Add ECDH primitives
diff --git a/include/polarssl/ecdh.h b/include/polarssl/ecdh.h
index 5c9be45..ad13106 100644
--- a/include/polarssl/ecdh.h
+++ b/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 @@
*/
int ecdh_self_test( int verbose );
+#ifdef __cplusplus
+}
+#endif
+
#endif
diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index e1b0995..b8b1997 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -147,12 +147,23 @@
/**
* \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
*
* \param P Destination point
diff --git a/library/ecdh.c b/library/ecdh.c
index a706b2e2..1515899 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -35,6 +35,45 @@
#include "polarssl/ecdh.h"
+/*
+ * Generate public key: simple wrapper around ecp_gen_keypair
+ */
+int ecdh_gen_public( const ecp_group *grp, mpi *d, ecp_point *Q,
+ int (*f_rng)(void *, unsigned char *, size_t),
+ void *p_rng )
+{
+ return ecp_gen_keypair( grp, d, Q, f_rng, p_rng );
+}
+
+/*
+ * Compute shared secret (SEC1 3.3.1)
+ */
+int ecdh_compute_shared( const ecp_group *grp, mpi *z,
+ const ecp_point *Q, const mpi *d )
+{
+ int ret;
+ ecp_point P;
+
+ ecp_point_init( &P );
+
+ /*
+ * Make sure Q is a valid pubkey before using it
+ */
+ MPI_CHK( ecp_check_pubkey( grp, Q ) );
+
+ MPI_CHK( ecp_mul( grp, &P, d, Q ) );
+
+ if( ecp_is_zero( &P ) )
+ return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
+
+ MPI_CHK( mpi_copy( z, &P.X ) );
+
+cleanup:
+ ecp_point_free( &P );
+
+ return( ret );
+}
+
#if defined(POLARSSL_SELF_TEST)
diff --git a/library/ecp.c b/library/ecp.c
index 9153f11..b8b0dfc 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -122,6 +122,14 @@
}
/*
+ * Tell if a point is zero
+ */
+int ecp_is_zero( ecp_point *pt )
+{
+ return( mpi_cmp_int( &pt->Z, 0 ) == 0 );
+}
+
+/*
* Copy the contents of Q into P
*/
int ecp_copy( ecp_point *P, const ecp_point *Q )