Abstract: A method and system for achieving the cryptographic objectives of data encryption and/or key expansion/generation by utilizing a short, shared, secret seed key between two parties that is extended to a long extended key which, in turn, is used to select one of many possible quantum and/or classical signal sets. The signal strength of each signal in the signal set is adjusted in accordance with the number of signal sets to obtain the necessary security level. The system operates with whatever signal quantum noise and other system noises are present while preserving security of the cryptographic system. The signal quantum noise and system noises protect both the data and the key from attackers.

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.