Patent ID: 7421082

Claim:
A digital data delivery method for use in delivering digital data from an upstream system to a downstream system, said upstream system providing multipoint delivery of encrypted digital data to specific destinations, and said downstream system decrypting the delivered digital data, said method comprising the steps of: encrypting digital data at said upstream system using an encryption key; generating on the basis of said encryption key, sets of passkeys, each set having at least two passkeys and each set of passkeys specific to a respective one of said specific destinations by dividing said encryption key by a division pattern that is: (a) unique to each of said specific destinations and (b) based on the content of said digital data; generating a plurality of partial keys based on a portion of the passkeys in said set or a portion of passkey information from which said passkeys may be reproduced; delivering either said plurality of partial keys or partial key information, from which said partial keys may be reproduced, and delivering the remaining passkeys in a set not used to generate said partial keys or the remaining passkey information, to a respective one of said specific destinations over a plurality of delivery routes which differ from routes for delivering said digital data and which are further different from each other; delivering the encrypted digital data; restoring said encryption key by using said downstream system using either said plurality of partial keys or said partial key information and using either said remaining passkeys or said remaining passkey information in a set delivered over said plurality of delivery routes; and using the restored encryption key to decrypt the encrypted digital data.