基于H.264/SVC的视频加密技术研究

随着网络的不断普及和发展,视频数据在网络中有了越来越多的应用,随之也提出了视频安全的问题,通过视频加密可以很好地解决此问题。文中分析了目前主流的H.264SVC标准所采用的可分级视频编码技术,根据视频分级编码特点选取关键信息进行分层加密,实现不同级别的视频加密。同时,所提方案采用了序列密码进行加密,具有较高的安全性。试验结果表明:该方案具有安全性高、复杂度适中、实时性好等特点。     

Bitstream-Oriented Protection for the H.264/Scalable Video Coding (SVC)

The newly standardized H.264/SVC enable multimedia suppliers to provide video bitstream with temporal, spatial and quality scalabilities to meet various needs of end users. Its bitstream scalability characteristic is also especially suitable for multimedia applications under merged heterogeneous networks with different network protocols, capacities and throughputs. Although the network environment, to some extent, provides security protection against the illegal users, it is not enough to protect against the authorized users from digesting contents beyond its authorization. Hence the issue of content protection for the H.264/SVC has aroused researchers’ interests in recent years. In this paper, we present an efficient bitstream-oriented protection scheme for the H.264/SVC in a compression friendly and format compliant manner. The encryption is implemented on the Network Abstraction Layer (NAL) unit level. To improve the computational efficiency as well as to provide sufficient security, selective cryptographic algorithms with different computation cost are employed for different content level of SVC according to its significance. The I slice NAL units from the base layer of SVC bitstream are encrypted with the symmetric AES algorithm in Cipher Block Chaining mode. And the other NAL units are protected by simplified XOR cipher. Furthermore, a robust key management (key generation and distribution) mechanism is also discussed in this paper. The security analysis and simulation results further verify that the proposed methods can effectively protect the H.264/SVC bitstream at low computational cost.     

Robust multipoint and multi-layered transmission of H.264/SVC with Raptor codes

The scalable extension of the H.264 Advanced Video Coding (AVC) standard called Scalable Video Coding (SVC), or H.264/SVC, provides scalable video streams which are composed by a base layer and one or more enhancement layers. Enhancement layers may improve the temporal, the spatial or the signal-to-noise ratio resolutions of the content represented by the lower layers. One of the applications of this video coding standard is related to point-to-multipoint video distributions in both wired and wireless communication systems, where packet losses contribute to the degradation of the user’s Quality of Experience. Designed for the transmission of data over Binary Erasure Channels (BEC), Raptor codes are a Forward Error Correction (FEC) mechanism that is gaining popularity for Internet Protocol Television (IPTV) applications due to their small decoding complexity and reduced overhead. This paper evaluates the quality enhancements introduced by the integration of several H.264/SVC layers with a Raptor coding protection scheme. Our goal is to improve the distribution of video over loss prone networks in terms of rate-distortion performance by assessing several alternative packetization options and protection schemes.     

Adaptation–aware encryption of scalable H.264/AVC video for content security

Data encryption is one of the key information security technologies used for safeguarding multimedia content from unauthorised access and manipulation in end-to-end delivery and access chains. This technology, combined with the appropriate cryptographic methods, effectively prevents the content against malicious attacks, so as to protect its authenticity as well as integrity. While encryption-based security is ensuring the authorised consumption of the multimedia content, content adaptation technologies have the primary goal of providing means for wider dissemination of the content across diverse networks, devices and users, and thus enriching user satisfaction and experience of the delivered content within a given set of usage environment constraints. Traditionally, protected contents can only be adapted at trusted adaptation engines residing between the source and end-users, since they have to be fully decrypted before performing the necessary adaptation operations. The drawback of such a process is that it significantly limits the availability and flexibility of adaptation engines applicable for adapting protected contents on the fly. Thus, this paper proposes a novel scalable H.264/advanced video coding (AVC)-compatible video encryption technique, which is also transparent to adaptation engines in an end-to-end video delivery scenario. The proposed technology relies on keeping syntax elements required for performing the adaptation operations clear (i.e., not encrypted). The effectiveness of the proposed technique has been successfully verified in scenarios, where both conventional joint scalable video model (JSVM) bit stream extracting and random packet dropping mechanisms are used.     

Transparent encryption with scalable video communication: Lower-latency,CABAC-based schemes

Selective encryption masks all of the content without completely hiding it, as full encryption would do at a cost in encryption delay and increased bandwidth. Many commercial applications of video encryption do not even require selective encryption, because greater utility can be gained from transparent encryption, i.e. allowing prospective viewers to glimpse a reduced quality version of the content as a taster. Our lightweight selective encryption scheme when applied to scalable video coding is well suited to transparent encryption. The paper illustrates the gains in reducing delay and increased distortion arising from a transparent encryption that leaves reduced quality base layer in the clear. Reduced encryption of B-frames is a further step beyond transparent encryption in which the computational overhead reduction is traded against content security and limited distortion. This spectrum of video encryption possibilities is analyzed in this paper, though all of the schemes maintain decoder compatibility and add no bitrate overhead as a result of jointly encoding and encrypting the input video by virtue of carefully selecting the entropy coding parameters that are encrypted. The schemes are suitable both for H.264 and HEVC codecs, though demonstrated in the paper for H.264. Selected Content Adaptive Binary Arithmetic Coding (CABAC) parameters are encrypted by a lightweight Exclusive OR technique, which is chosen for practicality.     

An interoperable delivery framework for scalable media resources - seamless content delivery in the future mobile internet

In this article an interoperable framework for the delivery of scalable media resources (e.g., in the standardized scalable video coding format) is presented. The framework provides support for video on demand as well as multicast streaming, and performs efficient, generic, and interoperable adaptation of streamed content based on MPEG- 21 Digital Item Adaptation. The server as well as the clients of the streaming framework implement the MPEG Extensible Middleware and utilize the MPEG Query Format for querying the available media resources. The framework has been fully integrated into the VLC media player. The architecture for both VoD and multicast is presented in detail. Finally, a comparison in terms of performance of the generic MPEG-21 metadata-based adaptation approach to an SVC-specific adaptation approach is provided.     

云环境下安全的可验证多关键词搜索加密方案

云计算的高虚拟化与高可扩展性等优势,使个人和企业愿意外包加密数据到云端服务器。然而,加密后的外包数据破坏了数据间的关联性。尽管能够利用可搜索加密(SE)进行加密数据的文件检索,但不可信云服务器可能篡改、删除外包数据或利用已有搜索陷门来获取新插入文件相关信息。此外,现有单关键词搜索由于限制条件较少,导致搜索精度差,造成带宽和计算资源的浪费。为了解决以上问题,提出一种高效的、可验证的多关键词搜索加密方案。所提方案不仅能够支持多关键词搜索,也能实现搜索模式的隐私性和文件的前向安全性。此外,还能实现外包数据的完整性验证。通过严格的安全证明,所提方案在标准模型下被证明是安全的,能够抵抗不可信云服务器的离线关键词猜测攻击(KGA)。最后,通过与最近3种方案进行效率和性能比较,实验结果表明所提方案在功能和效率方面具有较好的综合性能。     

面向云存储的安全密文访问控制方案

存储在云端服务器中的敏感数据的保密和安全访问是云存储安全研究的重要内容.针对真实的云存储环境中云服务提供商不可信的情况,采用基于属性的加密算法,提出了一种安全、高效、细粒度的云存储密文访问控制方案.与现有方案相比,该方案在用户撤销时,通过引入广播加密技术,使得撤销用户即使和云服务提供商共谋,也不能对私钥进行更新,保证了数据的安全性;方案将大部分密文重加密和用户私钥更新工作转移给云服务提供商执行,在保证安全性的前提下,降低了数据属主的计算代价;另外该方案还可支持多用户的同时撤销.最后分析了方案的安全性和计算复杂性,并测试了用户撤销时的运行效率.     

H.264/SVC vs. H.264/AVC video quality comparison under QoE-driven seamless handoff

This paper studies the impact of mobility management and seamless handover mechanisms on the perceived quality of video streaming applications. A seamless handoff scheme is proposed that incorporates IEEE 802.21 Media Independent Handover framework and a QoE-driven rate adaptation scheme, for both scalable and single layer coding. Quality of Experience (QoE) has been considered as an important parameter for network selection. The proposed scheme has been implemented and evaluated in a real test-bed network. Objective and subjective quality evaluation measurements for both H.264/AVC and H.264/SVC have been carried out. Through experimentation, QoE driven mobility of video streaming can be better maintained with H.264/SVC under the combined seamless handoff and rate adaptation functionality.