Abstract: An apparatus and method for video watermarking are provided. The apparatus and method include receiving a bit stream encoded by a video encoder by a spatial domain information analyzer and extracting information from a spatial domain of an image with respect to code words forming the bit stream, grouping the code words for each segmented domain by a domain classifier based on the information from the spatial domain, determining a sign of the each segmented domain by a domain sign determiner and inserting a watermark in the each segmented domain according to the sign determined by the domain sign determiner by a watermark bit inserter.

Abstract: A key update method and a key update apparatus are provided. The method includes storing data in a database of an update server, the data having an encoded updated node key in response to a node key update for a group; selecting necessary data, from among the data having the encoded updated node key, to calculate a key immediately prior to when the member is switched to the online mode, and generating member update data; and performing a key update with respect to the member using the member update data in a device corresponding to the member which has switched from the offline mode to the online mode.

Abstract: A method and a system for managing a key of a home device in a broadcast encryption system are provided. A hierarchical structure of a group set comprising a plurality of nodes corresponding to the home server and a plurality of nodes corresponding to the home device is formed. A key set to be allotted to the node set is generated. The node group is allowed to correspond to the key set to generate key-node corresponding information according to a request of the home server.

Abstract: A tag generation method for generating tags used in data packets in a broadcast encryption system is provided. The method includes detecting at least one revoked leaf node; setting a node identification (node ID) assigned to at least one node among nodes assigned node IDs at a layer 0 and to which the at least one revoked leaf node is subordinate, to a node path identification (NPID) of the at least one revoked leaf node at the layer 0; generating a tag list in the layer 0 by combining the NPID of each of the at least one revoked leaf nodes at the layer 0 in order of increment of node IDs of the corresponding at least one revoked leaf nodes; and generating a tag list in a lowest layer by repeatedly performing the setting and generation operation down to the lowest layer.

Abstract: A hierarchical threshold tree-based broadcast encryption method includes a first step for a server initialization and a user subscription, a second step of distributing a message to enable a privileged user (authorized user) to decrypt a group key, and a third step of the privileged user (authorized user) decrypting the message using the group key. According to the method, it is possible to prevent any group of revocators from obtaining the group key using their secret information and information being broadcast by the server.

Abstract: Provided is an apparatus and method of a portable terminal authenticating another portable terminal. The portable terminal may receive a seed generated by the other portable terminal, issue an authentication certificate generated using the seed to the other portable terminal, authenticate the other portable terminal based on the authentication certificate, and provide a secure communication.

Abstract: A radio frequency system and a password management method applied to a storage device of the radio frequency system are provided, in which a first access password is stored for deciding whether to permit access to information and a first changed password. The first changed password, a second access password, and a second changed password are received, and the first access password is changed to the second access password, and the first changed password is changed to the second changed password. Accordingly, information access authority in the storage device and a password change authority can be exclusively transferred according to the transfer of management of the storage device, and information leakage caused by a previous manager's password leakage or a third person's password leakage can be prevented.

Abstract: A user key management method for a broadcast encryption includes assigning node path identifiers (IDs) to nodes arranged in sequence; assigning random seed value keys to the nodes according to the node path IDs; generating key values by repeatedly applying a hash function to the assigned random seed value keys; and assigning the generated key values to the nodes in sequence. Accordingly, it is possible to reduce the transmission overhead that is most important matter in the broadcast encryption to less than the number of the revoked users. Further, there is an advantage that the transmission overhead of the exemplary embodiments of the present invention is remarkably reduced compared with the Subset Difference method.

Abstract: A video fingerprint insertion apparatus is provided. A frequency domain selection unit selects a frequency domain into which a fingerprint is inserted, from frequency domains of a video; a fingerprint insertion position determination unit determines a position where the fingerprint is to be inserted, based on a fingerprint insertion determination value in the selected frequency domain; and a fingerprint insertion unit inserts a fingerprint bit stream whose insertion strength is controlled, to the position where the fingerprint is to be inserted.

Abstract: Provided is an apparatus to transmit and receive data, and a method thereof. A data transmission apparatus may generate a first cryptogram and a second cryptogram by encrypting a message authentication code to be transmitted, using a plurality of encryption keys, and may transmit the generated first cryptogram and the second cryptogram to a data reception apparatus.

Abstract: A hybrid broadcast encryption method is provided. The hybrid broadcast encryption method includes setting initialization values, generating a node secret using the initialization values; generating a private secret using the node secret; sending the node secret and the private secret; generating a broadcast message based on a revoked group; encrypting a session key using a key encryption key (KEK) which is allocated to every user group and the broadcast message; and broadcasting to every user the encrypted session key and the broadcast message.

Abstract: A security device and a head end of a conditional access system (CAS), and a method for controlling illegal use of the conditional access system, capable of minimizing the number of entitlement management messages (EMMs) to be distributed from a head end to a user are provided. Update keys encrypted with user keys and channel management keys encrypted with the update keys are utilized.

Abstract: A security method using an electronic signature, which improves the performance of an electronic signature authentication by generating and verifying an electronic signature using a mediator, and acquires a forward security in an electronic signature generation and verification by adding a forward secure signature of semi-trusted party (SEM) to a partial signature value generated based on a secret key piece of the SEM. A public key and an optional secret key composed of two kinds of pieces are generated by a certificate authority in response to a request from a user terminal device. The secret key pieces are issued to the user terminal device and a semi-trusted party not to be overlapped with each other. A first signature piece generated from the issued pieces of the private key is transmitted to the user terminal device from the semi-trusted party when a certificate of the user terminal device is still valid.

Abstract: A radio frequency identification (RFID) tag encryption method and system using a broadcast encryption (BE) scheme are provided by encrypting an ID of an RFID tag, storing the encrypted ID in a server and the RFID tag, and storing information relating to a reader authorized to read out the RFID tag in the server so that the reader can read out the RFID tag by decrypting the encrypted ID based on the encrypted ID information read from the RFID tag and the reader information. When readers read out ID data from the RFID tag, a privileged reader can read the data. Thus, it is possible to block unintended information leakage to the readers. In addition, user usability can be enhanced since an attacker cannot perform an access lock on the RFID tag.

Abstract: A radio frequency identification (RFID) tag, an RFID privacy protection system, and an RFID privacy protection method are provided. The RFID privacy protection method includes a pseudo identification (ID) used to authenticate the RFID reader and a key used to generate the pseudo ID are received; if the pseudo ID is received in response to an information request signal for reading information of the RFID tag comprising the pseudo ID, the key is transmitted; and if a pseudo ID generated using the key is equal to the pseudo ID received in response to the information request signal, an RFID of the RFID tag to read the information of the RFID tag is received.

Abstract: A method of managing a user key for a broadcast encryption. The method includes assigning numbers to respective users and arranging the users on a ring-shaped structure in order to map hash chains onto the respective nodes of a ring-shaped structure. The method further includes making random node keys correspond to the respective nodes, one by one, constructing the hash chains from the corresponding node keys using a hash function, and successively mapping the constructed hash chains onto the nodes of the ring-shaped structure.

Abstract: A conference session key distribution method used in an ID-based cryptographic system includes selecting two different temporary secret keys, generating a message and generating session key generation variables using the temporary secret keys of a session initiating party. Only valid participating parties receive the session key generation variables. Each party determines the session shared key from the session key generation variables.

Abstract: A radio frequency identification (RFID) tag encryption method and system using a broadcast encryption (BE) scheme are provided by encrypting an ID of an RFID tag, storing the encrypted ID in a server and the RFID tag, and storing information relating to a reader authorized to read out the RFID tag in the server so that the reader can read out the RFID tag by decrypting the encrypted ID based on the encrypted ID information read from the RFID tag and the reader information. When readers read out ID data from the RFID tag, a privileged reader can read the data. Thus, it is possible to block unintended information leakage to the readers. In addition, user usability can be enhanced since an attacker cannot perform an access lock on the RFID tag.

Abstract: A digital signature method based on identification information of one or more group members who belong to a group includes: a) a group parameter generating operation generating group public key information and group secret key information corresponding to the group; b) a member registering operation generating member secret key information using identification information of the group members who belong to the group and an identification information digest value obtained by applying a predetermined hash function to the identification information, and transmitting the member secret key information to the group members; c) a digital signing operation generating a digital signature by applying a predetermined signature algorithm to the identification information and the identification information digest value, and transmitting the generated digital signature and a message; and d) an authentication operation verifying a validity of the digital signature by applying a predetermined authentication algorithm to the

Abstract: A radio frequency identification (RFID) tag encryption method and system using a broadcast encryption (BE) scheme are provided by encrypting an ID of an RFID tag, storing the encrypted ID in a server and the RFID tag, and storing information relating to a reader authorized to read out the RFID tag in the server so that the reader can read out the RFID tag by decrypting the encrypted ID based on the encrypted ID information read from the RFID tag and the reader information. When readers read out ID data from the RFID tag, a privileged reader can read the data. Thus, it is possible to block unintended information leakage to the readers. In addition, user usability can be enhanced since an attacker cannot perform an access lock on the RFID tag.