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In recent years, image encryption has been broadly researched. Since a large proportion of images on Internet are compressed, and JPEG is the most widely adopted standards for image compression, a variety of joint image compression and encryption algorithms have been proposed. JPEG image encryption uses signal processing techniques as well as cryptographic techniques in different stages of the JPEG compression process. Based on the location where the encryption is taken place, these algorithms can be generally classified into three major categories: pre-compression encryption algorithms, in-compression encryption algorithms, and post-compression encryption algorithms, which correspond to conduct encryption operations before, during, and after the compression process. From this perspective of classification, the authors give a comprehensive survey on representative image encryption algorithms of each type, and show their properties and limitations. Some of the most recent encryption schemes that achieve protection at various positions of the compression process are selected for comparison, which are two pre-compression encryption algorithms, four in-compression encryption algorithms, and two post-compression encryption algorithms. Possible future research directions on designing joint JPEG compression and encryption schemes are provided in the end, which may facilitate solving application scenario-oriented JPEG security problems with new technologies.

Joint image encryption and compression schemes have shown their great potential values in protecting compressed images. To achieve the protection, a trade-off between encryption power and compression ability needs to be considered. In this paper, we propose two new joint encryption and compression schemes, where one scheme emphasizes compression performance, another highlights protection performance. For a given plain-image, we first raster scan it into non-overlapping 16 × 16 blocks, then apply various encryption techniques to it. In the first scheme, encryption operations are conducted at the transformation stage and quantization stage of JPEG. As for the second scheme, we add the run/size and value (RSV) pairs’ shuffling operation at JPEG’s entropy coding stage after first scheme’s encryption operations. Performance evaluations using various criteria are conducted to show that the first scheme has better compression efficiency, while the second scheme has better defense ability against the statistical attack.

For joint image compression and encryption schemes, the encryption power and compression efficiency are commonly two contradictory things. In this paper, we propose a new joint image compression and encryption scheme based on a lossy JPEG standard, which aims at encryption power's enhancement, on the premise of maintaining the JPEG's compression efficiency. The proposed scheme is image-content-adaptive, since the secret encryption key is generated from the plain image using the BLAKE2 hash algorithm. Three encryption operations are contained in our scheme, alternating new orthogonal transforms transformation, dc coefficients encryption, and ac coefficients encryption. To save the cost for transmitting different encryption keys each time to decoder for decryption when the plain image changes, we propose embedding the encryption key into the entropy-encoded bitstream of some ac coefficients, and the whole embedding procedure is controlled by another secret key called the embedding key. Extensive experiments are conducted to show that our encryption scheme is JPEG friendly, and has good confusion and diffusion properties. Detailed security analysis is also given to illustrate the proposed scheme's persistence to various cryptanalysis strategies.

In this paper, we conduct an in-depth study on the feasibility of using network coding to ameliorate the content availability of BitTorrent swarms. We first perform mathematical analysis on the potential improvement in the content availability and bandwidth utilization induced by two existing network coding schemes. It is found that these two coding schemes either incur a very high coding complexity and disk operation overhead or cannot effectively leverage the potential of improving the content availability. In this regard, we propose a simple sparse network coding scheme in which both the drawbacks mentioned before are precluded. To accommodate the proposed coding scheme into BitTorrent, a new block scheduling algorithm is also developed based on the original rarest-first block scheduling policy of BitTorrent. Through extensive simulations and performance evaluations, we show that the proposed coding scheme is very effective in terms of improving the content availability of BitTorrent swarms when compared with some existing methods.

Private BitTorrent community is becoming increasingly popular, and generates a huge amount of Internet traffic. In this paper, we present a thorough measurement study on a famous private BitTorrent community, CHDBits. We find that the content of torrents published in this community are highly available, although many torrents may have been released for a very long time, and we also obtain that users in most torrents could download at a high rate. By studying user profiles, we show that many users have participated in multiple torrents, thereby generating a great amount of upload and download traffic. The user profiles also reveal that almost all users maintain a high share ratio, and are willing to contribute to content distribution by spending more time in seeding than in leeching (downloading). Our study suggests that the bandwidths of a user have a significant impact on their behavior. Low bandwidth users are more likely to participate in the torrents with a smaller content size or a higher popularity; compared with low bandwidth users, high bandwidth users tend to participate in more torrents, but spend much less time in seeding.

Video broadcasting is one of the efficient methods in implementing large-scale video-on-demand (VoD) systems. Managing large number of concurrent channels in a video server is the main barrier to implement Harmonic Broadcast (HB) in VoD applications. In this chapter, we propose a new transmission protocol denoted as Harmonic-Based Peer-to-Peer Broadcasting (HPB) to release the burden of HB by dispersing a large portion of workload over a number of clients denoted peer servers. As the bandwidth requirement of each segment in HB is different, we first develop a segment placement algorithm to balance the workload among peer servers. We then study the dynamic nature of peer-to-peer (P2P) paradigm on the design of the system. An analytical model is developed to determine the optimal number of peer servers required for the system under certain level of availability such that the workload of the central server can reach a target level. The results show that the workload of central server can be significantly reduced.

Recently, a chaotic cryptographic scheme based on composition maps was proposed. This paper studies the security of the scheme and reports the following findings: 1) the scheme can be broken by a differential attack with $6+\lceil\log_L(MN)\rceil$ chosen-plaintext, where $MN$ is the size of plaintext and $L$ is the number of different elements in plain-text; 2) the scheme is not sensitive to the changes of plaintext; 3) the two composition maps do not work well as a secure and efficient random number source., 9 pages, 7 figures

Peer-to-peer (P2P) and multicast approaches are two common transmission strategies to provide scalable and cost efficient solutions for video-on-demand (VoD) services. The former approach requires small server resources and provides a negligible delay to users, but the bandwidth requirement inside the network will be rapidly increased when more customers join the video session. On the other hand, if the system simply uses a multicast scheme to deliver a video, customers will experience a noticeable delay before watching the video whereas the overall bandwidth requirement will not be significantly increased. In this paper, a new transmission policy denoted peer-to-peer batching (PPB) policy is proposed to efficiently deliver video data in a large scale VoD system by exploiting the multicast capability of the network and P2P paradigm. To avoid the disruption of services, the fault tolerance and recovery mechanism is also developed for PPB. In addition, in order to further improve the scalability of the system, a distributed PPB (DPPP) is also proposed. We then develop a mathematical model to evaluate the performance of each of our proposed policies analytically. Based on this model, system designers are able to study various design options as well as perform system dimensioning. Both analytical and simulation results show that the proposed scheme achieves better system performance compared with existing schemes.

This paper presents a new collaborative peer-to-peer (P2P) streaming framework for heterogeneous bandwidth capacity of clients. The proposed architecture aims for two primary goals: (1) providing higher streaming quality by making best use of the extra available bandwidth that might exist among heterogeneous clients and (2) providing robustness and resilience to high churn rate of peers by introducing redundancy, both in network paths (multisender overlay) and data (multilayered video content). For achieving these goals, we employ a gossip-based data-driven scheme for partnership formation and layered video coding for bandwidth adaptivity. To solve multilayer bitstream allocation problem, we proposed two algorithms, namely optimized transmission policy and graceful degradation scheme algorithms. The proposed system has a complete self-regulation and in a decentralized fashion. Extensive simulations show that the proposed system achieves higher quality of service through peer-assisted streaming and layered video coding. The results also show that the system outperforms some previous schemes in system overhead and reliability for dynamic node behavior.

Transmission of compressed video is very sensitive to channel error. The use of resynchronization marks is an efficient method in improving the error resilient performance of a video stream in error-prone environment. In this paper, a smart macroblock rearrangement (SMR) method is proposed to enhance the performance of the resynchronization mark insertion technique for intracoded frames in wireless video transmission. The proposed method makes use of content analysis to rearrange and encode macroblocks between adjacent resynchronization marks. Experiments using the SMR method in both H.263+ and H.264 codecs show that the proposed method outperforms some existing algorithms in both PSNR performance and visual quality.

To support large-scale Video-on-Demand (VoD) services in a heterogeneous network environment, either a replication or layering approach can be deployed to adapt the client bandwidth requirements. With the aid of the broadcasting and caching techniques, it has been proved that the overall performance of the system can be enhanced. In this paper, we explore the impact on the broadcasting schemes coupled with proxy caching and develop an analytical model to evaluate the system performance in a highly heterogeneous network environment. We develop guidelines for resources allocation, transmission strategies as well as caching schemes under different system configurations. The model can assist system designers to study various design options as well as perform system dimensioning. Moreover, a systematic comparison between replication and layering is performed. From the results, it can be seen that the system performance of layering is better than that of replication when the environment is highly heterogeneous even if the layering overhead is higher than 25%. In addition, it is found that the system blocking probability can be further reduced by exploring the broadcast capability of the network if the proxy server cannot store all the popular videos.

Video broadcasting has been proved to be an efficient technique to increase the scalability of a video-on-demand (VoD) system. In this paper, we address the problems in providing interactive functions for VBR encoded videos in a broadcast VoD system. A traffic smoothing scheme is proposed to support the VCR functions in delivering VBR videos over CBR channels by the staggered broadcasting protocol. By introducing a small buffering delay, the customers are able to join back to the broadcasting groups after the interactive functions. A system model is then developed to determine the optimal parameters such that the system can meet the delay requirement as well as provide the expected quality of service to the customers. The results show that the proposed system framework is very efficient in terms of bandwidth requirement and buttering delay to provide interactive VoD services.

This paper reports security problems with improper implementations of an improved version of FEA-M (fast encryption algorithm for multimedia). It is found that an implementation-dependent differential chosen-plaintext attack or its chosen-ciphertext counterpart can reveal the secret key of the cryptosystem, if the involved (pseudo-)random process can be tampered (for example, through a public time service). The implementation-dependent differential attack is very efficient in complexity and needs only $O(n^2)$ chosen plaintext or ciphertext bits. In addition, this paper also points out a minor security problem with the selection of the session key. In real implementations of the cryptosystem, these security problems should be carefully avoided, or the cryptosystem has to be further enhanced to work under such weak implementations., Comment: 8 pages, elsart.cls

Video broadcasting is one of the feasible solutions to implement a large-scale video-on-demand (VoD) system. Nevertheless, it is still an open issue for the provision of continuous VCR functions in a delay insensitive broadcast VoD system. In this paper, we propose to jointly optimize an active buffer management scheme with contingency channels to support the VCR functions in an efficient protocol called partitioned broadcasting. We develop a greedy channel management scheme by exploiting the property of the broadcasting protocol such that the system bandwidth capacity can be fully utilized. Incorporating the channel management scheme with the partitioned video broadcast, the VoD system not only provides delay insensitive services but also handles all the interactive requests. Extensive simulation results demonstrate that the partitioned broadcasting system outperforms the traditional system based on the staggered broadcasting protocols. It is found that 20 broadcasting channels and 10 contingency channels are sufficient to support on average 720 customers for a single video with less that one second start-up delay and all types of VCR functions.

In this paper, a two-tier hierarchical network architecture is exploited to provide true video-on-demand (VoD) services using double-rate (DR) batching in multicast environment. In the proposed system, new customers will be grouped together by the local server with the DR batching scheme and then be served by the multicast backbone network. Two scheduling policies are developed to serve customers at the local batching servers. The results show that the hierarchical VoD system can greatly reduce the resources requirement compared with the centralized approach. In addition, in order to secure the multicast channels for the new multicast groups, the backbone channel reservation algorithm that is similar to the look-ahead scheme [Multimedia Systems 3 (1995) 137] is proposed. If there are 100 videos and 500 backbone multicast channels, the system is able to support 0.2 requests/s with less than 7% admission blocking probability.

Data sharing is a feasible solution to support a large-scale video-on-demand (VoD) system, however, it is still an open issue to provide a full set of continuous interactive functions in such an environment that a single channel is used to serve a group of customers. In this paper, we first investigate the performance of client buffer management and its hybrid use with contingency channels for providing VCR functionality in a staggered broadcast VoD system. Results show that directly combining the two methods may not gain any advantages since the resources are not fully utilized. To tackle this problem, a greedy algorithm is proposed to efficiently manage the contingency channels such that the system performance can be significantly improved by exploiting the property of the staggered broadcast scheme and the use of multiple loaders in the receiver. Simulation results show that the proposed greedy system can efficiently provide a full set of VCR functions with satisfied user performance in a broadcast VoD system.

In this paper, we propose a method called z-characterization for computing the deterministic bounds of an aggregated MPEG stream at frame level. Traditional deterministic characterization methods like empirical envelope generally suffer from the drawback of high computation complexity. In our approach, the I, P and B sub-traces of an MPEG trace will be characterized independently such that they possess their own empirical envelopes. By exploiting the periodic group-of-pictures (GOP) structure of MPEG video, the I, P and B sub-envelopes can act as building blocks for computing the characterization of the aggregate stream in real-time. Experimental results show that our proposed characterization closely bounds the empirical envelope in both homogenous and heterogeneous multiplexing scenarios. Copyright © 2004 John Wiley & Sons, Ltd.

In this paper, the authors treat the key frame extraction problem from a viewpoint of shot reconstruction. As a result, a novel criterion called shot reconstruction degree (SRD) is proposed for key frame selection based on the degree of retaining motion dynamics of a video shot. Compared with the widely used fidelity criterion, the key frame set produced by SRD can better capture the detailed dynamics of the shot. Using the new SRD criterion, a novel inflexion-based key frame selection algorithm is developed. Simulation results show that the new algorithm results in good performance in terms of both fidelity and shot reconstruction degree.

In this paper, a new cut detection algorithm with constant false-alarm ratio (CFAR) is proposed for video segmentation. In our method, a theoretical threshold determination strategy using the non-parameter based CFAR processing technique is developed to achieve a controllable precision as well as an evaluative recall performance for video cut detection. Simulation results show that this algorithm leads to very good detection performance as compared to the existing techniques.

Broadcasting is an efficient transmission scheme to provide on-demand service for very popular movies in a multicast environment. In this paper, a comparative study is first performed to evaluate various broadcasting protocols in terms of maximum waiting time, client buffer requirement and receiver bandwidth. It is found that some existing broadcasting schemes are not practical to provide a small delay video-on-demand (VoD) service if the client buffer size is not large enough. It is shown that the staggered [1] and skyscraper [3] protocols are the only feasible solutions to support an insensitive delay VoD system with limited client buffer and receiver bandwidth. Two first segment partition schemes are then proposed to further reduce the maximum waiting time of these two broadcasting schemes. The results show that if 15 min of video data can be stored in the buffer, Skyscraper with our proposed schemes can serve the customers within 10 s using 16 video channels. For Staggered broadcasting with our schemes, the maximum waiting time can also be reduced from 7.5 min to less than 1 min.

This paper reports on a new key frame based video abstraction method. With our method, a video sequence is first segmented into a number of video shots. Several key frames are selected in each shot using a dynamic selection technique. For these key frames, a motion-based clustering algorithm is applied so that key frames in the same cluster are alike in sense of motion compensation error, while those from different clusters are quit dissimilar. Then a novel cluster-based coding scheme is developed for efficient representation of the key frames. Simulations show that the proposed method can select key frames according to the dynamics of a video sequence and abstract the video with different levels of scalability.

In providing video-on-demand services in multicast environment, a broadcasting technique like skyscraper is very efficient for serving a very popular video in terms of resource requirement. However, a multicasting method like patching will achieve better performance if the video is not popular enough. Since there may not be a clear distinction between very popular and popular videos, an analytical model is developed in this paper to select an appropriate delivery scheme for the videos according to both the popularity of videos and the customer reneging behavior. The result shows that not only is the overall bandwidth of the system minimized, but a preset quality of service is also provided for each customer when using our proposed scheme.

The adaptive batching technique is shown to have better performance than the static scheme in terms of total bandwidth requirement and customer reneging probability in multicast video-on-demand (VoD) systems. In this paper, we first analyze the performance of providing VCR functions in the multicast VoD system using adaptive batching. The result shows that the system may not take any advantage from the adaptive approach if VCR operations are incorporated. In view of this, we then explore the buffer reservation and VCR resume delay to further improve the adaptive system. The trade-off among the buffer size, resume delay, and stream requirement is extensively investigated. It is found that a 30-s resume delay or 20% buffer reservation can significantly reduce the batching stream requirement in the adaptive multicast VoD system.

A new delivery strategy is proposed for a video-on-demand system to allocate transmission resources according to the popularity of videos. A video is delivered to customers through one of three channels, namely broadcast, multicast and unicast, depending on whether the video is very hot, hot or cold, respectively. An algorithm is developed to select the appropriate delivery channel for the videos so that not only the overall bandwidth of the system is minimized but also a preset quality of service is provided for each customer. An analytical model is also developed to evaluate the bandwidth requirement of the whole system with VCR functionality. The result shows that a significant bandwidth reduction can be achieved when using our proposed delivery strategy.

This paper presents a refined version of the M/G/~ busy-server process described in IEEE J. Select. Areas Commun., 16(5) (1998) 733-748 for VBR video modelling, with emphasis on a refined fitting approach of marginal distribution. First we suggest using normal mixture distribution instead of Gamma-Pareto distribution to model the marginal distribution for greater flexibility and accuracy. Second, we retune the parameter value of the Poisson input process to ensure smooth distribution transformation. Experimental results indicate that our model gives closer estimate to the empirical cell loss behaviour than the original model. Also, its performance is more consistent than other uni-distribution models like Gamma and lognormal, when fitting a wide variety of video sequences.

In this paper, an adaptive algorithm is developed for providing true video on demand (VoD) services in a multicast environment. In conventional batching schemes, the batching time of the system is fixed and the performance of such static schemes is highly dependent on the selection of the batching time. If the batching time is wrongly estimated, the performance of the system will be greatly degraded. Our algorithm tries to dynamically find the optimal batching time by the newly updated arrival rate so as to minimize the bandwidth requirement. The results show that the system performance of the adaptive approach is always better than the static scheme in terms of total bandwidth requirement and customer reneging probability, especially in using long batching time for the high arrival rate.

In this paper we study the performance of ATM multiplexing of homogeneous MPEG video sources. A source scheduling method is developed to improve the performance of ATM multiplexer for MPEG video sources. Simulation results show that the level of burstiness for the aggregated MPEG traffic is reduced and the network performance is enhanced. Based on the rationale of the source scheduling method, a simple but efficient bandwidth allocation algorithm is also derived for connection admission of MPEG video in an ATM multiplexer. Copyright © 2001 John Wiley & Sons, Ltd.

In this article, a bandwidth estimation model for VBR video transmission is proposed. This model refines the work mentioned in Zhang et al. (Z.L. Zhang, J. Kurose, J.D. Salehi, D. Towsley, Smoothing, statistical multiplexing, and call admission control for stored video, IEEE Journal on Selected Areas in Communications, 15(6) (1997) 1148-1166.) to strengthen the scalability under correlated traffic arrivals. In this model, we attempt to capture the characteristics of the two levels of bit-rate variation by defining two modelling layers and refining the definition of service robustness. Results obtained from this model have shown its strong scalability on different levels of variation.

Multicast delivery is one of the solutions to reduce the cost in a large video-on-demand (VoD) system. However, multicast transmission makes much more difficult the implementation of interactive functions for individual users and introduces start-up delays for the users, which contradicts the idea of on-demand services. In this paper, we first try to explore and evaluate the performance of different multicast VoD systems. A new scheme called single-rate multicast double-rate unicast (SRMDRU) is then developed to minimize the system resources for supporting full VCR functionality in a multicast VoD system. This scheme also allows multicast systems to support true VoD services so customers can be served as soon as the system receives the requests. Computer simulations show that the multicast systems using the SRMDRU scheme perform much better than other multicast systems in terms of system blocking probabilities.

Packet loss is a critical problem for video transmission on packet-switched networks. An error compensation method called the modified boundary matching algorithm is developed for recovering lost video due to packet loss at the video decoder. Simulation results demonstrate that the proposed method preserves good image quality even when the cell loss rate is very high.

To achieve an optimum transmission over a noisy wireless channel, both the source coding and network should be jointly adapted. An acceptable video quality in wireless environ‐ ment can be obtained by the adjustment of parameters in video codec and wireless network. For the former, people have proposed many error resilient video encoding algorithms to en‐ hance the robust performance of the compressed video stream in wireless networks. These algorithms can be divided into three categories: 1) error detection and error concealment al‐ gorithms used at video decoder of wireless receiver; 2) error resilient video encoding algo‐ rithms located at video encoder of wireless transmitter; 3) robust error control between video encoder and decoder based on 1) and 2). Fig.1 summarizes different techniques at dif‐ ferent parts of a wireless video transmission system.

When applying conventional standard video codecs in wireless video applications, error resilience and coding efficiency are the two main issues need to be considered. Since it is difficult to corroborate robust quality of service (QoS) in wireless networks, transmitted video packets are sometime lost or corrupted due to fading and shadowing effect of wireless channel. Providing robust video transmission in wireless packet-switched networks is therefore a challenging task as compressed video is very vulnerable to channel error. In recent years, many error resilient tools have been proposed to enhance the robust performance of video transmission in wireless environment (Chen et al., 2008)(Stockhammer et al., 2003) (Stockhammer et al., 2005) (Vetra et al., 2005) (Wang et al., 2000) (Wiegand et al. 2003). Coding efficiency is one of the important issues to be taken into account for the limited bandwidth of wireless networks (Etoh and Yoshimura, 2005). To achieve a robust video transmission over wireless channels, the video codec on one hand should have supreme error resilient performance, on the other hand, it should also maintain a good coding efficiency by limiting the overhead information introduced by the error resilient tools. Hence, a good compromise between the error resilience performance and coding efficiency should be made. Interactive error control is one of the effective error resilient techniques adopted in video codec. In this category, some error resilient techniques based on data hiding are proposed (Zeng, 2003) (Yilmaz and Alatan, 2003) (Kang and Leou, 2005). In such techniques, the important information for error concealment is extracted and embedded into video bitstream at the video encoder. When some packets are lost or corrupted, their corresponding embedded data at proper positions can enhance the error concealment effect at the video decoder. Although data hiding methods can obtain satisfied error resilient effect, their notable increase of bits overhead is disadvantageous for coding efficiency. Since the principle of embedding important information (Yin el al., 2001) they adopted modifies the original AC coefficients, not only video quality is degraded, but also coding overhead will be increased significantly. In wireless channels, as the transmission rate is limited, an obvious increase on coding overhead results in inevitable delay. Moreover, in wireless

Recently, a chaos-based image encryption algorithm called MCKBA (Modified Chaotic-Key Based Algorithm) was proposed. This paper analyzes the security of MCKBA and finds that it can be broken with a differential attack, which requires only four chosen plain-images. Performance of the attack is verified by experimental results. In addition, some defects of MCKBA, including insensitivity with respect to changes of plain-image/secret key, are reported., 10 pages, 4 figures

Recently, Yen et al. presented a new chaos-based cryptosystem for multimedia transmission named ''multimedia cryptography system'' (MCS). No cryptanalytic results have been reported so far. This paper presents a differential attack to break MCS, which requires only seven chosen plaintexts. The complexity of the attack is O(N), where N is the size of plaintext. Experimental results are also given to show the real performance of the proposed attack.

We investigate the video assignment problem of a hierarchical Video-on-Demand (VOD) system in heterogeneous environments where different quality levels of videos can be encoded using either replication or layering. In such systems, videos are delivered to clients either through a proxy server or video broadcast/unicast channels. The objective of our work is to determine the appropriate coding strategy as well as the suitable delivery mechanism for a specific quality level of a video such that the overall system blocking probability is minimized. In order to find a near-optimal solution for such a complex video assignment problem, an evolutionary approach based on genetic algorithm (GA) is proposed. From the results, it is shown that the system performance can be significantly enhanced by efficiently coupling the various techniques.

This paper studies the security of a recently-proposed MPEG-video encryption scheme based on secret Huffman tables. Our cryptanalysis shows that: 1) the key space of the encryption scheme is not sufficiently large against divide-and-conquer (DAC) attack and known-plaintext attack; 2) it is possible to decrypt a cipher-video with a partially-known key, thus dramatically reducing the complexity of the DAC brute-force attack in some cases; 3) its security against the chosen-plaintext attack is very weak. Some experimental results are included to support the cryptanalytic results with a brief discuss on how to improve this MPEG-video encryption scheme.

This paper proposes the software optimization for implementing AVS-P3 realtime on ARM 9. The optimization for embedded systems has been recognized as a key issue in improving cost as well as performance. In this work, we describe our experience in optimizing AVS audio decoder based on ARM9. We mainly optimize the inversed IntMDCT, CBC and dequantization modules. The test result shows that the decoding speed improves 10 times than the original AVS audio decoder decoding stereo wave signal with the 128 kbps bitrate and 48 KHz sampling rate. Meanwhile, the memory space is reduced from 130.78 KB to 59.91 KB, achieved 54.2% improvement.

Recently, a chaos-based image encryption scheme called RCES (also called RSES) was proposed. This paper analyses 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 to succeed an attack. 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/chosen-plaintext attacks. The insecurity of RCES is due to its special design, which makes it a typical example of insecure image encryption schemes. A number of lessons are drawn from the reported cryptanalysis of RCES, consequently suggesting some common principles for ensuring a high level of security of an image encryption scheme.

In recent years secret permutations have been widely used for protecting different types of multimedia data, including speech files, digital images and videos. Based on a general model of permutation-only multimedia ciphers, this paper performs a quantitative cryptanalysis on the performance of these kind of ciphers against plaintext attacks. When the plaintext is of size MxN and with L different levels of values, the following quantitative cryptanalytic findings have been concluded under the assumption of a uniform distribution of each element in the plaintext: (1) all permutation-only multimedia ciphers are practically insecure against known/chosen-plaintext attacks in the sense that only O(log"L(MN)) known/chosen plaintexts are sufficient to recover not less than (in an average sense) half elements of the plaintext; (2) the computational complexity of the known/chosen-plaintext attack is only O(n.(MN)^2), where n is the number of known/chosen plaintexts used. When the plaintext has a non-uniform distribution, the number of required plaintexts and the computational complexity is also discussed. Experiments are given to demonstrate the real performance of the known-plaintext attack for a typical permutation-only image cipher.

Skyscraper broadcast (SB) is one of the effective ways to provide a scalable solution for video-on-demand (VoD) services. Originally, SB was only designed for supporting a near-VoD service to clients. In this paper, we propose a new transmission scheme called skyscraper-based peer-to-peer broadcasting (SPB) to realize a true-VoD service in SB. It is accomplished by shifting the duty of the first segment transmission to the clients in peer-to-peer (P2P) manner. It is found from the results that the proposed scheme is superior to the existing strategies that the transmission cost of the system and that of the central server can be reduced up to 7% and 30% respectively.

To support large-scale video-on-demand (VoD) services, many transmission schemes such as data broadcasting and proxy caching have been developed to minimize the resources requirement and enhance the system scalability. However, most of the previous works mainly focused on providing the VoD services in a homogeneous environment. In this paper, we investigate a feasible solution for building an efficient hierarchical VoD system using proxy caching coupled with broadcasting and appropriate coding schemes in heterogeneous environment so as to minimize the system transmission cost. By developing a performance model in this paper, system designers can study how various techniques for VoD can be organized to maximize the efficiency of the system. From the results, it can be seen that the system performance can be greatly enhanced by efficiently coupling various techniques.

Peer-to-Peer (P2P) communications have become a popular alternative solution to provide large-scale video-on-demand (VoD) services. Recent approaches are designed for streaming applications in a unicast infrastructure. As the successful deployment of IP broadcast delivery, the system could have a further improvement when broadcasting scheme can be coupled with P2P paradigm. In this paper, we develop a possible solution for building a VoD system using existing broadcasting protocol coupled with cooperative clients in multicast environment. The objective of this work mainly focuses on addressing one design issue in such framework: reliability. An analytical model is developed to determine the minimum number of cooperative clients required for the system. The results showed that 60 peers, each of which has the availability of 0.4, are enough to leverage the workload of the central server up to 95%, when the startup delay of the system is 10 minutes.

Recently, peer-to-peer (P2P) overlay networks have become popular and many P2P applications such as file sharing and content distribution have been introduced. Naturally, P2P cooperative caching schemes for streaming were introduced. However, these approaches manifest inefficiency of cache utilization due to inappropriate cache replacement algorithms, and no consideration of dynamic membership changes of peer nodes. In this paper, we investigate an efficient cooperative caching mechanism for VOD streaming service over P2P overlay networks. The target of the system is to provide low-latency and high-quality services by virtue of pees' collaboration. The storage and replacement of caching content are based on segment-based strategy. And a utility-based fine-grained cooperative cache (DUFC) policy was proposed for cache replacement. We demonstrate the effectiveness of the proposed scheme and compare with traditional LRUF scheme through extensive simulation experiments over large, Internet-like topologies.

Multicast and peer-to-peer (P2P) are two common transmission strategies to provide scalable and cost efficient solutions for video-on-demand (VoD) services. It is noted that a native P2P mechanism requires small server resources and provides an insensitive delay to users. However, the bandwidth requirement inside the network is rapidly increased when more customers joins the video session. On the other hand, if the system simply uses a multicast scheme to deliver the video, the customers have to wait for a noticeable delay before watching the videos whereas the overall bandwidth requirement will not be significantly increased. In this paper, a new transmission policy denoted peer-to-peer batching (PPB) policy is proposed to exploit the multicast capability of the network and P2P paradigm to efficiently deliver video data to the clients. Our analysis shows that the proposed PPB scheme achieves better system performance when compared with Patching (a native multicast system) and DirectStream (a native P2P system).

Recently Lin et al. proposed a method of using the underdetermined BSS (blind source separation) problem to realize image and speech encryption. In this paper, we give a cryptanalysis of this BSS-based encryption and point out that it is not secure against known/chosen-plaintext attack and chosen-ciphertext attack. In addition, there exist some other security defects: low sensitivity to part of the key and the plaintext, a ciphertext-only differential attack, divide-and-conquer (DAC) attack on part of the key. We also discuss the role of BSS in Lin et al.'s efforts towards cryptographically secure ciphers., 8 pages, 10 figures, IEEE format

Live media streaming applications are increasing dramatically on the Internet such as IPTV, distance learning, video conference etc. Meanwhile, layered transmission is a promising solution to video streaming over the heterogeneous Internet. This paper presents LSONet, which leverages the advances in both the field of media compression, i.e., layered video coding, and the field of networking, i.e., application-level overlay networking. The purposes are, respectively, to obey the delay requirement, to improve bandwidth efficiency and to adapt to network jitter. The proposed system is completely self-organizing, and it can adapt to network dynamics in a fully distributed fashion. Extensive simulations have been performed. The results show that the system outperforms previous scheme in resource utilization and more robust and resilient for network fluctuation, which demonstrate that the proposed architecture and the associated protocol are well-suited for quality adaptive live streaming applications

Streaming layered video is one of the possible solutions in providing large-scale video-on-demand (VoD) services in a heterogeneous network environment. In this paper, we analyze the performance of a hierarchical VoD system using layered videos in broadcast environment, in which we not only store some of the popular videos in the proxy server but also broadcast some of the video layers to the customers so as to minimize the blocking probability of the system. By deriving a performance model, we analyze the impacts of different parameters such as the proxy size, the number of broadcasting channels for each layer and the bandwidth reserved for broadcasting on the system performance. From the results, it can be seen that the system performance in terms of blocking probability can be greatly enhanced when using video broadcasting protocols in a hierarchical VoD system.

Providing media streaming services over a peer-to-peer (P2P) network has attracted much attention in recent few years. In this paper, we focus on a tree structured P2P network for live media streaming. In our proposed P2P framework, the Prim-Dijkstra algorithm is used to construct the network spanning tree. A new fast parent searching method based on network triangle inequality is then developed for the newly arrived peers to join the P2P media streaming network. Simulation results show that the complexity of the parent searching procedure is greatly reduced using the proposed method.