A digital license includes an identification of a removal service that can authorize removing such license. A client selects the license to be removed and the service, constructs a challenge including therein a challenge license identification block (LIB) identifying the license to be removed, and sends...http://www.google.ca/patents/US8060923?utm_source=gb-gplus-sharePatent US8060923 - Trusted license removal in a content protection system or the like
