Research Overview
Digital contents, e.g. still images, motion pictures, musics, and text documents, have diverse applications areas, because they can be easily copied, edited, and transmitted. On the other hand, they have a potential problem that they may be illegally distributed and/or used, which leads to a great loss for not only each individual user and/or enterprise, but also content industry itself. In this project, we do research on digital content protection, to protect such illegal distribution and/or usage, and eventually to promote secure content creation and distribution. In detail, our research items consist of three issues: "Secure Home networking", secure contents sharing and backup within home networking while protecting the rights of the content owners, and "Next Generation Optical Media Content Protection", protection of the illegal copying and tracing of the illegally distributed contents for next generation optical media such as Blu-Ray."Off-line Content Protection", off-line file protection within enterprises.
Off-line Content Protection
When a user accesses data stored in the server, he/she is usually certified by user ID, password, or a public key cryptosystem, and data is usually transmitted after encrypted. However, once the data is downloaded to a local storage or a portable media, they are stored after decrypted, and possibly accessed by someone else. The confidential information leakage accident by the P2P application proves the fact. To prevent such accidents, we are developing an off-line content protection system by off-line certification, which protects all the files stored in portable PC or portable media from unlawful access, by storing files being encrypted, allowing decryption only for authorized users. To achieve this, we apply "broadcast encryption" technology, which has a good track record in a copy protection system of DVD or an SD memory card, and is further adopted as a copy protection system of next-generation optical media.
Secure Home Networking
Pervasion of broadband, start of terrestrial broadcasting, and such have promoted the "home networking", in which each family has plural of digital devices which are connected each other. At the same time, everal content protection technologies are standardized, and one of the examples is the "copy one generation" restriction for Japanese terrestrial programs, effective since April, 2004. However, these restrictions cause a problem that contents cannot be shared even within family. In this project, we do research on a technology which allows contents sharing and backup within each home networking while prohibiting illegal copying and distribution outside the home networking.
The chart below shows the overview of the secure home networking. Contents can be shared and you can make as many backup copies as you like within a home networking without having the restriction of the distance. On the other hand, contents outside the home networking are bound to existing content protection technologies, such as CPRM and DTCP.
Secure Home Networking
Next Generation Optical Media Content Protection
Pervasion of High-Def contents are accelerated by the start of terrestrial broadcasting and shipment of Blu-Ray device and media. Accordingly, protection of these contents is becoming a very important issue. In this project, we do research on the technology of illegal copy protection and traceability of illegally distributed contents of these contents, and proposing it to AACS-LA (Advanced Access Content System Licensing Administrator), the organization to develop and standardize the content protection technologies on the next generation optical media.
The chart below shows the traceability technology for optical media, which we call "Sequence Key". This technology can specify the users and/or devices from which contents are illegally distributed and/or copied. This technology is adopted by "AACS Pre-recorded Video Book Revision 0.90", issued by AACS-LA on April, 2005.
"Sequence Key", tracing technology in next generation optical media content protection
Papers
- K.Kamijo, M.Sakamoto, Y.Niimura, and S.Furuichi, "An off-line content protection System," DICOMO, IPSJ, 2007 (in Japanese).
- N.Morimoto and K.Kamijo, "Basics of security on audio/visual media," Journal of ITE, Vol. 59, No. 9, pp.377-382, 2005 (in Japanese).
- A.Sato and K.Kamijo, "An Off-line Media Distribution System that Revokes the Pirated Media," DICOMO2004, IPSJ, 2004 (in Japanese).
- K.Kamijo, "Broadcast Encryption with Key Re-arrangement Function," DICOMO2004, IPSJ, 2004 (in Japanese).