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Simplify DH blinding a bit

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This commit is contained in:
Manuel Pégourié-Gonnard 2013-09-04 16:39:03 +02:00
parent 143b5028a5
commit ed8a02bfae
3 changed files with 35 additions and 30 deletions
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55
library/dhm.c
View File

@ -257,37 +257,44 @@ static int dhm_update_blinding( dhm_context *ctx,
int ret, count; int ret, count;
/* /*
* We can just update the previous values (by squaring them) if: * If Vi is initialized, update it by squaring it
* - the values are initialized, and
* - our secret exponent did not change.
*/ */
if( ctx->Vi.p != NULL && if( ctx->Vi.p != NULL )
mpi_cmp_mpi( &ctx->X, &ctx->_X ) == 0 ) {
MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->P ) );
}
else
{
/* Vi = random( 2, P-1 ) */
count = 0;
do
{
mpi_fill_random( &ctx->Vi, mpi_size( &ctx->P ), f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->Vi, 1 );
if( count++ > 10 )
return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
}
while( mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
}
/*
* If X did not change, update Vf by squaring it too
*/
if( mpi_cmp_mpi( &ctx->X, &ctx->_X ) == 0 )
{ {
MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) ); MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) ); MPI_CHK( mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->P ) );
return( 0 ); return( 0 );
} }
/* /*
* Otherwise, we need to generate new values from scratch for this secret * Otherwise, compute Vf from scratch
*/ */
/* Vi = random( 2, P-1 ) */
count = 0;
do
{
mpi_fill_random( &ctx->Vi, mpi_size( &ctx->P ), f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->Vi, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->Vi, 1 );
if( count++ > 10 )
return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
}
while( mpi_cmp_int( &ctx->Vi, 1 ) <= 0 );
/* Vf = Vi^-X mod P */ /* Vf = Vi^-X mod P */
MPI_CHK( mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) ); MPI_CHK( mpi_inv_mod( &ctx->Vf, &ctx->Vi, &ctx->P ) );
MPI_CHK( mpi_exp_mod( &ctx->Vf, &ctx->Vf, &ctx->X, &ctx->P, &ctx->RP ) ); MPI_CHK( mpi_exp_mod( &ctx->Vf, &ctx->Vf, &ctx->X, &ctx->P, &ctx->RP ) );
@ -319,7 +326,7 @@ int dhm_calc_secret( dhm_context *ctx,
mpi_init( &GYb ); mpi_init( &GYb );
/* Blind peer's value */ /* Blind peer's value */
if( f_rng != 0 ) if( f_rng != NULL )
{ {
MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) ); MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
MPI_CHK( mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) ); MPI_CHK( mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
@ -333,7 +340,7 @@ int dhm_calc_secret( dhm_context *ctx,
&ctx->P, &ctx->RP ) ); &ctx->P, &ctx->RP ) );
/* Unblind secret value */ /* Unblind secret value */
if( f_rng != 0 ) if( f_rng != NULL )
{ {
MPI_CHK( mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) ); MPI_CHK( mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
MPI_CHK( mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) ); MPI_CHK( mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );

6
tests/suites/test_suite_dhm.data
View File

@ -1,8 +1,8 @@
Diffie-Hellman full exchange #1 Diffie-Hellman full exchange #1
dhm_do_dhm:1024:10:"23":10:"5" dhm_do_dhm:10:"23":10:"5"
Diffie-Hellman full exchange #2 Diffie-Hellman full exchange #2
dhm_do_dhm:1024:10:"93450983094850938450983409623":10:"9345098304850938450983409622" dhm_do_dhm:10:"93450983094850938450983409623":10:"9345098304850938450983409622"
Diffie-Hellman full exchange #3 Diffie-Hellman full exchange #3
dhm_do_dhm:1024:10:"93450983094850938450983409623982317398171298719873918739182739712938719287391879381271":10:"9345098309485093845098340962223981329819812792137312973297123912791271" dhm_do_dhm:10:"93450983094850938450983409623982317398171298719873918739182739712938719287391879381271":10:"9345098309485093845098340962223981329819812792137312973297123912791271"

4
tests/suites/test_suite_dhm.function
View File

@ -8,7 +8,7 @@
*/ */
/* BEGIN_CASE */ /* BEGIN_CASE */
void dhm_do_dhm( int NOTUSED, int radix_P, char *input_P, void dhm_do_dhm( int radix_P, char *input_P,
int radix_G, char *input_G ) int radix_G, char *input_G )
{ {
dhm_context ctx_srv; dhm_context ctx_srv;
@ -25,8 +25,6 @@ void dhm_do_dhm( int NOTUSED, int radix_P, char *input_P,
int x_size; int x_size;
rnd_pseudo_info rnd_info; rnd_pseudo_info rnd_info;
((void)NOTUSED);
memset( &ctx_srv, 0x00, sizeof( dhm_context ) ); memset( &ctx_srv, 0x00, sizeof( dhm_context ) );
memset( &ctx_cli, 0x00, sizeof( dhm_context ) ); memset( &ctx_cli, 0x00, sizeof( dhm_context ) );
memset( ske, 0x00, 1000 ); memset( ske, 0x00, 1000 );