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Blinding RSA only active when f_rng is provided

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This commit is contained in:
Paul Bakker 2013-08-30 15:37:02 +02:00
parent 48377d9834
commit f451bac000
2 changed files with 31 additions and 27 deletions
library
rsa.c

44
library/rsa.c
View file

@ -267,8 +267,6 @@ int rsa_private( rsa_context *ctx,
mpi T, T1, T2;
mpi A, X;
if( f_rng == NULL )
return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
mpi_init( &T ); mpi_init( &T1 ); mpi_init( &T2 );
mpi_init( &A ); mpi_init( &X );
@ -283,15 +281,18 @@ int rsa_private( rsa_context *ctx,
#if defined(POLARSSL_RSA_NO_CRT)
MPI_CHK( mpi_exp_mod( &T, &T, &ctx->D, &ctx->N, &ctx->RN ) );
#else
/*
* RSA Blinding
* A = rnd MPI
* T = A^E * T mod N
*/
MPI_CHK( mpi_fill_random( &A, ctx->len - 1, f_rng, p_rng ) );
MPI_CHK( mpi_exp_mod( &X, &A, &ctx->E, &ctx->N, NULL ) );
MPI_CHK( mpi_mul_mpi( &X, &X, &T ) );
MPI_CHK( mpi_mod_mpi( &T, &X, &ctx->N ) );
if( f_rng != NULL )
{
/*
* RSA Blinding
* A = rnd MPI
* T = A^E * T mod N
*/
MPI_CHK( mpi_fill_random( &A, ctx->len - 1, f_rng, p_rng ) );
MPI_CHK( mpi_exp_mod( &X, &A, &ctx->E, &ctx->N, NULL ) );
MPI_CHK( mpi_mul_mpi( &X, &X, &T ) );
MPI_CHK( mpi_mod_mpi( &T, &X, &ctx->N ) );
}
/*
* faster decryption using the CRT
@ -310,18 +311,21 @@ int rsa_private( rsa_context *ctx,
MPI_CHK( mpi_mod_mpi( &T, &T1, &ctx->P ) );
/*
* X = T2 + T * Q
* T = T2 + T * Q
*/
MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->Q ) );
MPI_CHK( mpi_add_mpi( &X, &T2, &T1 ) );
MPI_CHK( mpi_add_mpi( &T, &T2, &T1 ) );
/*
* Unblind
* T = X / A mod N
*/
MPI_CHK( mpi_inv_mod( &A, &A, &ctx->N ) );
MPI_CHK( mpi_mul_mpi( &T, &X, &A ) );
MPI_CHK( mpi_mod_mpi( &T, &T, &ctx->N ) );
if( f_rng != NULL )
{
/*
* Unblind
* T = T / A mod N
*/
MPI_CHK( mpi_inv_mod( &A, &A, &ctx->N ) );
MPI_CHK( mpi_mul_mpi( &T, &T, &A ) );
MPI_CHK( mpi_mod_mpi( &T, &T, &ctx->N ) );
}
#endif
olen = ctx->len;