An electronic device includes a first non-volatile memory and an application circuit. The first non-volatile memory stores first encrypted data encrypted with a global key. The application circuit includes a second non-volatile memory, a decryption unit, a local key unit, and an encryption unit. The second non-volatile memory stores the global key. The decryption unit is coupled to the first non-volatile memory and the second non-volatile memory. The decryption unit retrieves the global key from the second non-volatile memory and decrypts the first encrypted data with the global key to generate plain data. The local key unit generates or stores a local key. The encryption unit is coupled to the local key unit. The encryption unit encrypts the plain data with the local key to generate second encrypted data and overwrites the first encrypted data in the first non-volatile memory with the second encrypted data.

A configuration in which a reliable source of illegal copy content is analyzed using content in which a reproduction path can be set is realized. Content which has a segment area including a plurality of items of variation data which can be decrypted using different keys and in which a reproduction path corresponding to the selected variation data can be set is used. Each item of variation data is configured such that embedded information such as a digital watermark can be acquired from decrypted data. Each item of variation data includes a 192-byte source packet or a 6144-byte aligned unit. A reproduction device selects and reproduces one item of variation data from each segment area on the basis of a variation data identifier recorded in the variation data.

A non-transitory tangible recording medium stores recorded AV data. The AV data includes a system stream file played by a playback device and a management information file having management information corresponding to the system stream file. The system stream file includes a first segment including repeated a first data unit that be decrypted using a first decryption key that the playback device individually has and a second data unit that cannot be decrypted by the first decryption key. The system stream file also includes a second segment which can be decrypted using a second decryption key that the playback device has in common with another playback device. The management information file has a start source packet number, which identifies a start source packet out of a plurality of source packets storing an I-picture that is a random access point, and the start source packet is situated in the second segment.

A configuration capable of performing reliable source analysis of illegal copy content using content in which a reproduction path is settable is implemented. Content in which an individual segment region including a plurality of pieces of variation data which include different identification information embedded therein and are decryptable using different keys and a common segment region including single data are provided, and variation data is configured with an aligned unit is set. A content reproducing device calculates a reproduction path by applying a device key and selects and reproduces an aligned unit corresponding to the reproduction path on the basis of a variation data identifier recorded in an adaptation field in a plain text region at the head of a plurality of aligned units constituting the variation data.

An electronic device includes a first non-volatile memory and an application circuit. The first non-volatile memory stores first encrypted data encrypted with a global key. The application circuit includes a second non-volatile memory, a decryption unit, a local key unit, and an encryption unit. The second non-volatile memory stores the global key. The decryption unit is coupled to the first non-volatile memory and the second non-volatile memory. The decryption unit retrieves the global key from the second non-volatile memory and decrypts the first encrypted data with the global key to generate plain data. The local key unit generates or stores a local key. The encryption unit is coupled to the local key unit. The encryption unit encrypts the plain data with the local key to generate second encrypted data and overwrites the first encrypted data in the first non-volatile memory with the second encrypted data.

A non-transitory tangible recording medium stores recorded AV data. The AV data includes a system stream file played by a playback device and a management information file having management information corresponding to the system stream file. The system stream file includes a first segment including repeated a first data unit that be decrypted using a first decryption key that the playback device individually has and a second data unit that cannot be decrypted by the first decryption key. The system stream file also includes a second segment which can be decrypted using a second decryption key that the playback device has in common with another playback device. The management information file has a start source packet number, which identifies a start source packet out of a plurality of source packets storing an I-picture that is a random access point, and the start source packet is situated in the second segment.

A playback method and a playback device for playing a system stream file are provided. The playback method uses the playback device having one or more memories and circuitry to play the system stream file. The playback method includes reading the system stream file and identifying whether the system stream file to be played back is a first system stream file having a first file format or a second system stream file having a second file format. If the system stream file to be played back is the first system stream file, the method further includes converting a file format of the system stream file that has been read out from the first file format into the second file format. The playback method further includes decoding the system stream file having the second file format.

Content individualization, including: encrypting a first part of a source data set using a first key creating a first encrypted data set; encrypting a second part of the source data set using a second key creating a second encrypted data set; encrypting the second part of the source data set using a third key creating a third encrypted data set; and combining the first encrypted data set, the second encrypted data set, and the third encrypted data set to form a final encrypted data set. Key words include watermarking and content individualization.

A non-transitory tangible recording medium storing AV data having a system stream file is provided. The system stream file is played by a playback device. The system stream file includes an individual decryption key and a common decryption key. The individual decryption key is owned individually by each of multiple playback devices. The common decryption key is owned in common by the playback devices. The system stream file includes a first system stream file to be played back using both the individual decryption key and the common decryption key. The system stream file also includes a second system stream file to be played back using only the common decryption key among the individual decryption key and the common decryption key.

A non-transitory tangible recording medium storing AV data having a system stream file is provided. The system stream file is played by a playback device. The system stream file includes an individual decryption key and a common decryption key. The individual decryption key is owned individually by each of multiple playback devices. The common decryption key is owned in common by the playback devices. The system stream file includes a first system stream file to be played back using both the individual decryption key and the common decryption key. The system stream file also includes a second system stream file to be played back using only the common decryption key among the individual decryption key and the common decryption key.