1. Copy Protection for DVD Video Aline Martin alinemartin@wisc.edu ECE 738 Project – Spring 2005 J.Bloom, I.Cox,T.Kalker,J.P.Linnartz,M.Miller, and C.B.S.Traw 1999

2. I - Introduction 1996: First DVD players ProsCons High quality videocopy perfect reproduction vs VHS Late 1999: DVD recorders Copy Protection Movie-> MPEG-2 & encryption->DVD

3. I - Introduction Encryption not enough: Back of DVD player Decrypted content Additional protections needed

4. Agenda II - DVD Copy Protection system in 1999 III - Content Protection During Digital Transmission IV - Watermark System Design Issues V - Copy-Generation Management IEEE 1394 cable Encrypted content Key exchange between compliant devices only Watermark: Copy once Copy never … copy1 DVD recorder copy1 copy2

5. II - DVD Copy Protection system in 1999 1996: CPTWG (Copy Protection Technical Working Group) –Discuss technical pbs of protecting digital video piracy –No official decision-making power –1998-1999: design major part of copy protection system 2 major principles guided the CPTWG’s work: - Copy-protection system not mandatory - Copy-protection system cost effective “Keep honest people honest”

6. II - DVD Copy Protection system in 1999 3 components built: –CSS: Content Scrambling System –APS: Analog Protection System –CGMS: Copy Generation System CSS: Low cost method of scrambling MPEG-2 video (Matsushita) Lead in Lead out 2 keys read by compliant drives only Prevent byte-for-byte copies of an MPEG stream from being playable since copy does not include keys

7. II - DVD Copy Protection system in 1999 3 components built: –CSS: Content Scrambling System –APS: Analog Protection System –CGMS: Copy Generation System APS: Encodes NTSC/PAL signals so cannot be recorder on VCR but play on TV (Macrovision) encoder Not NTSC/PAL encoded header MPEG stream VCR

8. II - DVD Copy Protection system in 1999 3 components built: –CSS: Content Scrambling System –APS: Analog Protection System –CGMS: Copy Generation System CGMS: Pair of bits in header MPEG stream header MPEG stream Copy_freely Copy_never Copy_once CCI

9. II - DVD Copy Protection system in 1999 3 components built: –CSS: Content Scrambling System –APS: Analog Protection System –CGMS: Copy Generation System 3 additional components being considered: –Protection Transmission system –Media identifiers –Watermarking

10. II - DVD Copy Protection system in 1999 3 additional components being considered: –Protection Transmission system –Media identifiers –Watermarking IEEE 1394 cable Encrypted content Key exchange between compliant devices only Protection Transmission system:

11. II - DVD Copy Protection system in 1999 3 additional components being considered: –Protection Transmission system –Media identifiers –Watermarking Media identifier: - Identify recordable media - Identify whether a compliant recorder has produced the disk - Distinguish between original ROM disks and a piracy copy

12. II - DVD Copy Protection system in 1999 3 additional components being considered: –Protection Transmission system –Media identifiers –Watermarking Watermarking: - For a more secure form than CGMS: Record control header MPEG stream Copy_freely Copy_never Copy_once Do not survive D/A conversion Non compliant player strip out copy-control bits Watermark encoding the same info: - Survive D/A conversion - Not too easily strip out - Reduces the value of illegal, unencrypted copies by making them unplayable on compliant devices: Playback control

13. II - DVD Copy Protection system in 1999 Without WatermarkingWith Watermarking No keys Strip out CCI: copy control bits DVD RAM without CSS or CGMS Analog RGB to appropriate non compliant recorder Cannot remove the CCI: watermark IEEE 1394 standard Most devices will be compliant

14. III - Content Protection During Digital Transmission transmission DTDG (Digital Transmission Discussion Group) decided: - Content: encrypted - Exchange of CCI: robust - AKE: Authentication for compliant devices Key exchange: keys to exchange encrypted content

15. III - Content Protection During Digital Transmission

16. IV – Watermark System Design Issues Economic Costs: - Watermark detector must fit onto unused silicon already in the drive False Positives Rate: - Detector should be good at deciding whether a watermark is present Interaction with MPEG compression: - Watermark adds details that MPEG encoder tries to preserve -> reduce bits available for content  minimize this effect - Watermark detectable in both compressed data stream and reconstructed video

17. IV – Watermark System Design Issues Detector Placement: In the DriveWithin the Application Pros: Pirated content will never leave the drive and or will never copied onto a disk Pros: MPEG Codec and detector can share a lot of resources. Cons: Additional complexity Cons: Dual system -> sol: compliant drive & compliant application program

18. IV – Watermark System Design Issues Robustness: Common signal processing: - Geometric distortion - Scaling - Cropping Intentional Tampering: Watermark more difficult to find

19. V – Copy-Generation Management Copy-generation management requires that the “copy-once” state be detected and changed to a “copy-no-more” state as the video is being recorded. 2 Approaches: - Secondary watermark - Removal of additional information: Tickets “Copy-once” “Copy-no-more” Record video

20. V – Copy-Generation Management Secondary Watermark: Watermark #1 for “Copy-once”Watermark #1 + Watermark #2 for “Copy-no-more” Record video Computationally inexpensive Insertion in both baseband and compressed video domain Robust Unobtrusive More susceptible to tampering => Want to make the 2 nd watermark undetectable

21. V – Copy-Generation Management Tickets: Solution to tampering T: cryptographic counter implemented as a multi-bit random number contents # n of playbacks & recording generations allowed T T’

22. Questions?