A content assessment apparatus, content assessment method, information reproducing apparatus, and information recording medium are provided that can determine whether digital content has been processed abnormally. The information reproducing apparatus includes a drive (101) that reads content from an information recording medium (102) on which content including an electronic watermark, indicating an attribute denoting whether or not the content is encrypted, is recorded, a decryptor (103), a decryptor status monitor (104), a stream attribute monitor (106), a decision means (107) that determines that the content has been abnormally processed when a decryption status signal indicates otherwise than that decryption processing is being performed and an attribute detection signal indicates that the content is encrypted, or when the decryption status signal indicates that decryption processing is being performed and the attribute detection signal indicates that the content is non-encrypted, a video decoder (105), and an output control means (108) that is not allowed to output the video signal if the content has been abnormally processed.