Abstract: A key distribution scheme comprising a generation and reception system and a specific operation protocol is described. This system allows fast and secure key distribution in optical channels by two stations A and B. One or two true-random physical sources are used to generate random bits and a random sequence received provides the cipher to the following one to be sent. A starting shared secret key is used and the method can be described as a one-time-pad unlimited extender. The minimum probability of error in signal determination by an eavesdropper can be set arbitrarily close to the pure guessing level of one-half and the security of the method comes from the quantum noise of light as well as from the starting secret key. This system allows for optical amplification without security degradation within its operational boundaries.