add second ZKP (equality of two EC DLs) with test case

1 files changed, 49 insertions, 0 deletions

diff --git a/smc.c b/smc.c
index 52c1b3b..c58b1c2 100644
--- a/smc.c
+++ b/smc.c
@@ -45,8 +45,11 @@ smc_zkp_dl (gcry_mpi_point_t v, gcry_mpi_point_t g, gcry_mpi_t x,
 	gcry_mpi_t z = gcry_mpi_new (0);
 
 	brandt_ec_keypair_create_base (a, &z, g);
+
+	/* compute challange c */
 	/**TODO: generate c from HASH(g,v,a) and don't output it */
 	brandt_ec_skey_create (c);
+
 	*r = gcry_mpi_new (0);
 	gcry_mpi_mul (*r, *c, x);
 	gcry_mpi_add (*r, *r, z);
@@ -54,6 +57,7 @@ smc_zkp_dl (gcry_mpi_point_t v, gcry_mpi_point_t g, gcry_mpi_t x,
 	gcry_mpi_release (z);
 }
 
+
 /**
  * smc_zkp_dl_check
  *
@@ -84,6 +88,51 @@ smc_zkp_dl_check (gcry_mpi_point_t v, gcry_mpi_point_t g, gcry_mpi_point_t a,
 	return ret;
 }
 
+
+void
+smc_zkp_2dle (gcry_mpi_point_t v, gcry_mpi_point_t w, gcry_mpi_point_t g1, gcry_mpi_point_t g2, gcry_mpi_t x, gcry_mpi_point_t *a, gcry_mpi_point_t *b, gcry_mpi_t *c, gcry_mpi_t *r)
+{
+	gcry_mpi_t z = gcry_mpi_new (0);
+
+	brandt_ec_keypair_create_base (a, &z, g1);
+	*b = gcry_mpi_point_new(0);
+	gcry_mpi_ec_mul(*b, z, g2, ec_ctx);
+
+	/* compute challange c */
+	/**TODO: generate c from HASH(g1,g2,v,w,a,b) and don't output it */
+	brandt_ec_skey_create (c);
+
+	*r = gcry_mpi_new (0);
+	gcry_mpi_mul (*r, *c, x);
+	gcry_mpi_add (*r, *r, z);
+
+	gcry_mpi_release (z);
+}
+
+
+int
+smc_zkp_2dle_check (gcry_mpi_point_t v, gcry_mpi_point_t w, gcry_mpi_point_t g1, gcry_mpi_point_t g2, gcry_mpi_point_t a, gcry_mpi_point_t b, gcry_mpi_t c, gcry_mpi_t r)
+{
+	int              ret;
+	gcry_mpi_point_t left = gcry_mpi_point_new (0);
+	gcry_mpi_point_t right = gcry_mpi_point_new (0);
+
+	gcry_mpi_ec_mul (left, r, g1, ec_ctx);
+	gcry_mpi_ec_mul (right, c, v, ec_ctx);
+	gcry_mpi_ec_add (right, a, right, ec_ctx);
+	ret = brandt_ec_point_cmp (left, right);
+
+	gcry_mpi_ec_mul (left, r, g2, ec_ctx);
+	gcry_mpi_ec_mul (right, c, w, ec_ctx);
+	gcry_mpi_ec_add (right, b, right, ec_ctx);
+	ret &= brandt_ec_point_cmp (left, right);
+
+	gcry_mpi_point_release (left);
+	gcry_mpi_point_release (right);
+
+	return ret;
+}
+
 //GEN
 //smc_hextodec (const char *s)
 //{