Abstract: A terminal writes first encrypted data in which a communication key and an owner ID are encrypted by using a public key into a second recording medium, and this medium is mounted to a communication apparatus so that the first encrypted data are transmitted to a server. The server sends second encrypted data which it acquires by encrypting a content decryption key by using the communication key which the server acquires by decrypting the received first encrypted data by using a secret key to the communication apparatus, and causes the communication apparatus to record them into the second recording medium. The terminal decrypts a content stored in a first recording medium by using the content decryption key which it acquires by decrypting the second encrypted data read from the second recording medium by using the communication key.

Abstract: A log output device and a program are provided, which append a signature to a log, prevent an undetectable tampering (alteration, insertion, deletion, etc.), and are able to narrow tampered position if tampered. The log output device forms a log record including a data part and a hash part, and outputs to a disk; the hash part is formed by combining a hash of the data part (data hash) and a hash of the hash part of the previous record (link hash); a signature is appended to only a part of records of a hash chain; when outputting the record to the disk, a copy of the hash part of the record is maintained on a process memory; when outputting next record, the hash part of the latest record on the disk and the hash part maintained on the process memory are compared; if they are matched, the record on the disk is determined as not being tampered, and if mismatched, the record is determined as tampered.

Abstract: A terminal writes first encrypted data in which a communication key and an owner ID are encrypted by using a public key into a second recording medium, and this medium is mounted to a communication apparatus so that the first encrypted data are transmitted to a server. The server sends second encrypted data which it acquires by encrypting a content decryption key by using the communication key which the server acquires by decrypting the received first encrypted data by using a secret key to the communication apparatus, and causes the communication apparatus to record them into the second recording medium. The terminal decrypts a content stored in a first recording medium by using the content decryption key which it acquires by decrypting the second encrypted data read from the second recording medium by using the communication key.

Abstract: A license delivery system 1000 allows intermediate nodes to modify a license within a range allowed by a license issuer. According to the license delivery system 1000, each of the intermediate nodes involved in the license delivery can verify if the license modifications have been correctly done by the intermediate nodes. Also according to the license delivery system 1000, a license issuer apparatus 2 adds, to an original license, original allowed modification information which defines a modifiable range of the original license. The intermediate nodes sequentially append, to a license 1 issued by the license issuer apparatus, the respective modified licenses that are modified within the modifiable range defined by the original allowed modification information.

Abstract: A digital content management system to decide whether or not a digital content is available depending on a location of a user who desires to use the digital content is provided. A digital content use right management system includes a digital content server device 1 to store an encrypted digital content, a license server device 2 to generate and transmit license data 4 containing an available location of the digital content and a decryption key to decrypt the digital content, and a client device 3 to receive the digital content from the digital content server device 1, to receive the license data 4 from the license server 2, and based on a condition for use defined by its use condition, to determine whether or not to decrypt the digital content with the decryption key contained in the license data 4.