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Add Montgomery points to ecp_point_read_binary

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The library is able to perform computations and cryptographic schemes on
curves with x coordinate ladder representation. Here we add the
capability to import such points.
This commit is contained in:
Janos Follath
2019-02-13 10:44:06 +00:00
parent a778a94b7d
commit 59b813c7be
3 changed files with 65 additions and 17 deletions
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51
library/ecp.c
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@ -788,7 +788,7 @@ cleanup:
}
/*
* Import a point from unsigned binary data (SEC1 2.3.4)
* Import a point from unsigned binary data (SEC1 2.3.4 and RFC7748)
*/
int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *pt,
@ -803,24 +803,45 @@ int mbedtls_ecp_point_read_binary( const mbedtls_ecp_group *grp,
if( ilen < 1 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
if( buf[0] == 0x00 )
{
if( ilen == 1 )
return( mbedtls_ecp_set_zero( pt ) );
else
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
}
plen = mbedtls_mpi_size( &grp->P );
if( buf[0] != 0x04 )
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
#if defined(ECP_MONTGOMERY)
if( ecp_get_type( grp ) == ECP_TYPE_MONTGOMERY )
{
if( plen != ilen )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
if( ilen != 2 * plen + 1 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary_le( &pt->X, buf, plen ) );
mbedtls_mpi_free( &pt->Y );
if( grp->id == MBEDTLS_ECP_DP_CURVE25519 )
/* Set most significant bit to 0 */
MBEDTLS_MPI_CHK( mbedtls_mpi_set_bit( &pt->X, plen * 8 - 1, 0 ) );
}
#endif
#if defined(ECP_SHORTWEIERSTRASS)
if( ecp_get_type( grp ) != ECP_TYPE_MONTGOMERY )
{
if( buf[0] == 0x00 )
{
if( ilen == 1 )
return( mbedtls_ecp_set_zero( pt ) );
else
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
}
if( buf[0] != 0x04 )
return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
if( ilen != 2 * plen + 1 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->X, buf + 1, plen ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->Y,
buf + 1 + plen, plen ) );
}
#endif
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->X, buf + 1, plen ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &pt->Y, buf + 1 + plen, plen ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &pt->Z, 1 ) );
cleanup: