  Security against simple eavesdropping attacks is demonstrated for a recently
proposed quantum key distribution protocol which uses the Fibonacci recursion
relation to enable high-capacity key generation with entangled photon pairs. No
transmitted pairs need to be discarded in reconciliation; the only pairs not
used for key generation are those used for security-checking. Although the
proposed approach does not allow eavesdropper-induced errors to be detected on
single trials, it can nevertheless reveal the eavesdropper's action on the
quantum channel by detecting changes in the distribution of outcome
probabilities over multiple trials, and can do so as well as the BB84 protocol.
The mutual information shared by the participants is calculated and used to
show that a secret key can always be distilled.
