Patent ID: 9015077
Filing Date: 2015-04-21
Classification: G06F,G06Q,H04L,Y10S

Abstract:
1. A decryption method comprising: decrypting by a computer a single-encrypted content key by using only a first key based on not having any devices with licenses for a predetermined content being revoked; decrypting by the computer a double-encrypted content key by using the first key and re-decrypting the decrypted content key by using a second key that prevents at least one revoked device from decrypting the predetermined content based on having at least one device among the devices with licenses for the predetermined content, being revoked; determining if the at least one device is revoked by referring to information included in a packet received from a server providing the predetermined content; and decrypting with the decrypted content key the predetermined content, wherein the decrypted content key is one of the single-decrypted content key and the double-decrypted content key, based on having said at least one revoked device among the devices with the licenses for the predetermined content, and wherein the content key is used to encrypt the predetermined content.