Patent ID: 8893307

Claim:
An information processing system comprising: a content providing server that stores a plurality of copies of a content, each copy of the content stored while encrypted with a different encryption key; and a management server that transmits content selection information to a client device, the content selection information including range information and a set of encryption keys, wherein each copy of the content is divided into a plurality of content fragments, the range information includes information relating to beginning and end positions of each of the content fragments, each copy of the content having the same range information and the same beginning and end positions of each of the content fragments, the set of encryption keys includes a same number of encryption keys as a number of copies of the content stored by the content providing server, each encryption key of the set of encryption keys corresponding to a different copy of the content and used for the encryption and decryption of the corresponding copy of the content, the content providing server is configured to receive a content acquisition request from the client device, the content acquisition request including the range information and a copy identifier for a specific content fragment from a particular copy of the content, determine the specific content fragment from the particular copy of the content that corresponds to the range information and the copy identifier included in the content acquisition request, and transmit the specific fragment of content to the client device, and the copy identifier corresponds to a particular encryption key of the set of encryption keys provided in the content selection information for the range information in the transmitted content acquisition request.