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Support brainpool curves in ecp_check_pubkey()

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Manuel Pégourié-Gonnard
2013-10-08 13:11:30 +02:00
parent 43545c8b4f
commit cd7458aafd
2 changed files with 32 additions and 21 deletions
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20
library/ecp.c
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@ -1608,13 +1608,21 @@ int ecp_check_pubkey( const ecp_group *grp, const ecp_point *pt )
/*
* YY = Y^2
* RHS = X (X^2 - 3) + B = X^3 - 3X + B
* RHS = X (X^2 + A) + B = X^3 + A X + B
* with, as usual, A = -3 if A is ommited
*/
MPI_CHK( mpi_mul_mpi( &YY, &pt->Y, &pt->Y ) ); MOD_MUL( YY );
MPI_CHK( mpi_mul_mpi( &RHS, &pt->X, &pt->X ) ); MOD_MUL( RHS );
MPI_CHK( mpi_sub_int( &RHS, &RHS, 3 ) ); MOD_SUB( RHS );
MPI_CHK( mpi_mul_mpi( &RHS, &RHS, &pt->X ) ); MOD_MUL( RHS );
MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->B ) ); MOD_ADD( RHS );
MPI_CHK( mpi_mul_mpi( &YY, &pt->Y, &pt->Y ) ); MOD_MUL( YY );
MPI_CHK( mpi_mul_mpi( &RHS, &pt->X, &pt->X ) ); MOD_MUL( RHS );
if( grp->A.p == NULL )
{
MPI_CHK( mpi_add_int( &RHS, &RHS, -3 ) ); MOD_SUB( RHS );
}
else
{
MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->A ) ); MOD_ADD( RHS );
}
MPI_CHK( mpi_mul_mpi( &RHS, &RHS, &pt->X ) ); MOD_MUL( RHS );
MPI_CHK( mpi_add_mpi( &RHS, &RHS, &grp->B ) ); MOD_ADD( RHS );
if( mpi_cmp_mpi( &YY, &RHS ) != 0 )
ret = POLARSSL_ERR_ECP_INVALID_KEY;