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tune bignum.c

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This commit is contained in:
NIIBE Yutaka 2013-12-13 15:26:25 +09:00
parent cefdc0db0b
commit 78289257cf
2 changed files with 9 additions and 4 deletions
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6
ChangeLog
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@ -1,5 +1,11 @@
2013-12-13 Niibe Yutaka <gniibe@fsij.org>
* polarssl/library/bignum.c (mpi_exp_mod): Initialize lower
half of T with zero.
(mpi_montmul: Don't need to clear lower half of
T, as we keep zero. Call mpi_sub_hlp with upper half of T.
(mpi_montred): Ditto.
* polarssl/library/bignum.c (mpi_montmul, mpi_montred): Minimize
number of limbs for T.
(mpi_exp_mod): Only allocate N-n * 2 for T.

7
polarssl/library/bignum.c
View File

@ -1358,7 +1358,6 @@ static void mpi_montmul( mpi *A, const mpi *B, const mpi *N, t_uint mm, const mp
d = T->p;
n = N->n;
m = ( B->n < n ) ? B->n : n;
memset( d, 0, n * ciL );
for( i = 0; i < n; i++ )
{
@ -1380,7 +1379,7 @@ static void mpi_montmul( mpi *A, const mpi *B, const mpi *N, t_uint mm, const mp
mpi_sub_hlp( n, N->p, A->p );
else
/* prevent timing attacks */
mpi_sub_hlp( n, A->p, T->p );
mpi_sub_hlp( n, A->p, d);
}
/*
@ -1393,7 +1392,6 @@ static void mpi_montred( mpi *A, const mpi *N, t_uint mm, const mpi *T )
d = T->p;
n = N->n;
memset( d, 0, n * ciL );
for( i = 0; i < n; i++ )
{
@ -1421,7 +1419,7 @@ static void mpi_montred( mpi *A, const mpi *N, t_uint mm, const mpi *T )
mpi_sub_hlp( n, N->p, A->p );
else
/* prevent timing attacks */
mpi_sub_hlp( n, A->p, T->p );
mpi_sub_hlp( n, A->p, d);
}
/*
@ -1462,6 +1460,7 @@ int mpi_exp_mod( mpi *X, const mpi *A, const mpi *E, const mpi *N, mpi *_RR )
MPI_CHK( mpi_grow( X, j ) );
MPI_CHK( mpi_grow( &W[1], j ) );
MPI_CHK( mpi_grow( &T, j * 2 ) );
memset( T.p, 0, j * ciL ); /* Clear the lower half of T. */
/*
* Compensate for negative A (and correct at the end)