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Tighten ecp_mul() validity checks

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Manuel Pégourié-Gonnard 2013-11-21 09:28:03 +01:00
parent 09ceaf49d0
commit ff27b7c968
4 changed files with 42 additions and 43 deletions
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15
include/polarssl/ecp.h
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@ -459,22 +459,19 @@ int ecp_sub( const ecp_group *grp, ecp_point *R,
* \param p_rng RNG parameter
*
* \return 0 if successful,
* POLARSSL_ERR_ECP_INVALID_KEY if m is not a valid privkey
* or P is not a valid pubkey,
* POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed
* POLARSSL_ERR_ECP_BAD_INPUT_DATA if m < 0 of m has greater
* bit length than N, the number of points in the group.
*
* \note In order to prevent simple timing attacks, this function
* executes a constant number of operations (that is, point
* doubling and addition of distinct points) for random m in
* the allowed range.
*
* \note If f_rng is not NULL, it is used to randomize projective
* coordinates of indermediate results, in order to prevent
* more elaborate timing attacks relying on intermediate
* operations. (This is a prophylactic measure since no such
* attack has been published yet.) Since this contermeasure
* has very low overhead, it is recommended to always provide
* a non-NULL f_rng parameter when using secret inputs.
* \note If f_rng is not NULL, it is used to randomize intermediate
* results in order to prevent potential attacks targetting
* these results. It is recommended to always provide a
* non-NULL f_rng (the overhead is negligible).
*/
int ecp_mul( ecp_group *grp, ecp_point *R,
const mpi *m, const ecp_point *P,