Add ECDH primitives

include/polarssl/ecdh.h

@@ -33,9 +33,35 @@
 extern "C" {
 #endif
 
-#ifdef __cplusplus
-}
-#endif
+/**
+ * \brief           Generate a public key
+ *
+ * \param grp       ECP group
+ * \param d         Destination MPI (secret exponent)
+ * \param Q         Destination point (public key)
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successful,
+ *                  or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
+ */
+int ecdh_gen_public( const ecp_group *grp, mpi *d, ecp_point *Q,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
+
+/**
+ * \brief           Compute shared secret
+ *
+ * \param grp       ECP group
+ * \param z         Destination MPI (shared secret)
+ * \param Q         Public key from other party
+ * \param d         Our secret exponent
+ *
+ * \return          0 if successful,
+ *                  or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
+ */
+int ecdh_compute_shared( const ecp_group *grp, mpi *z,
+                         const ecp_point *Q, const mpi *d );
 
 /**
  * \brief          Checkup routine
@@ -44,4 +70,8 @@ extern "C" {
  */
 int ecdh_self_test( int verbose );
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif

include/polarssl/ecp.h

@@ -147,11 +147,22 @@ void ecp_group_free( ecp_group *grp );
 /**
  * \brief           Set a point to zero
  *
+ * \param pt        Destination point
+ *
  * \return          0 if successful,
  *                  POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed
  */
 int ecp_set_zero( ecp_point *pt );
 
+/**
+ * \brief           Tell if a point is zero
+ *
+ * \param pt        Point to test
+ *
+ * \return          1 if point is zero, 0 otherwise
+ */
+int ecp_is_zero( ecp_point *pt );
+
 /**
  * \brief           Copy the contents of point Q into P
  *