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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.

A joint image compression and encryption scheme based on JPEG is proposed.Encryption is mainly realized at JPEGs transformation stage.The scheme is format compliant to JPEG with tunable encryption parameters.Good encryption and compression performances can be achieved simultaneously. In this paper, we propose a novel joint image compression and encryption scheme based on JPEG standard. We realize image encryption at JPEGs transformation stage. Instead of only using 88 discrete cosine transform (DCT) for transformation, we generate new orthogonal transforms by embedding an extra rotation angle of to different stages butterflies in 88 DCTs flow-graph, and then apply them alternatively for transformation according to a predefined secret key. By carefully controlling the number of rotation angles embedded, the quality control of encrypted images can also be achieved. The encryption algorithm is further enhanced by performing block permutation before the entropy encoding stage. Extensive experiments have been conducted to show the good protection and compression performance of our encryption schemes. Finally, a detailed security analysis is provided to show the encryption schemes resistance to various cryptanalysis methods, such as brute-force attack, key sensitivity analysis, replacement attack and statistical attack.

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.

In this paper, we propose a novel joint image compression and encryption technique where an annoying image can still be recovered even without the encryption key. Our work is based on JPEG standard. By embedding encryption algorithm at the transformation stage, we realize image encryption and compression together with controllable image quality. Instead of using the 8×8 discrete cosine transform (DCT) alone for transformation, we develop new orthogonal transforms by introducing sign-flips into the butterflies of DCT's flow-graph structure, and then employ them alternatively in JPEG's transformation stage according to a secret key. By carefully selecting the butterflies for sign-flipping, we can control the visual quality of the encrypted images. Finally, a detailed security analysis of our proposed encryption algorithm is presented to show its resistance to various attacks, such as cryptographic attack, replacement attack and statistical model-based attack.

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.