Rm ecp_add() and add ecp_muladd()
diff --git a/ChangeLog b/ChangeLog
index 28a3ef2..b6278a5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -61,7 +61,8 @@
Removals
* Removed mbedtls_ecp_group_read_string(). Only named groups are supported.
- * Removed mbedtls_ecp_sub().
+ * Removed mbedtls_ecp_sub() and mbedtls_ecp_add(), use
+ mbedtls_ecp_muladd().
* Removed individual mdX_hmac and shaX_hmac functions (use generic
md_hmac functions from md.h)
* Removed the PBKDF2 module (use PKCS5).
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 901c23e..224e135 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -482,26 +482,19 @@
unsigned char *buf, size_t blen );
/**
- * \brief Addition: R = P + Q
- *
- * \param grp ECP group
- * \param R Destination point
- * \param P Left-hand point
- * \param Q Right-hand point
- *
- * \return 0 if successful,
- * MBEDTLS_ERR_MPI_MALLOC_FAILED if memory allocation failed
- *
- * \note This function does not support Montgomery curves, such as
- * Curve25519.
- */
-int mbedtls_ecp_add( const mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
- const mbedtls_ecp_point *P, const mbedtls_ecp_point *Q );
-
-/**
* \brief Multiplication by an integer: R = m * P
* (Not thread-safe to use same group in multiple threads)
*
+ * \note In order to prevent timing attacks, this function
+ * executes the exact same sequence of (base field)
+ * operations for any valid m. It avoids any if-branch or
+ * array index depending on the value of m.
+ *
+ * \note If f_rng is not NULL, it is used to randomize intermediate
+ * results in order to prevent potential timing attacks
+ * targeting these results. It is recommended to always
+ * provide a non-NULL f_rng (the overhead is negligible).
+ *
* \param grp ECP group
* \param R Destination point
* \param m Integer by which to multiply
@@ -513,22 +506,36 @@
* MBEDTLS_ERR_ECP_INVALID_KEY if m is not a valid privkey
* or P is not a valid pubkey,
* MBEDTLS_ERR_MPI_MALLOC_FAILED if memory allocation failed
- *
- * \note In order to prevent timing attacks, this function
- * executes the exact same sequence of (base field)
- * operations for any valid m. It avoids any if-branch or
- * array index depending on the value of m.
- *
- * \note If f_rng is not NULL, it is used to randomize intermediate
- * results in order to prevent potential timing attacks
- * targeting these results. It is recommended to always
- * provide a non-NULL f_rng (the overhead is negligible).
*/
int mbedtls_ecp_mul( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
const mbedtls_mpi *m, const mbedtls_ecp_point *P,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
/**
+ * \brief Multiplication and addition of two points by integers:
+ * R = m * P + n * Q
+ * (Not thread-safe to use same group in multiple threads)
+ *
+ * \note In contrast to ecp_mul(), this function does not guarantee
+ * a constant execution flow and timing.
+ *
+ * \param grp ECP group
+ * \param R Destination point
+ * \param m Integer by which to multiply P
+ * \param P Point to multiply by m
+ * \param n Integer by which to multiply Q
+ * \param Q Point to be multiplied by n
+ *
+ * \return 0 if successful,
+ * MBEDTLS_ERR_ECP_INVALID_KEY if m or n is not a valid privkey
+ * or P or Q is not a valid pubkey,
+ * MBEDTLS_ERR_MPI_MALLOC_FAILED if memory allocation failed
+ */
+int mbedtls_ecp_muladd( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
+ const mbedtls_mpi *m, const mbedtls_ecp_point *P,
+ const mbedtls_mpi *n, const mbedtls_ecp_point *Q );
+
+/**
* \brief Check that a point is a valid public key on this curve
*
* \param grp Curve/group the point should belong to
diff --git a/library/ecdsa.c b/library/ecdsa.c
index a7dcddb..babc588 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -203,9 +203,9 @@
{
int ret;
mbedtls_mpi e, s_inv, u1, u2;
- mbedtls_ecp_point R, P;
+ mbedtls_ecp_point R;
- mbedtls_ecp_point_init( &R ); mbedtls_ecp_point_init( &P );
+ mbedtls_ecp_point_init( &R );
mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
/* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
@@ -249,9 +249,7 @@
* Since we're not using any secret data, no need to pass a RNG to
* mbedtls_ecp_mul() for countermesures.
*/
- MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &R, &u1, &grp->G, NULL, NULL ) );
- MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &P, &u2, Q, NULL, NULL ) );
- MBEDTLS_MPI_CHK( mbedtls_ecp_add( grp, &R, &R, &P ) );
+ MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) );
if( mbedtls_ecp_is_zero( &R ) )
{
@@ -275,7 +273,7 @@
}
cleanup:
- mbedtls_ecp_point_free( &R ); mbedtls_ecp_point_free( &P );
+ mbedtls_ecp_point_free( &R );
mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
return( ret );
diff --git a/library/ecp.c b/library/ecp.c
index f0fcc1f..52cedd3 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1049,24 +1049,6 @@
}
/*
- * Addition: R = P + Q, result's coordinates normalized
- */
-int mbedtls_ecp_add( const mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
- const mbedtls_ecp_point *P, const mbedtls_ecp_point *Q )
-{
- int ret;
-
- if( ecp_get_type( grp ) != ECP_TYPE_SHORT_WEIERSTRASS )
- return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
-
- MBEDTLS_MPI_CHK( ecp_add_mixed( grp, R, P, Q ) );
- MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
-
-cleanup:
- return( ret );
-}
-
-/*
* Randomize jacobian coordinates:
* (X, Y, Z) -> (l^2 X, l^3 Y, l Z) for random l
* This is sort of the reverse operation of ecp_normalize_jac().
@@ -1684,6 +1666,32 @@
}
#endif /* ECP_SHORTWEIERSTRASS */
+/*
+ * Linear combination
+ */
+int mbedtls_ecp_muladd( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
+ const mbedtls_mpi *m, const mbedtls_ecp_point *P,
+ const mbedtls_mpi *n, const mbedtls_ecp_point *Q )
+{
+ int ret;
+ mbedtls_ecp_point mP;
+
+ if( ecp_get_type( grp ) != ECP_TYPE_SHORT_WEIERSTRASS )
+ return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
+
+ mbedtls_ecp_point_init( &mP );
+
+ MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &mP, m, P, NULL, NULL ) );
+ MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, R, n, Q, NULL, NULL ) );
+ MBEDTLS_MPI_CHK( ecp_add_mixed( grp, R, &mP, R ) );
+ MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
+
+cleanup:
+ mbedtls_ecp_point_free( &mP );
+
+ return( ret );
+}
+
#if defined(ECP_MONTGOMERY)
/*
