The security of digital images attracts much attention recently, and many image encryption methods have been proposed. In ISCAS2000, a new chaotic key-based algorithm (CKBA) for image encryption was proposed. This paper points out CKBA is very weak to the chosen/known-plaintext attack with only one plainimage, and its security to brute-force ciphertext-only attack is overestimated by the authors. That is to say, CKBA is not secure at all from cryptographic viewpoint. Some experiments are made to show the feasibility of the chosen/known-plaintext attack. We also discuss some remedies to the original scheme and their performance, and we find none of them can essentially improve the security of CKBA.

The use of digital video offers immense opportunities for creators; however, the ability for anyone to make perfect copies and the ease by which those copies can be distributed also facilitate misuse, illegal copying and distribution (“piracy”), plagiarism, and misappropriation. Popular Internet software based on a peer-to-peer architecture has been used to share copyrighted movies, music, software, and other materials. Concerned about the consequences of illegal copying and distribution on a massive scale, content owners are interested in digital rights management (DRM) systems which can protect their rights and preserve the economic value of digital video. A DRM system protects and enforces the rights associated with the use of digital content. Unfortunately, the technical challenges for securing digital content are formidable and previous approaches have not succeeded. We overview the concepts and approaches for video DRM and describe methods for providing security, including the roles of encryption and video watermarking. Current efforts and issues are described in encryption, watermarking, and key management. Lastly, we identify challenges and directions for further investigation in video DRM.

Recently, a chaos-based image encryption scheme called RCES (also called RSES) was proposed. This paper analyzes the security of RCES, and points out that it is insecure against the known/chosen-plaintext attacks: the number of required known/chosen plain-images is only one or two. In addition, the security of RCES against the brute-force attack was overestimated. Both theoretical and experimental analyses are given to show the performance of the suggested known/chosenplaintext attacks. The insecurity of RCES is due to its special design, which makes it a typical example of insecure image encryption schemes. Some lessons are drawn from RCES to show some common principles for ensuring the high level of security of an image encryption scheme.

Abstract — Two approaches for integrating encryption with multimedia compression systems are studied in this research, i.e. selective encryption and modified entropy coders with multiple statistical models. First, we examine the limitations of selective encryption using cryptanalysis, and provide examples that use selective encryption successfully. Two rules to determine whether selective encryption is suitable for a compression system are concluded. Next, we propose another approach that turns entropy coders into encryption ciphers using multiple statistical models. Two specific encryption schemes are obtained by applying this approach to the Huffman coder and the QM coder. It is shown that security is achieved without sacrificing the compression performance and the computational speed. This modified entropy coding methodology can be applied to most modern compressed audio/video such as MPEG audio, MPEG video and JPEG/JPEG2000 images. Index Terms — multimedia encryption, confidentiality, G.723.1 speech coding, CELP, Huffman coding, selective encryption, QM

We propose selective bitplane encryption to provide secure image transmission in low power mobile environments. Two types of ciphertext only attacks against this scheme are discussed and we use the corresponding results to derive conditions for a secure use of this technique.

The security of multimedia data in digital distribution networks is commonly provided by encryption, i.e., the mathematical process that transforms a plaintext message into unintelligible ciphertext. Nevertheless, the classical and modern ciphers have all been developed for the simplest form of multimedia data, i.e., text, and are not appropriate for higher forms such as images and video with very large file sizes. Selective encryption is a recent approach to reduce the computational requirements for huge volumes of multimedia data in distribution networks with different client device capabilities. In this paper, we provide a survey and classification of the proposed schemes, discuss the current issues and present some future directions.

Secrete permutations are widely used in multimedia encryption algorithms, and many permutation-only ciphers have been proposed in recent years for protection of different types of multimedia data, especially digital images and videos. Based on a normalized encryption/decryption model, this paper analyzes the security of permutation-only image ciphers working in spatial domain from a general perspective, taking a recentlyproposed permutation-only image cipher called HCIE (hierarchical chaotic image encryption) as a typical example. It is pointed out that all permutation-only image ciphers are insecure against known/chosen-plaintext attacks in the sense that only O (log L (MN)) known/chosen plain-images are enough to break the ciphers, where MN is the size of the image and L is the number of different pixel values. Also, it is found that the attack complexity is only O(n ), where n is the number of known/chosen plain-images used. Following the results, it is found that hierarchical permutation-only image ciphers such as HCIE are less secure than normal (i.e., non-hierarchical) permutationonly image ciphers. Experiments are shown to verify the feasibility of the known/chosen-plaintext attacks. The cryptanalysis result is then generalized to permutation-only image ciphers working in frequency domain and video ciphers. In conclusion, secret permutations have to be combined with other encryption techniques to design highly secure multimedia encryption sysThis research was partially supported by the AIIS Inc., NY, USA, the Applied R&D Centers of the City University of Hong Kong (under grants no. 9410011 and no. 9620004), and the National Natural Science Foundation of China (under grant no. 60202002).

The security of digital images attracts much attention recently, and many different image encryption methods have been proposed. In 1999, J.-C. Yen and J.-I. Guo proposed a novel image encryption algorithm called BRIE (Bit Recirculation Image Encryption) . This paper points out that BRIE is not secure enough from strict cryptographic viewpoint. It has been found that some defects exist in BRIE, and a known/chosen-plaintext attack can break BRIE with only one known/chosen plain-image. Experiments are made to verify the defects of BRIE and the feasibility of the attack.

The recent advances in technology, especially in computer industry and communications, allowed potentially enormous market for distributing digital multimedia content through the Internet. However, the proliferation of digital documents, multimedia processing tools, and the worldwide availability of Internet access has created an ideal medium for copyright fraud and uncontrollable

Abstract: The newly adopted MPEG-4 Fine Granularity Scalability (FGS) video coding standard offers easy and flexible adaptation to varying network bandwidths and different application needs. Encryption for FGS should preserve such adaptation capabilities and enable intermediate stages to process encrypted data directly without decryption. In this paper, we propose two novel encryption algorithms for MPEG-4 FGS that meet these requirements. The first algorithm encrypts an FGS stream (containing both the base and the enhancement layers) into a single access layer and preserves the original fine granularity scalability and error resilience performance in an encrypted stream. The second algorithm encrypts an FGS stream into multiple quality layers divided according to either PSNR or bitrates, with lower quality layers being accessible and reusable by a higher quality layer of the same type, but not vice versa. Both PSNR and bitrate layers are supported simultaneously so a layer of either type can be selected on the fly without decryption. The base layer for the second algorithm may be unencrypted to allow free view of the content at low quality or content-based search of a video database without decryption. Both algorithms are fast, error-resilient, and have negligible compression