User terminal for receiving license

A license distribution server encrypting a license necessary for using an encrypted content and distributing the encrypted license to a user terminal connected in an information transmittable manner, the server comprising:

• a license storing unit which stores the license;
• a license encrypting unit which produces an encryption key by the same method as that by the user terminal using the same seed as the seed used by the user terminal to produce an encryption key for decrypting the encrypted license and encrypting the license for distribution;
• and
• a license distribution unit which distributes the encrypted license for distribution to the user terminal.

A secure method of receiving a license at a user terminal in a digital content distribution system comprising a content distribution server that distributes a content, a license distribution server that distributes a license, and the user terminal connected to these servers, the method, carried out by the user terminal:

• transmitting a content obtaining request including a content ID that uniquely specifies a content to the content distribution server;
• receiving the content from the content distribution server;
• producing a seed for producing a license encryption key for distribution to be used for encrypting a license and storing the seed in a tamper resistant module;
• transmitting a license obtaining request including the seed to the license distribution server;
• receiving an encrypted license for distribution from the license distribution server;
• producing the encryption key used by the license distribution server to encrypt the license using the seed stored in the tamper resistant module by the same method as that by the license distribution server, decrypting the license, and checking a hash value;
• deleting the seed stored in the tamper resistant module;
• decrypting the content using the decrypted license;
• producing a new arbitrary title key for storing in the user terminal and re-encrypting the content;
• and
• replacing the title key of the license with the title key for storing and encrypting the license in a format resistant to unauthorized access.

A secure method of receiving a license at a user terminal in a digital content distribution system comprising a content distribution server that distributes a content, a license distribution server that distributes a license, and the user terminal connected to these servers, the method, carried out by the user terminal:

• transmitting a content obtaining request including a content ID that uniquely specifies a content to the content distribution server;
• receiving a content from the content distribution server;
• producing a seed for producing a license encryption key for distribution to be used for encrypting a license in a tamper resistant module, storing a seed identifier association table in which a seed and a seed identifier to identify the seed are associated with each other, and storing the seed identifier outside the tamper resistant module;
• transmitting a license obtaining request including the seed to the license distribution server;
• receiving an encrypted license for distribution from the license distribution server;
• obtaining a seed corresponding to the seed identifier stored outside the tamper resistant module based on the seed identifier association table stored in the tamper resistant module, producing the encryption key used by the license distribution server to encrypt the license by the same method as that by the license distribution server, decrypting the license, and checking a hash value;
• deleting the seed and the corresponding seed identifier stored in the tamper resistant module from the seed identifier association table;
• decrypting the content using the decrypted license;
• producing a new arbitrary title key for storing in the user terminal and re-encrypting the content;
• and
• replacing the title key of the license with the title key for storing and encrypting the license in a format resistant to unauthorized access.

A secure method of receiving a license at a user terminal in a digital content distribution system comprising a content distribution server that distributes a content, a license distribution server that distributes a license, and the user terminal connected to these servers, the method, carried out by the user terminal:

• transmitting a content obtaining request including a content ID that uniquely specifies a content to the content distribution server;
• receiving a content from the content distribution server;
• producing and storing a seed for producing a license encryption key for distribution to be used for encrypting a license in a tamper resistant module, encrypting the seed in a format resistant to unauthorized access, and storing the encrypted seed outside the tamper resistant module;
• transmitting a license obtaining request including the seed to the license distribution server;
• receiving the encrypted license for distribution from the license distribution server;
• producing the encryption key used by the license distribution server to encrypt the license by the same method as that by the license distribution server based on the seed stored in the tamper resistant module when there is the seed present in the module and the seed encrypted in the format resistant to unauthorized access and stored outside the tamper resistant module when the seed is not present in the module, decrypting the license, and checking a hash value;
• deleting the seed stored in the tamper resistant module when the stored seed is present in the tamper resistant module in the previous step;
• decrypting the content using the decrypted license;
• producing a new arbitrary title key for storing in the user terminal and re-encrypting the content;
• replacing the title key of the license with the title key for storing, and encrypting the license in a format resistant to unauthorized access;
• and
• deleting the seed encrypted in the format resistant to unauthorized access and stored outside the tamper resistant module.

A secure method of receiving a license at a user terminal in a digital content distribution system comprising a content distribution server that distributes a content, a license distribution server that distributes a license, and the user terminal connected to these servers, the method, carried out by the user terminal:

• transmitting a content obtaining request including a content ID that uniquely specifies a content to the content distribution server;
• receiving a content from the content distribution server;
• producing a seed for producing a license encryption key for distribution to be used for encrypting a license in a tamper resistant module, storing a seed identifier association table in which a seed and a seed identifier are associated with each other, and encrypting a seed and a seed identifier to be used by the license distribution server to encrypt a license for storing outside the tamper resistant module;
• transmitting a license obtaining request including the seed to the license distribution server;
• receiving an encrypted license for distribution from the license distribution server;
• producing the encryption key used by the license distribution server to encrypt the license by the same method as that by the license distribution server based on the seed corresponding to the seed identifier stored outside the tamper resistant module when the seed is present in the module and the seed encrypted in the format resistant to unauthorized access and stored outside the tamper resistant module when the seed is not present in the module, decrypting the license, and checking a hash value;
• deleting the seed and the corresponding seed identifier stored in the tamper resistant module only when the seed corresponding to the seed identifier is present in the tamper resistant module in the previous step;
• decrypting the content using the decrypted license;
• producing a new arbitrary title key for storing in the user terminal and re-encrypting the content;
• replacing the title key of the license with the title key for storing and encrypting the license in a format resistant to unauthorized access;
• and
• deleting the seed and the seed identifier encrypted in the format resistant to unauthorized access and stored outside the tamper resistant module.

A license receiving program for obtaining a necessary license for using a content from a license distribution server connected in an information transmittable manner, the program enabling a computer to serve as:

• a seed producing/storing unit which produces and stores a seed for producing an encryption key to be used by the license distribution server to encrypt a license;
• a license receiving unit which receives the license encrypted using the encryption key produced by the license distribution server based on the seed;
• and
• an encryption conversion unit which produces an encryption key by the same method as that by the license distribution server based on the seed and decrypting the encrypted license using the encryption key.

A secure device accessible by a user terminal that obtains a license necessary for using a content from a license distribution server connected in an information transmittable manner, the device comprising:

• a tamper resistant module externally accessible through a specially permitted path having a seed producing/storing unit which produces and stores a seed for producing an encryption key to be used by the license distribution server to encrypt a license and an encryption conversion unit which produces an encryption key by the same method as that by the license distribution server based on the seed, and decrypting the license encrypted using the encryption key;
• and
• an information storing portion having a secure storing region accessible through the tamper resistant module and a general storing region externally accessible without special permission,
• the seed producing/storing unit producing and storing a seed for producing an encryption key for an encrypted license obtained by the user terminal from the license distribution server,
• the encryption conversion unit producing an encryption key based on the produced seed and decrypting the license using the produced encryption key,
• the seed producing/storing unit deleting the seed when the decryption of the license is complete,
• the encryption conversion unit decrypting the content obtained by the user terminal using the decrypted license and then re-encrypting the license and content using a title key unique to a receiving terminal or a secure device.

A user terminal obtaining encrypted data from a server connected in an information transmittable manner, comprising:

• a seed producing/storing unit which produces and stores a seed for producing an encryption key to be used by the server to encrypt data;
• a data receiving unit which receives the data encrypted using the encryption key produced by the server based on the seed;
• and
• an encryption conversion unit which produces an encryption key based on the seed by the same method as that by the server and decrypting the encrypted data using the encryption key,
• wherein the seed is deleted from the seed producing/storing unit when the decryption of the data is complete.