Dynamic varying of encrypting of a stream of data at an encryption unit based on data content is disclosed. The dynamic varying of the encrypting, which can be responsive to passage of a predefined number of units of physical data or passage of a predefined number of conceptual units of data, is accomplished by changing at least one encryption parameter over different portions of the data. The at least one encryption parameter can comprise one or more of an encryption key, an encryption granularity, an encryption density scale, an encryption density, an encryption delay, an encryption key update variable, and an encryption key update data trigger. The change in encryption parameter is signaled to a receiver's decryption unit and used by the decryption unit in decrypting the dynamically varied encrypted stream of data. The stream of data may comprise, e.g., MPEG compressed video or audio.
A method for a multi-path source routing in a sensor network. In the sensor network including a sink node and a plurality of sensor nodes, the sensor network transmits data packets through a downlink route set based on a routing table generated by collecting uplink neighbor information of each sensor node from a control message for initializing a network and an uplink route formed by using uplink neighbors of each sensor node. Uplink neighbors for transmitting data from each sensor node to the sink node by performing a network initialization process and acquires the information in the sink node to generate the multi-path is maintained. As a result, it has advantages of reducing a control message overhead while using the multi-path and increasing scalability and energy efficiency by keeping a routing table small in the sensor node regardless of the size of the network.
A resource allocation method and apparatus for an OFDMA-based mobile communication system that allows allocating resources of multiple carriers is provided. A Physical Downlink Control Channel (PDCCH) transmission method for allocating resources in multiple frequency bands of a mobile communication system based on an Orthogonal Frequency Division Multiple Access (OFDMA) according to the present invention includes generating and transmitting, at a base station, multiple PDCCHs for allocating resources in the multiple frequency bands using Control Channel Element (CCE) indices; and receiving and demodulating, at a user equipment, the multiple PDCCHs transmitted by the base station and locating the resources allocated in the multiple frequency bands using the CCE indices of respective PDCCHs. A Physical Downlink Control Channel (PDCCH) transmission apparatus for allocating resources in multiple frequency bands of a mobile communication system based on an Orthogonal Frequency Division Multiple Access (OFDMA) according to the present invention includes a base station apparatus which generates and transmits multiple PDCCHs for allocating resources in the multiple frequency bands using Control Channel Element (CCE) indices; and a user equipment which receives and demodulates the multiple PDCCHs transmitted by the base station and locates the resources allocated in the multiple frequency bands using the CCE indices of respective PDCCHs.