The study of quantum cryptography and quantum non-locality have
traditionnally been based on two-level quantum systems (qubits). In this paper
we consider a generalisation of Ekert's cryptographic protocol [Ekert] where
qubits are replaced by qutrits. The security of this protocol is related to
non-locality, in analogy with Ekert's protocol. In order to study its
robustness against the optimal individual attacks, we derive the information
gained by a potential eavesdropper applying a cloning-based attack.Comment: 9 pages original version: july 2002, replaced in january 2003
(reason: minor changes
