From d9a3f47ecd803262a1c3b527afabc8b2b54e824e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= <mpg2@elzevir.fr>
Date: Tue, 11 Aug 2015 14:31:03 +0200
Subject: [PATCH] Add mbedtls_ecp_gen_keypair_base()

---
 include/mbedtls/ecp.h | 23 +++++++++++++++++++++++
 library/ecp.c         | 19 ++++++++++++++++---
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 723e46c98..e82704083 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -569,6 +569,29 @@ int mbedtls_ecp_check_pubkey( const mbedtls_ecp_group *grp, const mbedtls_ecp_po
  */
 int mbedtls_ecp_check_privkey( const mbedtls_ecp_group *grp, const mbedtls_mpi *d );
 
+/**
+ * \brief           Generate a keypair with configurable base point
+ *
+ * \param grp       ECP group
+ * \param G         Chosen base point
+ * \param d         Destination MPI (secret part)
+ * \param Q         Destination point (public part)
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successful,
+ *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
+ *
+ * \note            Uses bare components rather than an mbedtls_ecp_keypair structure
+ *                  in order to ease use with other structures such as
+ *                  mbedtls_ecdh_context of mbedtls_ecdsa_context.
+ */
+int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
+                     const mbedtls_ecp_point *G,
+                     mbedtls_mpi *d, mbedtls_ecp_point *Q,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
+
 /**
  * \brief           Generate a keypair
  *
diff --git a/library/ecp.c b/library/ecp.c
index 858540be2..b21e69d4f 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1761,9 +1761,11 @@ int mbedtls_ecp_check_privkey( const mbedtls_ecp_group *grp, const mbedtls_mpi *
 }
 
 /*
- * Generate a keypair
+ * Generate a keypair with configurable base point
  */
-int mbedtls_ecp_gen_keypair( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
+int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
+                     const mbedtls_ecp_point *G,
+                     mbedtls_mpi *d, mbedtls_ecp_point *Q,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng )
 {
@@ -1835,7 +1837,18 @@ cleanup:
     if( ret != 0 )
         return( ret );
 
-    return( mbedtls_ecp_mul( grp, Q, d, &grp->G, f_rng, p_rng ) );
+    return( mbedtls_ecp_mul( grp, Q, d, G, f_rng, p_rng ) );
+}
+
+/*
+ * Generate key pair, wrapper for conventional base point
+ */
+int mbedtls_ecp_gen_keypair( mbedtls_ecp_group *grp,
+                             mbedtls_mpi *d, mbedtls_ecp_point *Q,
+                             int (*f_rng)(void *, unsigned char *, size_t),
+                             void *p_rng )
+{
+    return( mbedtls_ecp_gen_keypair_base( grp, &grp->G, d, Q, f_rng, p_rng ) );
 }
 
 /*