  We thoroughly analyse the novel quantum key distribution protocol introduced
recently in quant-ph/0412075, which is based on minimal qubit tomography. We
examine the efficiency of the protocol for a whole range of noise parameters
and present a general analysis of incoherent eavesdropping attacks with
arbitrarily many steps in the iterative key generation process. The comparison
with the tomographic 6-state protocol shows that our protocol has a higher
efficiency (up to 20%) and ensures the security of the established key even for
noise parameters far beyond the 6-state protocol's noise threshold.
