  The promise of secure cryptographic quantum key distribution schemes is based
on the use of quantum effects in the spin space. We point out that in fact in
many current quantum cryptography protocols the space part of the wave function
is neglected. However exactly the space part of the wave function describes the
behaviour of particles in ordinary real three-dimensional space. As a result
such schemes can be secure against eavesdropping attacks in the abstract spin
space but could be insecure in the real three-dimensional space. We discuss an
approach to the security of quantum key distribution in space by using Bell's
inequality and a special preparation of the space part of the wave function.
