Reduce number of local MPIs from 9 to 4 in ecp_double_add_mxz()
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/ecp.c b/library/ecp.c
index cdffa1c..d63c571 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -2395,35 +2395,39 @@
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
#else
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
- mbedtls_mpi A, AA, B, BB, E, C, D, DA, CB;
- mbedtls_mpi_init( &A ); mbedtls_mpi_init( &AA ); mbedtls_mpi_init( &B );
- mbedtls_mpi_init( &BB ); mbedtls_mpi_init( &E ); mbedtls_mpi_init( &C );
- mbedtls_mpi_init( &D ); mbedtls_mpi_init( &DA ); mbedtls_mpi_init( &CB );
+ mbedtls_mpi T0,T1,T2,T3;
- MPI_ECP_ADD( &A, &P->X, &P->Z );
- MPI_ECP_SUB( &B, &P->X, &P->Z );
- MPI_ECP_ADD( &C, &Q->X, &Q->Z );
- MPI_ECP_SUB( &D, &Q->X, &Q->Z );
- MPI_ECP_MUL( &DA, &D, &A ); /* D no longer needed */
- MPI_ECP_MUL( &CB, &C, &B ); /* C no longer needed */
- MPI_ECP_SQR( &AA, &A ); /* A no longer needed */
- MPI_ECP_SQR( &BB, &B ); /* B no longer needed */
- MPI_ECP_MUL( &R->X, &AA, &BB );
- MPI_ECP_SUB( &E, &AA, &BB ); /* AA no longer needed */
- MPI_ECP_MUL( &R->Z, &grp->A, &E );
- MPI_ECP_ADD( &R->Z, &BB, &R->Z ); /* BB no longer needed */
- MPI_ECP_ADD( &S->X, &DA, &CB );
+ mbedtls_mpi_init( &T0 );
+ mbedtls_mpi_init( &T1 );
+ mbedtls_mpi_init( &T2 );
+ mbedtls_mpi_init( &T3 );
+
+ MPI_ECP_ADD( &T0, &P->X, &P->Z );
+ MPI_ECP_SUB( &T1, &P->X, &P->Z );
+ MPI_ECP_ADD( &T2, &Q->X, &Q->Z );
+ MPI_ECP_SUB( &T3, &Q->X, &Q->Z );
+ MPI_ECP_MUL( &T3, &T3, &T0 );
+ MPI_ECP_MUL( &T2, &T2, &T1 );
+ MPI_ECP_SQR( &T0, &T0 );
+ MPI_ECP_SQR( &T1, &T1 );
+ MPI_ECP_MUL( &R->X, &T0, &T1 );
+ MPI_ECP_SUB( &T0, &T0, &T1 );
+ MPI_ECP_MUL( &R->Z, &grp->A, &T0 );
+ MPI_ECP_ADD( &R->Z, &T1, &R->Z );
+ MPI_ECP_ADD( &S->X, &T3, &T2 );
MPI_ECP_SQR( &S->X, &S->X );
- MPI_ECP_SUB( &S->Z, &DA, &CB );
+ MPI_ECP_SUB( &S->Z, &T3, &T2 );
MPI_ECP_SQR( &S->Z, &S->Z );
MPI_ECP_MUL( &S->Z, d, &S->Z );
- MPI_ECP_MUL( &R->Z, &E, &R->Z );
+ MPI_ECP_MUL( &R->Z, &T0, &R->Z );
cleanup:
- mbedtls_mpi_free( &A ); mbedtls_mpi_free( &AA ); mbedtls_mpi_free( &B );
- mbedtls_mpi_free( &BB ); mbedtls_mpi_free( &E ); mbedtls_mpi_free( &C );
- mbedtls_mpi_free( &D ); mbedtls_mpi_free( &DA ); mbedtls_mpi_free( &CB );
+
+ mbedtls_mpi_free( &T0 );
+ mbedtls_mpi_free( &T1 );
+ mbedtls_mpi_free( &T2 );
+ mbedtls_mpi_free( &T3 );
return( ret );
#endif /* !defined(MBEDTLS_ECP_NO_FALLBACK) || !defined(MBEDTLS_ECP_DOUBLE_ADD_MXZ_ALT) */