The objective of this chapter introduces an advanced encryption of MP3 and MPEG-4 coder with a quality degradation-based security model. For the MP3 audio, the magnitude, and phase information of modified discrete cosine transform (MDCT) coefficients is encrypted. DCT coefficients and motion vectors (MVs) are used for the scrambling of the MPEG-4 video. This encryption scheme has a level of security, secures in perception, keeps format compliance, and obtains high time efficiency though reducing the encrypted the volumes of multimedia contents. These properties make it practical to incorporate encryption and decryption process into compression and decompression process, and thus suitable for secure A/V transmission or sharing.
With the advance of multimedia technology, multimedia sharing among multiple devices has become the main issue. This allows users to expect the peer-to-peer distribution of unprotected and protected contents over public network. Many audio and video (A/V) processing software including DVD players, CD rippers, MP3 encoders, and A/V players have been posted for free on the Web allowing users to build their own A/V record collections from their own CD and DVD. Inevitably, this situation has caused an incredible piracy activity and some Web sites have begun to provide copyrighted A/V data for free. In order to protect the contents from illegal attacks, digital rights management (DRM) is required as shown in Figure 1.
Application of DRM technique
The DRM system generally provides two essential functions: management of digital rights by identifying, describing, and setting the rules of the content usage, and digital management of right by securing the contents and enforcing usage rules. The basic principle of the DRM model (Schneier, 1996; Piva, 2002; Petitcloas, 1999) is to separate and identify three core entities: Users, Content, and Rights. Users can be any type of users from a rights holder to an end-consumer. Content is any type of contents at any level of aggregation. A right is an expression of permissions, constraints, and obligations between Users and Content. This model provides the greatest flexibility when assigning rights to any combination or layering of Users and Content. Figure 2 shows the example of contents distribution service using DRM. In Figure 2, a user A requests image, audio, or video in the network and goes through payment. Billing system informs payment approval, and then CP delivers encrypted contents to only an authorized user through the network.
Example of the contents distribution service using DRM
Various encryption techniques for DRM have been researched. These techniques are classified into two approaches: scrambling and watermarking. Scrambling that is generally based on old and proven cryptographic tools, efficiently ensures confidentiality, authenticity, and integrity of messages. However, it does not protect against unauthorized copying after the message has been successfully transmitted and descrambled (Matsunaga, et al., 1989; Schneier, 1996; Spanos, et al., 1995). This kind of protection can be handled by watermarking (Piva, 2002; Aeng, 2003), which is a more recent topic that has attracted a large amount of research and is perceived as a complementary aid in encryption. A digital watermark is a piece of information inserted and hidden in the media content (Bassia, 2001; Borujeni, 2000; Cox, 2000; Li, et al., 2004; Neubauer, et al., 1998; Yeh & Kuo, 1999). This information is imperceptible to a human observer but can be easily detected by a computer. Moreover, the main advantage of this technique is to provide the nonseparability of the hidden information and the content.
Key Terms in this Chapter
Joint Encryption: This technology is the joint of each encryption which is independently the difference process for encryption. It has ability that is a level of security against accessing the unauthorized device or users.
A/V Scrambling: This technology and contents scrambling system are the same. The purpose of contents scrambling system is twofold. First and foremost, it prevents byte-for-byte copies of an MPEG stream from being playable since such copies will not include the keys that are hidden on the lead-in area of the protected DVD disk. Second, it provides a reason for manufacturers to make compliant devices, since contents scrambling system scrambled disks will not play on noncompliant devices. Anyone wishing to build compliant devices must obtain a license, which contains the requirement that the rest of the copy-protection system be implemented
A/V Encryption: This algorithm can be used as one of access content system. The access content system (ACS) is a standard for content distribution and digital rights management, intended to restrict access to and copying of the next generation of optical discs and DVDs. The specification was publicly released in Apr. 2005 and the standard has been adopted as the access restriction scheme for HD DVD and Blu-ray Disc (BD).
Copyright Protection: The mechanisms that prevent data, usually digital data, from being copied. The term “copyright protection” is occasionally seen in this usage, but is an error; copy protection is the usual term. Permission is not granted to use these images, which are protected by copyright.
Partial Encryption: It is similar to the joint encryption. However, this technology is how to degree the robustness of the encryption. And it provides some information of unauthorized consumer in advertizing the contents.
Authorized Device: The technology may be a physical device that an authorized user of computer services is given to aid in authentication. An authorization is the concept of allowing access to resources only to those permitted to use them. More formally, authorization is a process (often part of the operating system) that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. Resources include individual files’ or items’ data, computer programs, computer devices and functionality provided by computer applications.
Watermarking and Scrambling: A watermarking system consists of an embedding algorithm and a detecting function. And scrambling is generally based on old and proven cryptographic tools, efficiently ensures confidentiality, authenticity, and integrity of messages. This mechanism is the combination ones.
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