPI_POINT result,
+ MPI scalar, MPI_POINT point,
+ struct mpi_ec_ctx *ctx)
+{
+ MPI x1, y1, z1, k, h, yy;
+ unsigned int i, loops;
+ struct gcry_mpi_point p1, p2, p1inv;
+
+ if (ctx->model == MPI_EC_EDWARDS) {
+ /* Simple left to right binary method. Algorithm 3.27 from
+ * {author={Hankerson, Darrel and Menezes, Alfred J. and Vanstone, Scott},
+ * title = {Guide to Elliptic Curve Cryptography},
+ * year = {2003}, isbn = {038795273X},
+ * url = {http://www.cacr.math.uwaterloo.ca/ecc/},
+ * publisher = {Springer-Verlag New York, Inc.}}
+ */
+ unsigned int nbits;
+ int j;
+
+ if (mpi_cmp(scalar, ctx->p) >= 0)
+ nbits = mpi_get_nbits(scalar);
+ else
+ nbits = mpi_get_nbits(ctx->p);
+
+ mpi_set_ui(result->x, 0);
+ mpi_set_ui(result->y, 1);
+ mpi_set_ui(result->z, 1);
+ point_resize(point, ctx);
+
+ point_resize(result, ctx);
+ point_resize(point, ctx);
+
+ for (j = nbits-1; j >= 0; j--) {
+ mpi_ec_dup_point(result, result, ctx);
+ if (mpi_test_bit(scalar, j))
+ mpi_ec_add_points(result, result, point, ctx);
+ }
+ return;
+ } else if (ctx->model == MPI_EC_MONTGOMERY) {
+ unsigned int nbits;
+ int j;
+ struct gcry_mpi_point p1_, p2_;
+ MPI_POINT q1, q2, prd, sum;
+ unsigned long sw;
+ mpi_size_t rsize;
+ int scalar_copied = 0;
+
+ /* Compute scalar point multiplication with Montgomery Ladder.
+ * Note that we don't use Y-coordinate in the points at all.
+ * RESULT->Y will be filled by zero.
+ */
+
+ nbits = mpi_get_nbits(scalar);
+ point_init(&p1);
+ point_init(&p2);
+ point_init(&p1_);
+ point_init(&p2_);
+ mpi_set_ui(p1.x, 1);
+ mpi_free(p2.x);
+ p2.x = mpi_copy(point->x);
+ mpi_set_ui(p2.z, 1);
+
+ point_resize(&p1, ctx);
+ point_resize(&p2, ctx);
+ point_resize(&p1_, ctx);
+ point_resize(&p2_, ctx);
+
+ mpi_resize(point->x, ctx->p->nlimbs);
+ point->x->nlimbs = ctx->p->nlimbs;
+
+ q1 = &p1;
+ q2 = &p2;
+ prd = &p1_;
+ sum = &p2_;
+
+ for (j = nbits-1; j >= 0; j--) {
+ MPI_POINT t;
+
+ sw = mpi_test_bit(scalar, j);
+ point_swap_cond(q1, q2, sw, ctx);
+ montgomery_ladder(prd, sum, q1, q2, point->x, ctx);
+ point_swap_cond(prd, sum, sw, ctx);
+ t = q1; q1 = prd; prd = t;
+ t = q2; q2 = sum; sum = t;
+ }
+
+ mpi_clear(result->y);
+ sw = (nbits & 1);
+ point_swap_cond(&p1, &p1_, sw, ctx);
+
+ rsize = p1.z->nlimbs;
+ MPN_NORMALIZE(p1.z->d, rsize);
+ if (rsize == 0) {
+ mpi_set_ui(result->x, 1);
+ mpi_set_ui(result->z, 0);
+ } else {
+ z1 = mpi_new(0);
+ ec_invm(z1, p1.z, ctx);
+ ec_mulm(result->x, p1.x, z1, ctx);
+ mpi_set_ui(result->z, 1);
+ mpi_free(z1);
+ }
+
+ point_free(&p1);
+ point_free(&p2);
+ point_free(&p1_);
+ point_free(&p2_);
+ if (scalar_copied)
+ mpi_free(scalar);
+ return;
+ }
+
+ x1 = mpi_alloc_like(ctx->p);
+ y1 = mpi_alloc_like(ctx->p);
+ h = mpi_alloc_like(ctx->p);
+ k = mpi_copy(scalar);
+ yy = mpi_copy(point->y);
+
+ if (mpi_has_sign(k)) {
+ k->sign = 0;
+ ec_invm(yy, yy, ctx);
+ }
+
+ if (!mpi_cmp_ui(point->z, 1)) {
+ mpi_set(x1, point->x);
+ mpi_set(y1, yy);
+ } else {
+ MPI z2, z3;
+
+ z2 = mpi_alloc_like(ctx->p);
+ z3 = mpi_alloc_like(ctx->p);
+ ec_mulm(z2, point->z, point->z, ctx);
+ ec_mulm(z3, point->z, z2, ctx);
+ ec_invm(z2, z2, ctx);
+ ec_mulm(x1, point->x, z2, ctx);
+ ec_invm(z3, z3, ctx);
+ ec_mulm(y1, yy, z3, ctx);
+ mpi_free(z2);
+ mpi_free(z3);
+ }
+ z1 = mpi_copy(mpi_const(MPI_C_ONE));
+
+ mpi_mul(h, k, mpi_const(MPI_C_THREE)); /* h = 3k */
+ loops = mpi_get_nbits(h);
+ if (loops < 2) {
+ /* If SCALAR is zero, the above mpi_mul sets H to zero and thus
+ * LOOPs will be zero. To avoid an underflow of I in the main
+ * loop we set LOOP to 2 and the result to (0,0,0).
+ */
+ loops = 2;
+ mpi_clear(result->x);
+ mpi_clear(result->y);
+ mpi_clear(result->z);
+ } else {
+ mpi_set(result->x, point->x);
+ mpi_set(result->y, yy);
+ mpi_set(result->z, point->z);
+ }
+ mpi_free(yy); yy = NULL;
+
+ p1.x = x1; x1 = NULL;
+ p1.y = y1; y1 = NULL;
+ p1.z = z1; z1 = NULL;
+ point_init(&p2);
+ point_init(&p1inv);
+
+ /* Invert point: y = p - y mod p */
+ point_set(&p1inv, &p1);
+ ec_subm(p1inv.y, ctx->p, p1inv.y, ctx);
+
+ for (i = loops-2; i > 0; i--) {
+ mpi_ec_dup_point(result, result, ctx);
+ if (mpi_test_bit(h, i) == 1 && mpi_test_bit(k, i) == 0) {
+ point_set(&p2, result);
+ mpi_ec_add_points(result, &p2, &p1, ctx);
+ }
+ if (mpi_test_bit(h, i) == 0 && mpi_test_bit(k, i) == 1) {
+ point_set(&p2, result);
+ mpi_ec_add_points(result, &p2, &p1inv, ctx);
+ }
+ }
+
+ point_free(&p1);
+ point_free(&p2);
+ point_free(&p1inv);
+ mpi_free(h);
+ mpi_free(k);
+}
+EXPORT_SYMBOL_GPL(mpi_ec_mul_point);
+
+/* Return true if POINT is on the curve described by CTX. */
+int mpi_ec_curve_point(MPI_POINT point, struct mpi_ec_ctx *ctx)
+{
+ int res = 0;
+ MPI x, y, w;
+
+ x = mpi_new(0);
+ y = mpi_new(0);
+ w = mpi_new(0);
+
+ /* Check that the point is in range. This needs to be done here and
+ * not after conversion to affine coordinates.
+ */
+ if (mpi_cmpabs(point->x, ctx->p) >= 0)
+ goto leave;
+ if (mpi_cmpabs(point->y, ctx->p) >= 0)
+ goto leave;
+ if (mpi_cmpabs(point->z, ctx->p) >= 0)
+ goto leave;
+
+ switch (ctx->model) {
+ case MPI_EC_WEIERSTRASS:
+ {
+ MPI xxx;
+
+ if (mpi_ec_get_affine(x, y, point, ctx))
+ goto leave;
+
+ xxx = mpi_new(0);
+
+ /* y^2 == x^3 + a·x + b */
+ ec_pow2(y, y, ctx);
+
+ ec_pow3(xxx, x, ctx);
+ ec_mulm(w, ctx->a, x, ctx);
+ ec_addm(w, w, ctx->b, ctx);
+ ec_addm(w, w, xxx, ctx);
+
+ if (!mpi_cmp(y, w))
+ res = 1;
+
+ mpi_free(xxx);
+ }
+ break;
+
+ case MPI_EC_MONTGOMERY:
+ {
+#define xx y
+ /* With Montgomery curve, only X-coordinate is valid. */
+ if (mpi_ec_get_affine(x, NULL, point, ctx))
+ goto leave;
+
+ /* The equation is: b * y^2 == x^3 + a · x^2 + x */
+ /* We check if right hand is quadratic residue or not by
+ * Euler's criterion.
+ */
+ /* CTX->A has (a-2)/4 and CTX->B has b^-1 */
+ ec_mulm(w, ctx->a, mpi_const(MPI_C_FOUR), ctx);
+ ec_addm(w, w, mpi_const(MPI_C_TWO), ctx);
+ ec_mulm(w, w, x, ctx);
+ ec_pow2(xx, x, ctx);
+ ec_addm(w, w, xx, ctx);
+ ec_addm(w, w, mpi_const(MPI_C_ONE), ctx);
+ ec_mulm(w, w, x, ctx);
+ ec_mulm(w, w, ctx->b, ctx);
+#undef xx
+ /* Compute Euler's criterion: w^(p-1)/2 */
+#define p_minus1 y
+ ec_subm(p_minus1, ctx->p, mpi_const(MPI_C_ONE), ctx);
+ mpi_rshift(p_minus1, p_minus1, 1);
+ ec_powm(w, w, p_minus1, ctx);
+
+ res = !mpi_cmp_ui(w, 1);
+#undef p_minus1
+ }
+ break;
+
+ case MPI_EC_EDWARDS:
+ {
+ if (mpi_ec_get_affine(x, y, point, ctx))
+ goto leave;
+
+ mpi_resize(w, ctx->p->nlimbs);
+ w->nlimbs = ctx->p->nlimbs;
+
+ /* a · x^2 + y^2 - 1 - b · x^2 · y^2 == 0 */
+ ctx->pow2(x, x, ctx);
+ ctx->pow2(y, y, ctx);
+ if (ctx->dialect == ECC_DIALECT_ED25519)
+ ctx->subm(w, ctx->p, x, ctx);
+ else
+ ctx->mulm(w, ctx->a, x, ctx);
+ ctx->addm(w, w, y, ctx);
+ ctx->mulm(x, x, y, ctx);
+ ctx->mulm(x, x, ctx->b, ctx);
+ ctx->subm(w, w, x, ctx);
+ if (!mpi_cmp_ui(w, 1))
+ res = 1;
+ }
+ break;
+ }
+
+leave:
+ mpi_free(w);
+ mpi_free(x);
+ mpi_free(y);
+
+ return res;
+}
+EXPORT_SYMBOL_GPL(mpi_ec_curve_point);
generated by cgit v1.2.3-58-ga151 (git 2.39.0) at 2024-11-25 07:19:37 +0000