A method of securely providing data to a user's system over a broadcast infrastructure. The method comprising the steps of: encrypting the data using a first encrypting key; encrypting a first decrypting key using a second encrypting key; dividing at least part of the encrypted data into a series of...http://www.google.es/patents/US6834110?utm_source=gb-gplus-sharePatente US6834110 - Multi-tier digital TV programming for content distribution
Multi-tier digital TV programming for content distribution
