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.