We analyze the security of quantum cryptography schemes for d-level systems
using 2 or d+1 maximally conjugated bases, under individual eavesdropping
attacks based on cloning machines and measurement after the basis
reconciliation. We consider classical advantage distillation protocols, that
allow to extract a key even in situations where the mutual information between
the honest parties is smaller than the eavesdropper's information. In this
scenario, advantage distillation protocols are shown to be as powerful as
quantum distillation: key distillation is possible using classical techniques
if and only if the corresponding state in the entanglement based protocol is
distillable.Comment: 18 pages, 1 figure. Published versio
