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Change ecp_mul() prototype to allow randomization

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(Also improve an error code while at it.)
This commit is contained in:
Manuel Pégourié-Gonnard 2013-09-02 14:29:09 +02:00
parent f451bac000
commit e09d2f8261
10 changed files with 99 additions and 37 deletions
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22
include/polarssl/ecp.h
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@ -411,17 +411,29 @@ int ecp_sub( const ecp_group *grp, ecp_point *R,
* \param R Destination point
* \param m Integer by which to multiply
* \param P Point to multiply
* \param f_rng RNG function (see notes)
* \param p_rng RNG parameter
*
* \return 0 if successful,
* POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed
* POLARSSL_ERR_ECP_GENERIC if m < 0 of m has greater bit
* length than N, the number of points in the group.
* 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 This function executes a constant number of operations
* for random m in the allowed range.
* \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 so such
* attack has been published yet.)
*/
int ecp_mul( const ecp_group *grp, ecp_point *R,
const mpi *m, const ecp_point *P );
const mpi *m, const ecp_point *P,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
/**
* \brief Check that a point is a valid public key on this curve