Abstract: A method and apparatus are provided for simply and securely limiting a number of times that contents can be accessed using a hash chain. The apparatus limiting a number of times contents are accessed by a user terminal includes a hash chain generator receiving information indicating selected contents by the user terminal and information indicating how many times (n) the user terminal has authority to access the selected contents and generating a hash chain including n hash values derived from a seed value, and a contents access manager deleting the hash values one by one from the hash chain whenever the user terminal accesses the selected contents such that the number of times the contents can be accessed by the user terminal is decreased by the number of deleted hash values.

Abstract: A scrambling apparatus and method are provided for increasing randomness without damaging compression efficiency of total video data by selectively and randomly performing conversion when converting motion vector codes of compressed video data into other motion vector codes indicating other motion vector values, and more particularly, by performing conditional conversion only if a predetermined condition is satisfied when selective conversion of motion vector codes is performed. The scrambling apparatus includes a conversion motion vector code table generator generating a conversion motion vector code table comprising motion vector codes obtained by converting motion vector codes corresponding to motion vector values of input video data in a standard motion vector code table; and a conversion controller randomly determining whether a certain motion vector value is encoded using the conversion motion vector code table or the standard motion vector code table.

Abstract: A system and a method for allowing a plurality of devices interconnected for home networking to use the contents only by a single license without acquiring separate licenses for the devices. A transceiver module transmits/receives data to/from various devices. A license search module receives a request to issue a license from a home device through the transceiver module, searches for a corresponding formal license in a license storing module, and transmits the search result to both a license request module and a temporary license issuing module. The license request module requests the license server to issue the corresponding formal license when the formal license does not exist in the license storing module, and stores the license downloaded from the license server. The temporary license issuing module issues a temporary license to the corresponding home device through the transceiver module, based on the formal license stored in the license storing module.