/*
* Create own private value X and export G^X
*/
int dhm_make_public( dhm_context *ctx, int x_size,
unsigned char *output, size_t olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, n;
if( ctx == NULL || olen < 1 || olen > ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
/*
* generate X and calculate GX = G^X mod P
*/
n = x_size / sizeof( t_uint ) + 1;
mpi_fill_random( &ctx->X, n, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
MPI_CHK( mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED + ret );
return( 0 );
}
/*
* Generate or update blinding values, see section 10 of:
* KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA,
* DSS, and other systems. In : Advances in Cryptology—CRYPTO’96. Springer
* Berlin Heidelberg, 1996. p. 104-113.
*/
static int rsa_prepare_blinding( rsa_context *ctx,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret;
if( ctx->Vf.p != NULL )
{
/* We already have blinding values, just update them by squaring */
MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
MPI_CHK( mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->N ) );
return( 0 );
}
/* Unblinding value: Vf = random number */
MPI_CHK( mpi_fill_random( &ctx->Vf, ctx->len - 1, f_rng, p_rng ) );
/* Mathematically speaking, the algorithm should check Vf
* against 0, P and Q (Vf should be relatively prime to N, and 0 < Vf < N),
* so that Vf^-1 exists.
*/
/* Blinding value: Vi = Vf^(-e) mod N */
MPI_CHK( mpi_inv_mod( &ctx->Vi, &ctx->Vf, &ctx->N ) );
MPI_CHK( mpi_exp_mod( &ctx->Vi, &ctx->Vi, &ctx->E, &ctx->N, &ctx->RN ) );
cleanup:
return( ret );
}
/*
* Setup and write the ServerKeyExchange parameters
*/
int dhm_make_params( dhm_context *ctx, int x_size,
unsigned char *output, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, n;
size_t n1, n2, n3;
unsigned char *p;
/*
* Generate X as large as possible ( < P )
*/
n = x_size / sizeof( t_uint ) + 1;
mpi_fill_random( &ctx->X, n, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
/*
* Calculate GX = G^X mod P
*/
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
/*
* export P, G, GX
*/
#define DHM_MPI_EXPORT(X,n) \
MPI_CHK( mpi_write_binary( X, p + 2, n ) ); \
*p++ = (unsigned char)( n >> 8 ); \
*p++ = (unsigned char)( n ); p += n;
n1 = mpi_size( &ctx->P );
n2 = mpi_size( &ctx->G );
n3 = mpi_size( &ctx->GX );
p = output;
DHM_MPI_EXPORT( &ctx->P , n1 );
DHM_MPI_EXPORT( &ctx->G , n2 );
DHM_MPI_EXPORT( &ctx->GX, n3 );
*olen = p - output;
ctx->len = n1;
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );
return( 0 );
}
/*
* Generate or update blinding values, see section 10 of:
* KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA,
* DSS, and other systems. In : Advances in Cryptology—CRYPTO’96. Springer
* Berlin Heidelberg, 1996. p. 104-113.
*/
static int rsa_prepare_blinding( rsa_context *ctx, mpi *Vi, mpi *Vf,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret, count = 0;
#if defined(POLARSSL_THREADING_C)
polarssl_mutex_lock( &ctx->mutex );
#endif
if( ctx->Vf.p != NULL )
{
/* We already have blinding values, just update them by squaring */
MPI_CHK( mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &ctx->Vi ) );
MPI_CHK( mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
MPI_CHK( mpi_mul_mpi( &ctx->Vf, &ctx->Vf, &ctx->Vf ) );
MPI_CHK( mpi_mod_mpi( &ctx->Vf, &ctx->Vf, &ctx->N ) );
goto done;
}
/* Unblinding value: Vf = random number, invertible mod N */
do {
if( count++ > 10 )
return( POLARSSL_ERR_RSA_RNG_FAILED );
MPI_CHK( mpi_fill_random( &ctx->Vf, ctx->len - 1, f_rng, p_rng ) );
MPI_CHK( mpi_gcd( &ctx->Vi, &ctx->Vf, &ctx->N ) );
} while( mpi_cmp_int( &ctx->Vi, 1 ) != 0 );
/* Blinding value: Vi = Vf^(-e) mod N */
MPI_CHK( mpi_inv_mod( &ctx->Vi, &ctx->Vf, &ctx->N ) );
MPI_CHK( mpi_exp_mod( &ctx->Vi, &ctx->Vi, &ctx->E, &ctx->N, &ctx->RN ) );
done:
if( Vi != &ctx->Vi )
{
MPI_CHK( mpi_copy( Vi, &ctx->Vi ) );
MPI_CHK( mpi_copy( Vf, &ctx->Vf ) );
}
cleanup:
#if defined(POLARSSL_THREADING_C)
polarssl_mutex_unlock( &ctx->mutex );
#endif
return( ret );
}
