Abstract: A method of managing a home network key in a home network environment, which has a key management server for managing the home network key and a plurality of home network devices, includes: allowing a home network device to generate device unique information and to transmit the device unique information to the key management server; allowing the key management server to generate a parameter for generating the home network key by using the device unique information and to transmit the parameter to the home network device; and allowing the home network device to generate the home network key by using the parameter. The generated home network key being independent of the device unique information.

Abstract: A method of revoking a public key of a content provider is provided. In a system in which a certificate authority certifies the public key of the content provider and the content provider transmits predetermined content to a user device using the certified public key, the method includes the user device determining whether the predetermined content is revoked by comparing a time when a signature of the public key is generated with a time when the public key is revoked. Accordingly, it is possible to allow the user device to identify content that must not be revoked according to the time when the public key is revoked and a revocation list which includes an exception list, thereby preventing rightly obtained content from being revoked.

Abstract: A method and apparatus are provided for protecting software by randomly distributing software code. The software protecting method includes: dividing software code into a plurality of protecting code fields and a plurality of general code fields; selecting at least one field to be shuffled among the protecting code fields and selecting at least one seed field among the general code fields; and shuffling codes of the selected field to be shuffled according to a shuffling rule generated using a random number generator on the basis of a code value of the selected seed field.

Abstract: A multimedia device having a function of backing up received broadcasting contents in a home network environment and a method of backing up the broadcasting contents. The multimedia device includes a local storage unit for storing received broadcasting contents, and a storage controlling unit for controlling storage of the broadcasting contents. When a space of the local storage unit is insufficient or when a user requests a backup, the storage controlling unit controls the device to transfer some of the stored broadcasting contents to a backup device. Accordingly, the multimedia device backs up the received broadcasting contents in various backup devices, thereby efficiently controlling the storage space of the local storage unit. Also, the multimedia device can prevent the backed-up contents from being arbitrarily reproduced or copied by another unauthorized multimedia device.

Abstract: A method and apparatus are provided for simply and securely limiting a number of times that contents can be accessed using a hash chain. The apparatus limiting a number of times contents are accessed by a user terminal includes a hash chain generator receiving information indicating selected contents by the user terminal and information indicating how many times (n) the user terminal has authority to access the selected contents and generating a hash chain including n hash values derived from a seed value, and a contents access manager deleting the hash values one by one from the hash chain whenever the user terminal accesses the selected contents such that the number of times the contents can be accessed by the user terminal is decreased by the number of deleted hash values.

Abstract: A scrambling apparatus and method are provided for increasing randomness without damaging compression efficiency of total video data by selectively and randomly performing conversion when converting motion vector codes of compressed video data into other motion vector codes indicating other motion vector values, and more particularly, by performing conditional conversion only if a predetermined condition is satisfied when selective conversion of motion vector codes is performed. The scrambling apparatus includes a conversion motion vector code table generator generating a conversion motion vector code table comprising motion vector codes obtained by converting motion vector codes corresponding to motion vector values of input video data in a standard motion vector code table; and a conversion controller randomly determining whether a certain motion vector value is encoded using the conversion motion vector code table or the standard motion vector code table.

Abstract: A home network system allowing a user to directly control joining or removing of member devices in a domain using a user interface and to effectively control a status change of the member devices of the domain and a management method therefor. The home network system includes: a master device, which forms a domain with more than one controlled device, transmits a predetermined domain key to the controlled devices included in the domain, generates a new domain key whenever a configuration of the domain is changed, and transmits the new domain key to the controlled devices remaining in the domain; and a control point, which provides a user interface allowing a user to directly change the configuration of the domain.

Abstract: A home domain building method and system that allow devices to join a home domain using smart cards. In the method, a master device reads device information from a smart card having a device ID and a device key as the device information of a guest device authenticated as a legal device and transmits a challenge request signal to the guest device, the guest device randomly generates a challenge value in response to the challenge request signal, the master device encrypts the challenge value using the device key of the guest device and transmits the encrypted challenge value to the guest device, the guest device decrypts the encrypted challenge value, and if the decrypted challenge value is the same as the challenge value generated in response to the challenge request signal, the guest device allows the master device to join the guest device in the home domain.

Abstract: Disclosed is a domain authentication method for exchanging content between devices. The domain authentication method for exchanging content between devices according to the present invention includes a first step of setting domain identification information into a predetermined device connected on a wired/wireless network; a second step of generating a domain secret key using the set domain identification information and predetermined device identification information; a third step of generating a predetermined first code value and transmitting a first packet encrypted with the first code value using the domain secret key generated in the second step; a fourth step of receiving a second packet that is encrypted with the first code value and a second code value; and a fifth step of decrypting the second packet received in the fourth step.

Abstract: A method of establishing a home domain capable of reproducing multimedia content, and a smart card therefor. The method includes creating a domain certificate for a reproducing device by inserting the smart card into the reproducing device, creating a session key by inserting the smart card into a home server, and verifying the domain certificate of the reproducing device and transmitting the created session key to the reproducing device if the device is a legitimate device. Alternatively, the method includes using an external certificate authority to determine whether the reproducing device is a legitimate device.

Abstract: An AV stream processing system includes an AV stream input unit which receives an AV stream having an AV content information field including first copy control information, and an AV content field including second copy control information, a determination unit which extracts the first and second copy control information from the received AV stream and determines whether the first copy control information has been modified, and an AV stream decryption unit which processes the received AV stream according to predetermined criteria, when the first copy control information has been modified.

Abstract: An AV stream processing system includes an AV stream input unit which receives an AV stream having an AV content information field including first copy control information, and an AV content field including second copy control information, a determination unit which extracts the first and second copy control information from the received AV stream and determines whether the first copy control information has been modified, and an AV stream decryption unit which processes the received AV stream according to predetermined criteria, when the first copy control information has been modified.

Abstract: A system for authenticating a content user, comprising a group common key that authenticates a user, a private key owned by the user, a trusted organization adapted to create and distribute the group common key, and to store personal information on the authenticated user and a temporary registration certificate issued to the authenticated user. A user apparatus converts the temporary registration certificate by means of a predetermined conversion method using the private key, and further provides the converted temporary registration certificate to a content provider prior to executing content provided by the content provider the content provider adapted to check whether the user has been authenticated by the trusted organization, using the group common key prior to providing the content.