Abstract: A multi-level data encryption and decryption system and a method thereof are provided. The method includes dividing a data into a plurality of sub-data blocks corresponding to a plurality of user levels. The method also includes generating an encryption key for each level according to a level generation key and a time key of the level and encrypting the sub-data block of each level by using the encryption key of the level, wherein the level generation key and the time key of a lower level are generated based on the same of an upper level, the time key is generated according to a time generation key and a time seed, and the time seed is periodically updated according to different encryption periods. Thereby, the number of keys to be managed by a user is reduced while the read rights of different users are managed with forward and backward data security.

Abstract: A method for transmitting buffer maps adapted in a peer-to-peer network comprising a plurality of peer nodes, and one or several super nodes are selected from the peer nodes, wherein when the buffer maps are transmitted in the peer-to-peer network, the super nodes are connected to each other, and each of the peer nodes is connected to one of the super nodes. First, each of the peer nodes transmits its buffer map to the super node connected thereto. Then, the super nodes exchanges the received buffer maps to each other, so as to synchronously update information of the buffer maps, and each of the super nodes updates a buffer map table recorded therein according to the exchanged buffer maps. Finally, each of the super nodes transmits the buffer map by the peer node connected thereto to the peer node.

Abstract: A remote assisting method is applied in a remote assisting system, which includes a server, a help-asking device and a helping device. The remote assisting method includes the following steps. First, ticket information is encrypted into encrypted ticket information, which is provided to the server, in response to a help-asking event and according to a first key. Next, the encrypted ticket information provided by the help-asking device is decoded into the ticket information according to a second key. Then, the ticket information, generated by decoding, is provided to the helping device such that the helping device can log in the help-asking device and perform a remote assisting operation.

Abstract: A multi-level data encryption and decryption system and a method thereof are provided. The method includes dividing a data into a plurality of sub-data blocks corresponding to a plurality of user levels. The method also includes generating an encryption key for each level according to a level generation key and a time key of the level and encrypting the sub-data block of each level by using the encryption key of the level, wherein the level generation key and the time key of a lower level are generated based on the same of an upper level, the time key is generated according to a time generation key and a time seed, and the time seed is periodically updated according to different encryption periods. Thereby, the number of keys to be managed by a user is reduced while the read rights of different users are managed with forward and backward data security.

Abstract: A hierarchical browsing management method and system for a digital content are described, in which a client decrypts a part of an encrypted content corresponding to an user permission of the client according to a different decryption key. The hierarchical browsing management method includes the following steps. A document fetching unit fetches a digital content, and then loads and stores the digital content to a document server. A client sends a request for transferring the digital content to another client to the document server. A key server executes a content encryption procedure, assigns a corresponding user permission to each content object, and generates encrypted objects. The content encryption procedure is executed to generate encrypted objects and a corresponding encrypted content according to the corresponding user permission assigned to each content object. The client receives the encrypted content, executes a decryption procedure for the encrypted objects, and outputs a decrypted content.