Patent ID: 8667272

Claim:
A content distribution method with broadcast encryption, comprising: executing once initially a setup process by a server presiding at the content distributor, the setup process produces a public key and one or more private keys; executing an encryption process by a server presiding at the content distributor, the encryption process comprising: computing once initially an initial ciphertext using the public key and a subscriber set; computing a new ciphertext when the subscriber set changes, the computation of the new ciphertext is based on a differential ciphertext generation method; generating an encryption secret; encrypting an original content into an encrypted content using the encryption secret; distributing the one or more private keys, the initial ciphertext or the new ciphertext, and the encrypted content to one or more content receiving clients in the distribution network; and executing a decryption process on the encrypted content by each of the content receiving clients in the distribution network, the decryption process is based on a wide window point addition method; wherein the subscriber set being a subset of all the content receiving clients in the distribution network decrypting the encrypted content into the original content using the private keys, and the initial ciphertext or the new ciphertext; wherein the subscriber set changes when one or more new subscribers are added to the subscriber set or one or more existing subscribers within the subscriber set are removed from the subscriber set; wherein the differential ciphertext generation method computes the new ciphertext by reusing previously preserved computational results of a previous ciphertext; and wherein the wide window point addition method reuses previously preserved computational results of group-divided point additions of public parameters in reconstructing the encryption secret.