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Content Protection Solutions for Digital Home Networks

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Definition: Content protection solutions include techniques and standards used to protect multimedia content in home networks and devices.

Each of the solutions for digital home networks defines a means of associating the Copy Control Information (CCI) with the digital content it protects. The CCI communicates the conditions under which a consumer is authorized to make a copy. An important subset of CCI is the two Copy Generation Management System (CGMS) bits for digital copy control: “11” (copy-never), “10” (copy-once), “01” (no-more-copies), and “00” (copy-free). The integrity of the CCI should be ensured to prevent unauthorized modification. The CCI can be associated with the content in two ways: (1) the CCI is included in a designated field in the A/V stream, and (2) the CCI is embedded as a watermark into the A/V stream.

The Content Scramble System (CSS) was the first of its kind for protecting multimedia content on DVD players. CSS has a hierarchy of keys: master key, disk key, and title key. DVD Copy Control Association (CCA) has assigned each manufacturer a distinct master key that is embedded in all DVD players. The unique disk key belonging to each disk is encrypted by all the master keys, and this information is stored on every disk. The player decrypts the disk key with its own master key. The disk key decrypts the title key, and the title key decrypts the movie on the DVD. If a particular master is key compromised, it is replaced by a key used in the subsequent manufacturing of DVD players. With the new key assignment, future releases of DVDs cannot be played on the cloned players manufactured with the compromised key. A software implementation of CSS for a DVD drive was hacked in 1999. The software called DeCSS can be used to break the CSS encryption, allowing the decryption of protected DVDs. CSS-protected video is decrypted during playback on the compliant DVD player or drive.

Content Protection for Pre-Recorded Media (CPPM) Specification is designed for protecting audio on DVD-ROM. CPPM-protected audio is decrypted during playback on the compliant DVD player or drive. Content Protection for Recordable Media (CPRM) Specification is designed for protecting audio-visual (A/V) content on recordable DVDs. The A/V stream coming from a source device is re-encrypted before recording on a DVD recordable disc. During playback, the compliant player derives the decryption key.

The 4C/Verance watermark technology embeds inaudible digital data into audio content. The compliant playback or recording device detects the CCI represented by the watermark, and responds accordingly.

The content providers are interested in watermarking DVD content as a second line of defense. In this scheme, invisible watermarks are embedded into video content. The compliant playback or recording device detects the CCI represented by the watermark and responds accordingly. If a copy is authorized, the compliant recorder creates and embeds a new watermark to represent “no-more-copies.”

The Digital Transmission Content Protection (DTCP) Specification defines a cryptographic protocol for protecting audio/video entertainment content from unauthorized copying, intercepting, and tampering as it traverses digital transmission mechanisms such as a high-performance serial bus that conforms to the IEEE 1394-1995 standard. The source and sink devices authenticate each other, and establish shared secrets. The A/V content is encrypted across the interface using a content key derived from several parameters. The encryption key is renewed periodically.

High-bandwidth Digital Content Protection (HDCP) is a specification developed by Intel Corporation to protect digital entertainment content across the Digital Visual Interface (DVI) and High Definition Multimedia Interface (HDMI). DVI and HDMI are two of the interfaces protected by HDCP. Video transmitter authenticates the receiver, and establishes shared secrets with it. A/V content is encrypted across the interface with a key based on shared secrets. The encryption key is renewed frequently.

Content Repurposing for Small Devices - INTRODUCTION, BACKGROUND, METHODS OF CONTENT REPURPOSING, Repurposing Strategies, Redrawing the Display, FUTURE WORK, CONCLUSION [next] [back] Content Management in Multimedia News Systems

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