On the secrecy of a simple and effective implementation of BB84 quantum cryptography protocol

A simple and effective fiber implementation of the BB84 protocol is proposed, which does not use phase modulators at the receiving side and do not require adjustment of the polarization state at the output of the communication channel. The implementation of the protocol permits to prove of the secrecy of keys based on the fundamental entropic uncertainty relations. The secret key length is expressed only in terms of the values observed on the reception side, with various detector parameters, such as quantum efficiency and the probability of dark counts, are taken into account automatically for the secret key length, but implicitly in terms of the observed parameters.