Method and apparatus for establishing the legitimacy of use of a block of digitally represented information

Method and apparatus for establishing the legitimacy of use of a block of digitally represented information residing in a computer of a user. The block of digitally represented information may be a text file, a sound recording, a graphical file or a software file. The computer includes a program that processes the selected file to generate a substantially unique identification code. The code is transmitted to a server that contains a listing of files correlated to status data, indicative of whether the file is proprietary material and the conditions associated with its use. If the server locates an entry in its database it retrieves the status data and transmits it to the user's computer. In the event the identification code issued by the user's computer is not sufficiently discriminative, i.e., it does not allow the server to uniquely identify the file, the server transmits an algorithm identifier to the user's computer allowing the file to be re-processed with a new algorithm to generate a more distinctive identification code.