An information processing system including a medium where a content to be played is stored; and a playing apparatus for playing a content stored in the medium; with the playing apparatus being configured to selectively activate a playing program according to a content type to be played, to obtain a device certificate correlated with the playing program from storage by executing the playing program, and to transmit the obtained device certificate to the medium; with the device certificate being a device certificate for content types in which content type information where the device certificate is available is recorded; and with the medium determining whether or not an encryption key with reading being requested from the playing apparatus is an encryption key for decrypting an encrypted content matching an available content type recorded in the device certificate, and permitting readout of the encryption key only in the case of matching.