A system for generating authorization codes, such as personal
identification numbers, at the point of distribution of certificates of
value on which the authorization codes are to be printed or otherwise
encoded. Because the authorization codes are generated in real time, there
is no need to store and safeguard an inventory of preprinted certificates,
or even an inventory of activated authorization codes. The principles of
the invention apply both to systems for generating incentive award
certificates and to systems for generating purchased certificates of
value. The incentive awards or certificates of value are tokens of
prepayment for a service, such as long-distance telephone service or other
service. The authorization codes generated for inclusion with the value
certificates are unique and seemingly random. They are generated by taking
a non-random unique code, such as a sequence code, and encrypting it to
obtain seemingly random, but unique, authorization codes. Because each
authorization code is not generated until immediately prior to
distribution of the certificate with which the code is associated,
security and other problems pertaining to preprinted certificates and
cards are eliminated.