  We report the security analysis of time-coding quantum key distribution
protocols. The protocols make use of coherent single-photon pulses. The key is
encoded in the photon time-detection. The use of coherent superposition of
states allows to detect eavesdropping of the key. We give a mathematical model
of a first protocol from which we derive a second, simpler, protocol. We derive
the security analysis of both protocols and find that the secure rates can be
similar to those obtained with the BB84 protocol. We then calculate the secure
distance for those protocols over standard fibre links. When using low-noise
superconducting single photon detectors, secure distances over 200 km can be
foreseen. Finally, we analyse the consequences of photon-number splitting
attacks when faint pulses are used instead of single photon pulses. A decoy
states technique can be used to prevent such attacks.
