Abstract: A content data reproducing method includes: decrypting encrypted data to generate plain-text data; dividing the plain-text data into decrypted content data and reproduction management information; sending the reproduction management information to a user space; storing the decrypted content data in a secret buffer; obtaining the decrypted content data as reproduction target data from the secret buffer and transmitting the reproduction target data to a decoder; and decoding the reproduction target data by the decoder.

Abstract: A content data reproducing method includes: decrypting encrypted data to generate plain-text data; dividing the plain-text data into decrypted content data and reproduction management information; sending the reproduction management information to a user space; storing the decrypted content data in a secret buffer; obtaining the decrypted content data as reproduction target data from the secret buffer and transmitting the reproduction target data to a decoder; and decoding the reproduction target data by the decoder.

Abstract: A validity information processing section determines a valid MKB and a valid intermediate key by referring to validity information in a recording medium, and, when an MKB and an intermediate key that are not valid have been rewritten, rewrites the validity information in the recording medium. An MKB processing section reads the valid MKB from the recording medium and performs updating processing on an MKB stored in the key management device, and rewrites the non-valid MKB in the recording medium. An intermediate key processing section reads the valid intermediate key from the recording medium and decrypts and re-encrypts the read intermediate key with an authentication key, and rewrites the non-valid intermediate key into the re-encrypted intermediate key.

Abstract: A server carries out a network position check process for a client which requests to use a content, and the server generates a vicinity check information including a requirement for authorizing omission of the network position check process for the client when the client thereafter requests to use the content again after the network position check process determines that the client is located in a local area network where the server belongs. At least one of the server and the client retains the vicinity check information to determine based on the vicinity check information whether the network position check process can be omitted when the client thereafter requests to use the content again.

Abstract: A storage medium control apparatus capable of improving the processing performance, while protecting copyright protection information in a security mode, includes: a secure resource which executes mutual authentication processing with an authentication area of a storage medium, and performs encryption or decryption of data; a normal resource which sends or receives data to or from the storage medium; an encryption control unit which performs encryption or decryption of data by controlling the secure resource in the secure mode; a storage medium control unit which sends or receives data encrypted by the encryption control unit or data decrypted by the encryption control unit to or from the storage medium by controlling the normal resource, in the secure mode; and a storage medium processing unit which performs predetermined processing for the data decrypted by the encryption control unit or unencrypted data read from the storage medium by the storage medium control unit.