diff options
Diffstat (limited to 'mpi/ec.c')
| -rw-r--r-- | mpi/ec.c | 67 |
1 files changed, 58 insertions, 9 deletions
@@ -337,6 +337,25 @@ ec_invm (gcry_mpi_t x, gcry_mpi_t a, mpi_ec_t ctx) } +/* Sync changed data in the context. */ +static void +ec_p_sync (mpi_ec_t ec) +{ + gcry_mpi_t tmp; + + if (!ec->t.need_sync) + return; + + 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); + + ec_invm (ec->t.two_inv_p, mpi_const (MPI_C_TWO), ec); + ec->t.need_sync = 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 @@ -345,20 +364,14 @@ static void ec_p_init (mpi_ec_t ctx, gcry_mpi_t p, gcry_mpi_t a) { int i; - gcry_mpi_t tmp; /* Fixme: Do we want to check some constraints? e.g. a < p */ ctx->p = mpi_copy (p); ctx->a = mpi_copy (a); - tmp = mpi_alloc_like (ctx->p); - mpi_sub_ui (tmp, ctx->p, 3); - ctx->t.a_is_pminus3 = !mpi_cmp (ctx->a, tmp); - mpi_free (tmp); - + ctx->t.need_sync = 1; ctx->t.two_inv_p = mpi_alloc (0); - ec_invm (ctx->t.two_inv_p, mpi_const (MPI_C_TWO), ctx); /* Allocate scratch variables. */ for (i=0; i< DIM(ctx->t.scratch); i++) @@ -492,10 +505,29 @@ _gcry_mpi_ec_get_mpi (const char *name, gcry_ctx_t ctx, int copy) return mpi_is_const (ec->n) && !copy? ec->n : mpi_copy (ec->n); if (!strcmp (name, "d") && ec->d) return mpi_is_const (ec->d) && !copy? ec->d : mpi_copy (ec->d); + + /* Return a requested point coordinate. */ if (!strcmp (name, "g.x") && ec->G && ec->G->x) return mpi_is_const (ec->G->x) && !copy? ec->G->x : mpi_copy (ec->G->x); if (!strcmp (name, "g.y") && ec->G && ec->G->y) return mpi_is_const (ec->G->y) && !copy? ec->G->y : mpi_copy (ec->G->y); + if (!strcmp (name, "q.x") && ec->Q && ec->Q->x) + return mpi_is_const (ec->Q->x) && !copy? ec->Q->x : mpi_copy (ec->Q->x); + if (!strcmp (name, "q.y") && ec->Q && ec->Q->y) + return mpi_is_const (ec->G->y) && !copy? ec->Q->y : mpi_copy (ec->Q->y); + + /* If a point has been requested, return it in standard encoding. */ + if (!strcmp (name, "g") && ec->G) + return _gcry_mpi_ec_ec2os (ec->G, ec); + if (!strcmp (name, "q")) + { + /* If only the private key is given, compute the public key. */ + if (!ec->Q && ec->d && ec->G && ec->p && ec->a) + _gcry_mpi_ec_mul_point (ec->Q, ec->d, ec->G, ec); + + if (ec->Q) + return _gcry_mpi_ec_ec2os (ec->Q, ec); + } return NULL; } @@ -510,8 +542,15 @@ _gcry_mpi_ec_get_point (const char *name, gcry_ctx_t ctx, int copy) if (!strcmp (name, "g") && ec->G) return point_copy (ec->G); - if (!strcmp (name, "q") && ec->Q) - return point_copy (ec->Q); + if (!strcmp (name, "q")) + { + /* If only the private key is given, compute the public key. */ + if (!ec->Q && ec->d && ec->G && ec->p && ec->a) + _gcry_mpi_ec_mul_point (ec->Q, ec->d, ec->G, ec); + + if (ec->Q) + return point_copy (ec->Q); + } return NULL; } @@ -527,11 +566,13 @@ _gcry_mpi_ec_set_mpi (const char *name, gcry_mpi_t newvalue, { mpi_free (ec->p); ec->p = mpi_copy (newvalue); + ec->t.need_sync = 1; } else if (!strcmp (name, "a")) { mpi_free (ec->a); ec->a = mpi_copy (newvalue); + ec->t.need_sync = 1; } else if (!strcmp (name, "b")) { @@ -628,6 +669,8 @@ _gcry_mpi_ec_dup_point (mpi_point_t result, mpi_point_t point, mpi_ec_t ctx) #define l2 (ctx->t.scratch[4]) #define l3 (ctx->t.scratch[5]) + ec_p_sync (ctx); + if (!mpi_cmp_ui (point->y, 0) || !mpi_cmp_ui (point->z, 0)) { /* P_y == 0 || P_z == 0 => [1:1:0] */ @@ -725,6 +768,8 @@ _gcry_mpi_ec_add_points (mpi_point_t result, #define t1 (ctx->t.scratch[9]) #define t2 (ctx->t.scratch[10]) + ec_p_sync (ctx); + if ( (!mpi_cmp (x1, x2)) && (!mpi_cmp (y1, y2)) && (!mpi_cmp (z1, z2)) ) { /* Same point; need to call the duplicate function. */ @@ -854,6 +899,8 @@ _gcry_mpi_ec_mul_point (mpi_point_t result, unsigned int nbits; int i; + ec_p_sync (ctx); + nbits = mpi_get_nbits (scalar); mpi_set_ui (result->x, 1); mpi_set_ui (result->y, 1); @@ -871,6 +918,8 @@ _gcry_mpi_ec_mul_point (mpi_point_t result, unsigned int i, loops; mpi_point_struct p1, p2, p1inv; + ec_p_sync (ctx); + x1 = mpi_alloc_like (ctx->p); y1 = mpi_alloc_like (ctx->p); h = mpi_alloc_like (ctx->p); |