A system for providing the right to use and reproduce contents data involving so-called electronic money, whereby when compressed and/or encrypted contents data is reproduced, a security for electronic money or an electronic use right is checked, if the electronic money or the electronic use right is invalid as a result of the security check, the reproduction of the contents data is stopped, and if the electronic money or the electronic use right is valid as a result of the security check, the contents data is reproduced and the electronic money or the electronic use right is consumed.