Copy Protection for DVD Video

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

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

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

4. Encrypted content Key exchange between compliant devices only IEEE 1394 cable Agenda II - DVD Copy Protection system in1999 III - Content Protection During Digital Transmission IV - Watermark System Design Issues Watermark: Copy once Copy never … DVD recorder copy1 V - Copy-Generation Management copy2 copy1

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. header 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) MPEG stream Not NTSC/PAL encoded encoder 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 CCI Copy_freely Copy_never Copy_once header MPEG stream

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. Encrypted content Key exchange between compliant devices only IEEE 1394 cable II - DVD Copy Protection system in 1999 • 3 additional components being considered: • Protection Transmission system • Media identifiers • Watermarking 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 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 Copy_freely Copy_never Copy_once header MPEG stream - 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 Watermarking With Watermarking DVD RAM without CSS or CGMS No keys Strip out CCI: copy control bits Cannot remove the CCI: watermark Analog RGB to appropriate non compliant recorder 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 Drive Within 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: Dual system -> sol: compliant drive & compliant application program Cons: Additional complexity

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 Record video “Copy-no-more” “Copy-once” 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

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