Copy Protection for DVD Video

J.Bloom, I.Cox,T.Kalker,J.P.Linnartz,M.Miller, and C.B.S.Traw

1999 Aline Martin [email protected]

ECE 738 Project – Spring 2005

I - Introduction

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

I - Introduction

• Encryption not enough: Decrypted content

Back of DVD player

Additional protections needed

Agenda

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

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”

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) 2 keys only read by compliant drives Lead in Lead out Prevent byte-for-byte copies of an MPEG stream from being playable since copy does not include keys

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) header MPEG stream Not NTSC/PAL encoded encoder VCR

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 MPEG stream header CCI Copy_freely Copy_never Copy_once

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

II - DVD Copy Protection system in

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

II - DVD Copy Protection system in

1999 • 3 additional components being considered: – Protection Transmission system – Media identifiers – Watermarking Watermarking: Do not survive D/A conversion Watermark encoding the same info: - Survive D/A conversion Record control Copy_freely - Not too easily strip out header Copy_never MPEG stream Copy_once - Reduces the value of illegal, unencrypted copies by making them unplayable on compliant devices: Playback control

No keys

II - DVD Copy Protection system in

1999 Without Watermarking With Watermarking DVD RAM without CSS or CGMS Strip out CCI: copy control bits Analog RGB to appropriate non compliant recorder Cannot remove the CCI: watermark IEEE 1394 standard Most devices will be compliant

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

III - Content Protection During Digital Transmission

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

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 Cons: Additional complexity Pros: MPEG Codec and detector can share a lot of resources.

Cons: Dual system -> sol: compliant drive & compliant application program

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

V – Copy-Generation Management Record video “Copy-once” “Copy-no-more” 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

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 2 nd undetectable watermark

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’

Questions?