Abstract: The present invention discloses a network camera apparatus, network camera server and digital video recorder which makes it possible to prevent a digital image from being forged or altered by embedding a watermark into an image signal input through a camera in a real time. Two types of watermark, i.e. a robust watermark for authenticating whether the image is original image or not and a fragile watermark whether the image is forged or altered or where the forgery or alteration of image takes place. An authentication apparatus for authenticating the watermark-embedded image is further disclosed.

Abstract: A system for protecting copyright and content itself of digital contents generated with respect to their publication and distribution according to the means of wire/wireless communication, internet or off-line. First, digital contents inclusive of specific form of encrypted keys are received. A user compares such receipt with system information indicating characteristics of his/her unique system he/she is using, and when the compared information corresponds to each other, the digital contents are generated. The digital contents received in this regard are provided in a encrypted state according to the user's system information, and the digital contents are generated from extraction of decryption keys of the digital contents and from decryption of specific material among the digital contents. Accordingly, use only in the pertinent system is permitted so as to prevent illegal use of the contents.

Abstract: A digital information security system is disclosed. A user application tool installed in a user terminal, creates a unique user key using unique system information of the user terminal. A data storage unit stores user information and digital information. A user management tool installed in a server, receives the unique user key created by the user application tool, stores the received unique user key in the data storage unit as part of the user information, and compares, during user authentication, the stored unique user key with a unique user key provided from the user application tool of a user currently being subjected to authentication.