ID tag, tag reader, ID scrambling and descrambling methods, and tag manager

An ID tag for RF transmitting its own tag ID information is disclosed. The ID tag comprises an ID storage for outputting the tag ID information stored therein; an ID concealing unit that conceals the tag ID information based on a certain value relating to time and outputs a concealed ID; a time information concealing unit that conceals the certain value based on a stored tag unique value and outputs concealed information; and a data outputting unit that receives and combines the concealed ID and the concealed information, and outputs combined data.