摘要
随着数字技术和互联网工业的快速发展,越来越多的多媒体内容能够通过网络进行发布和传输。许多类型的多媒体数据采用了可伸缩性编码,把原始内容根据不同的准则编码成在质量、空间、时间上渐进的形式,从而能够有选择地丢弃码流中的部分数据来适应当前的带宽条件以及设备的处理和显示能力。另一方面,数字内容极容易复制的特性使得多媒体内容的盗版成为非常严重的问题,由此产生的DRM系统是管理数字内容的授权许可和访问控制的一整套技术。
本文以JPEG 2000和Motion JPEG 2000为实例,为可伸缩性编码的多媒体内容设计了一个“所见即所购”的DRM原型系统。
首先,我们提出了一种与原码流语法兼容、并保持其可伸缩性的加密方案。语法兼容使普通的播放器也可以对加密码流正常解码而不会造成崩溃;如果合理选择加密范围就可以为免费用户提供原始内容的预览。在加密码流中保持原码流的所有可伸缩性使得网络传输路径上的某些处理结点能够根据需要直接对加密码流进行转码,得到适合实际需要的子码流,这个过程既不需要解密密钥,也不要求网络结点是受信任的。这种特性可以称为“一次加密,多种方式解密”。和其它一些有代表性的方案相比,我们的加密方案具有精细的可伸缩性粒度支持,优越的运算速度,良好的比特错误弹性,以及可以忽略的存储空间开销。
然后,我们提出了一种通用、灵活而便捷的密钥管理方案。我们把所有可伸缩性划分为两大类,分别用全序集和偏序集表示。整个多媒体内容就表示为所有全序集和偏序集的笛卡尔积,它仍然为一个偏序集,可以用具有单个根顶点的Hasse图表示。对可伸缩性多媒体的访问控制就等价于对这个偏序集的访问控制。借助一种基于散列函数的密钥推导方法,每个顶点的访问密钥可以由它的父顶点密钥和一些公开辅助信息生成,而散列函数的单向性保证了从所有子顶点密钥也无法得到父顶点密钥。这样,原始码流只需要被加密一次,用户可以自由选择不同可伸缩性参数组合对应的定制版本,每个版本只需要一个子根顶点密钥和相关的公开辅助信息就可以推导出所有数据结点的解密密钥。这种特性可以称为“一次保护,多种方式访问”。
最后,综合上述的加密方案和密钥管理方案,我们基于微软的WMRM框架实现了自己的DRM原型系统。其中,用户根据定制版本“按需”支付费用,对于用户的每次访问请求,DRM服务器只要发送一个访问密钥,其它密钥都可以由用户端DRM模块使用一些公开辅助信息生成。DRM服务器不要求有很强的存储和处理能力,大大提高了它的稳定性和可访问性。
With rapid advances of digital technologies and the Intemet industry,more and more multimedia contents are released and distributed over the Internet.Many types of multimedia data are encoded in a scalable manner,i.e.,the original contents are encoded with respect to various criterions into a progressive manner in quality,space,or time. This allows part of the codestream to be discarded to fit into the current channel bandwidth or the device's processing and display capability.On the other side,the fact that digital contents are very easy to copy makes piracy across the Internet a vital problem. This gives birth to the DRM system,a suite of technologies that manages licensing and access control of digital contents.
In this paper we design a"What You See Is What You Buy" DRM prototype system for scalable multimedia contents,exemplified by JPEG 2000 and Motion JPEG 2000.
We first propose a syntax-compliant encryption scheme that fully preserves the scalabilities of the original multimedia content.Syntax compliance allows a normal player to successfully decode the cipherstream,especially without being crashed.If selected parts of the codestream get properly encrypted,users may be able to get a free preview of the original content.With all scalabilities preserved,the cipherstream can be directly transcoded by some intermediate processing node along the transmission path with no need of the decryption key.The node even doesn't have to be trusted.This is called "encrypt once,decrypt many ways".Compared with other typical encryption schemes,our method features fine granularity of scalability,superior processing speed, excellent bit-error resilience,and negligible file-size overhead.
Then we propose a general key management scheme that is flexible and convenient. All kinds of scalabilities are assorted into two common types,represented by toset and poset,respectively.The entire multimedia content is modeled as the Cartesian product of all tosets and posets,which is a poset itself and can be represented by a Hasse diagram. Access control of the scalable multimedia content is equivalent to access control of the product poset.With the help of a hash-based key derivation method,the decryption key for each vertex can be calculated from the key of its parent vertex and some public auxiliary information.The one-wayness of the hash function ensures key derivation can't be inverted.Users can freely choose and combine the scalability parameters to get a custom version of the original content.For each version a single sub-root key is required to derive all child keys.This is called "protect once,access many ways".
Lastly,we combine the encryption scheme and the key scheme to implement our DRM prototype system on top of Microsoft's WMRM DRM framework.A user only has to pay for what he would like to access.For each access.request from the user, the DRM license server only has to calculate and send a single access key.All keys for child vertices can be derived from the access key and some public auxiliary information. The DRM server doesn't need large storage or powerful processing capability,which in return enhances its reliability and availability.
引文
[1]托马斯·弗里德曼(Thomas L.Friedman),世界是平的(The World Is Flat),湖南科学技术出版社,2006年9月。
[2]Rebert J.McEliece,The Theory of Information and Coding,2nd Edition,Cambridge University Press,Dec.1984.
[3]Thomas M.Cover and Joy A.Thomas,Elements of Information Theory,2nd Edition,John Wiley & Sons,Inc.,2006.
[4]David Salomon,Data Compression—The Complete Reference,4th Edition,Springer-Verlag London Limited,2007.
[5]Weiping Li,"Overview of Fine Granularity Scalability in MPEG-4 Video Standard,"IEEE Trans.on Circuits and Systems for Video Technol.,vol.11,no.3,pp.301-317,March 2001.
[6]"Coding of Audio-Visual Objects,Part-2 Visual,Amendment 4:Streaming Video Profile," ISO/IEC 14496-2/FPDAM4,July 2000.
[7]"Movie piracy cost 6.1 billion," http://torrentfreak.com/movie-piracy-cost-61-billion/.
[8]Fred Piper and Sean Murphy,Cryptography:A Very Short Introduction,Oxford University Press,2002.
[9]William Stallings,Cryptography and Network Security Principles and Practices,4th Edition,Prentice Hall PTR,2005.
[10]B.Schneier,Applied Cryptography:Protocols,Algorithms,and Source Code in C,2nd Edition,John Wiley & Sons,New York,NY,USA,1996.
[11]Alfred J.Menezes,Paul C.van Oorschot and Scott A.Vanstone,Handbook of Applied Cryptograp^y,CRC Press,October 1996.免费版可以从这里获得:http://www.cacr.math.uwaterloo.ca/hac/.
[12]Wenbo Mao,Modern Cryptography:Theory and Practice,Prentice Hall PTR,August,2003.
[13]Whitfield Diffie and Martin Hellman,“New Directions in Cryptography,” IEEE Transactions on Information Theory,vol.IT-22,Nov.1976,pp:644-654.
[14]Ron Rivest,Adi Shamir,and Leonard Adleman,“A Method for Obtaining Digital Signatures and Public-Key Cryptosystems,” Communications of the ACM 21 (2):pp.120-126,1978.
[15]National Bureau of Standards,“Data Encryption Standard,” NBS FIPS Pub.46,January 1977.
[16]William F.Ehrsam,Carl H.W.Meyer,John L.Smith,et al.,“Message Verification and Transmission Error Detection by Block Chaining,” US Patent 4074066,1976.
[17]E.H.McKinney,“Generalized Birthday Problem,”American Mathematical Monthly,vol.73,pp.385-387,1966.
[18]RFC 1321,“The MD5 Message-Digest Algorithm,” http://tools.ietf.org/html/rfc 1321.
[19]FIPS Publication 180,“Secure Hash Standard (SHS),” NIST,May 11,1993.
[20]RFC 2104,“HMAC:Keyed-Hashing for Message Authentication,”http://tools.ietf.org/html/rfc2104.
[21]Stephane Mallat,A Wavelet Tour of Signal Processing,2nd Edition,Academic Press,1999.
[22]Paul S.Addison,The Illustrated Wavelet Transform Handbook,Institute of Physics,2002.
[23]ISO/IEC,“Information Technology—JPEG 2000 Image Coding System,Part 1:Core Coding System,” ISO/TEC 15444-1:2000 (ISO/EEC JTC/SC 29/WG 1 N1646R),March 2000.
[24]Michael W.Marcellin,Michael J.Gormish,Ali Bilgin,et al.,“An Overview of JPEG-2000,” Proc.of IEEE Data Compression Conference,2000.
[25]Charilaos Christopoulos,Athanassios Skodras,and Touradj Ebrahimi,“The JPEG2000 Still Image Coding System:An Overview,” IEEE Transactions on Consumer Electronics,Nov.2000.
[26]ISO/IEC,“JPEG2000 Verification Model 8.5 (Technical Description),” ISO/IEC JTC 1/SC 29AVG 1 N1878,September 2000.
[27]David S.Taubman and Michael Marcellin,JPEG2000 Image Compression:Fundamentals,Standards and Practice,Kluwer Academic,Dordrecht,The Netherlands,2001.
[28]Tinku Acharya and Ping-Sing Tsai,JPEG2000 Standard for Image Compression:Concepts,Algorithms and VLSI Architectures,John Wiley & Sons,New York,NY,USA,2005.
[29]David S.Taubman,“High Performance Scalable Image Compression with EBCOT,” in Proceedings of International Conference on Image Processing (ICIP'99),vol.3,pp.344-348,Kobe,Japan,October 1999.
[30]ISO/IEC,“Information Technology—JPEG 2000 Image Coding System,Part 3:Motion JPEG 2000," ISO/IEC 15444-3:2002.
[31]ISO/TEC,“JPSEC Commission Draft 2.0,”ISO/IEC/JTC 1/SC29/WG 1,N3397,2004.
[32]Frederic Dufaux,Susie Wee,John Apostolopoulos,et al.,“JPSEC for Secure Imaging in JPEG 2000,”in Applications of Digital Image Processing XXVII,vol.5558 of Proceedings of SPIE,pp.319-330,Denver,Colo,USA,August 2004.
[33]Bin B.Zhu,Yang Yang,and Shipeng Li,“JPEG 2000 Encryption Enabling Fine Granularity Scalability without Decryption,” in Proceedings of IEEE International Symposium on Circuits and Systems (ISCAS '05),vol.6,pp.6304-6307,Kobe,Japan,May 2005.
[34]Bin B.Zhu,Yang Yang,and Shipeng Li,“JPEG 2000 Syntax-Compliant Encryption Preserving Full Scalability,” in Proceedings of IEEE International Conference on Image Processing (ICIP '05),vol.3,pp.636-639,Genova,Italy,September 2005.
[35]Bin B.Zhu,Yang Yang,Chang When Chen,et al.,“Fine Granularity Scalability Encryption of MPEG-4 FGS Bitstreams,” in Proceedings of IEEE 7th Workshop on Multimedia Signal Processing (MMSP '05),pp.1-4,Shanghai,China,October2005.
[36]Yang Yang,Bin B.Zhu,Shipeng Li,et al.,“Efficient and Syntax-Compliant JPEG 2000 Encryption Preserving Original Fine Granularity of Scalability,” EURASIP Journal on Information Security,vol.7,Issue 2,Jan.2007.
[37]Philip P.Dang and Paul M.Chau,“Image Encryption for Secure Internet Multimedia Applications,” IEEE Transactions on Consumer Electronics,vol.46,no.3,pp.395-403,2000.
[38]Raphael Grosbois,Pierre Gerbelot,and Touradj Ebrahimi,“Authentication and Access Control in the JPEG 2000 Compressed Domain,”in Applications of Digital Image Processing XXIV,vol.4472 of Proceedings of SPIE,pp.95-104,San Diego,Calif,USA,July 2001.
[39]Susie Wee and John Apostolopoulos,“Secure Scalable Streaming and Secure Transcoding with JPEG-2000,”in Proceedings of IEEE International Conference on Image Processing (ICIP '03),vol.1,pp.205-208,Barcelona,Spain,September 2003.
[40]Hongjun Wu and Di Ma,“Efficient and Secure Encryption Schemes for JPEG2000,”in Proceedings of IEEE International Conference on Acoustics,Speech and Signal Processing (ICASSP '04),vol.5,pp.869-872,Montreal,Quebec,Canada,May 2004.
[41]Yongdong Wu and Robert H.Deng,“Compliant Encryption of JPEG2000 Codestreams,”in Proceedings of the International Conference on Image Processing (ICIP '04),vol.5,pp.3439-3442,Singapore,October 2004.
[42]Osamu Watanabe,Akiko Nakazaki,and Hitoshi Kiya,“A Scalable Encryption Method Allowing Backward Compatibility with JPEG2000 Images,”in Proceedings of IEEE International Symposium on Circuits and Systems (ISCAS '05),vol.6,pp.6324-6327,Kobe,Japan,May 2005.
[43]Jinyong Fang and Jun Sun,“Compliant Encryption Scheme for JPEG 2000 Image Code Streams,”Journal of Electronic Imaging,vol.15,no.4,Article ID 043013,4 pages,2006.
[44]CSE算法的c++语言参考实现(优化和未优化的版本各一),http：／／research．microsoft．comf'binzhu／codes／CSE／．
[45]M.Bellare and R Rogaway,Introduction to Modern Cryptography,Chapter 4,Symmetric Encryption,http:/lwww-cse.ucsd.edul~mihir/cse207/classnotes.html.网页上有笔记和Beamer幻灯片供免费下载。
[46]Min Wu and Yinian Mao,"Communication-Friendly Encryption of Multimedia,"IEEE Workshop on Multimedia Signal Processing,pp.292-295,Dec.,2002.
[47]Hong H.Yu,"Scalable Encryption for Multimedia Content Access Control," IEEE Int.Conf on Acoustics,Speech,and Signal Proc.,vol.2,pp.11-417-420,April 6-10,2003.
[48]JasPer,JPEG 2000标准第I部分的开源C语言实现,作者Michael D.Adams,http://www.ece.uvic.ca/~mdadams/jasper/.
[49]Crypto++,开源的C++语言密码学程序库,维护者是戴伟(Wei Dai),http://sourceforge.net/project/showfiles.php?group_id=6152.
[50]Phillip Rogaway and Don Coppersmith,"SEAL(Software-Optimized Encryption Algorithm)," 1994.U.S.Patent 5454039,"Software-efficient pseudorandom function and the use thereof for encryption," http://pafft.uspto.gov/netacgi/nph-Parser?patentnumber=5454039.
[51]Windows Template Library(WTL),微软发布的开源Windows图形界面程序库,利用C++的模板功能基于微软ATL(Active Template Libary)实现,http://sourceforge.net/project/showfiles.php?group_id=109071.
[52]Bin B.Zhu,Yang Yang,and Shipeng Li,"An Efficient Key Scheme for Multiple Access of JPEG 2000 and Motion JPEG 2000 Enabling Truncations," Consumer Communications and Networking Conference(CCNC),vol.2,pp.1124-1128,2006.
[53]Yang Yang,Bin B.Zhu,and Shipeng Li,"An Efficient Key Scheme for Multiple Access Control of Scalable Multimedia Contents," 尚未发表,2008.
[54]Ryoichi Moil and Masaji Kawahara,"Superdistribution:The Concept and the Architecture,"Transactions of The Institute of Electronics,Information,and Communication Engineers,vol.E73,no.7,pp.1133-1146,Jul.1990.
[55]Ryoichi Mori and Masaji Kawahara,“Superdistribution:An Electronic Infrastructure for the Economy of the Future,”Transactions of the Information Processing Society of Japan,vol.38,no.7,pp.1465-1472,July 1997.
[56]Bin B.Zhu,Chun Yuan,and Shipeng Li,“Scalable Protection for MPEG-4 Fine Granularity Scalability,”IEEE Transactions on Multimedia,vol.7,no.2,pp.222-233,Apr.2005.
[57]Bin B.Zhu,Mitchell D.Swanson,and Shipeng Li,“Encryption and Authentication for Scalable Multimedia:Current State of the Art and Challenges,” Proc.of SPIE Internet Multimedia Management Systems V,Vol.5601,Philadelphia PA,Oct.2004,pp.157-170.
[58]R.C.Merkle,“A Digital Signature Based on a Conventional Encryption Function,” Crypto '87.
[59]Robert H.Deng,Yongdong Wu,and Di Ma,“Securing JPEG2000 Code-Streams,” Int.Workshop Adv.Dev.in Software & Systems Security,Dec.2003.
[60]Cheng Peng,Robert H.Deng,Yongdong Wu,et al.,“A Flexible and Scalable Authentication Scheme for JPEG2000 Image Codestreams,” Proceedings of the eleventh ACM International Conference on Multimedia,pp.433-441,2003.
[61]R.S.Sandhu,“Cryptographic Implementation of a Tree Hierarchy for Access Control,” Information Processing Letters,27(2),pp.95-98,1988.
[62]Leslie Lamport,“Password Authentication with Insecure Communication,” Communications of the ACM 24.11 (November 1981),pp 770-772.
[63]Yongdong Wu,Di Ma,and Robert H.Deng,“Progressive Protection of JPEG2000 Codestreams,”Proc.IEEE International Conference on Image Processing,pp.3447-3450,Singapore,Oct.2004.
[64]Shoko Imaizumi,Osamu Watanabe,Masaaki Fujiyoshi,et al.,“Generalized Hierarchical Encryption of JPEG 2000 Codestreams for Access Control,”IEEE International Conference on Image Processing (ICIP),September 2005.
[65]Bin B.Zhu,Min Feng,and Shipeng Li,“An Efficient Key Scheme for Layered Access Control of MPEG-4 FGS Video,” IEEE International Conference on Multimedia and Expo (ICME)2004,vol.1,pp.443-446,June 2004.
[66]Bin B.Zhu,Shipeng Li,and Min Feng,“A Framework of Scalable Layered Access Control for Multimedia,” IEEE Int.Symp.Circuits and Systems 2005,pp.2703-2706.
[67]Karel Hrbacek and Thomas Jech,Introduction to Set Theory,Third Edition,Revised and Expanded,CRC Press,June 1999.
[68]Eric W.Weisstein,The CRC Concise Encyclopedia of Mathematics,CD-ROM edition 1.0,CRC Press,May 1999.
[69]Sheng Zhong,“A Practical Key Management Scheme for Access Control in a User Hierarchy,” Computer and Security,21(8),2002,750-759.
[70]Keith Frikken,Mikhail Atallah,and Marina Bykova,“Hash-Based Access Control in an Arbitrary Hierarchy,” CERIAS Technical Report 2004-49,Purdue University,Nov.2004.
[71]Bin B.Zhu,Yang Yang,and Tierui Chen,“A DRM System Supporting What You See Is What You Pay,” Digital Rights Management:Technologies,Issues,Challenges and Systems (DRMTICS)2005,LNCS 3919,pp.341-355,2006.
[72]ISO/IEC JTC1/SC29/WG11 13818-11:2003(E),“Information Technology-Generic Coding of Moving Pictures and Associated Audio Information-Part 11:IPMP on MPEG-2 Systems,”2003.
[73]ISO/IEC JTC1/SC29/WG11 14496-13:2004(E),“Information Technology-Coding of Audio-Visual Object-Part 13:Intellectual Property Management and Protection (IPMP)Extensions,”2004.
[74]OMA Digital Rights Management Archive,http://www.openmobilealliance.org/technical/release_program/drm_archive.aspXo当前版本是2008年8月发布的2．1版。
[75]Microsoft Windows Media Digital Rights Management (WMRM),http://www.microsoft.com/windows/windowsmedia/forpros/drm/default.mspx.
[76]Apple Inc.,FairPlay DRM System for QuickTime and iTunes,http://www.apple.com/support/itunes/store/authorization.
[77]IBM,“Electronic Media Management System,” http://www.trl.ibm.com/projects/RightsManagement/datahiding/dhaem_e.htm.
[78]Adobe Digital Editions,http://www.adobe.com/products/digitaleditions.
[79]Sony Corporation,OpenMG DRM scheme,http://www.sony.net/Products/OpenMG/index.html.
[80]RealNetworks,Helix Security Manager,http://www.realnetworks.com/products/drm/index.html.
[81]Windows Media Rights Manager SDK,http://msdn.microsoft.com/enus /windowsmedia/bb190309.aspx.
[82]Microsoft,"Architecture of Windows Media Rights Manager,"http://www.microsoft.com/windows/windowsmedia/howto/articles/drmarchitecture.aspx,May 2004.
[83]Eli Biham and Adi Shamir,"Differential Cryptanalysis of DES-like Cryptosystems,"Advances in Cryptology—CRYPTO '90,Springer-Verlag,2-21,1990.
[84]Kakadu,高质量的JPEG 2000程序库,支持多语言绑定,作者是D.S.Taubman,http://www.kakadusoftware.com.一个早期版本可以从[27]的随书光盘中获得。