Multimedia Security: So What s the Big Deal?

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1 Multimedia Security: So What s the Big Deal? Edward J. Delp Purdue University School of Electrical and Computer Engineering Video and Image Processing Laboratory (VIPER) West Lafayette, Indiana ace@ecn.purdue.edu UT March 21, 2003 Slide 1

2 Multimedia Security Everything is digital these days - a copy of a digital media element is identical to the original How can an owner protect their content? Are images still fossilized light? What does all of this mean in terms of law? What does it mean to own bits? Does any security system really work or does it just make us feel good! UT March 21, 2003 Slide 2

3 What Do We Want From a Security System? Access Control Copy Control Playback Control Record Control Generation Control Auditing (fingerprinting) Who did what and when? UT March 21, 2003 Slide 3

4 What Do Users Want? Time-shifting Format-shifting Single copy (back ups?) If you do not like the owner of the content or disagree with the way it is distributed, should you steal it? UT March 21, 2003 Slide 4

5 Digital Millennium Copyright Act Will it be illegal to remove security features from a data element? Will reverse engineering still be legal? What constitutes distribution? Can I give a data element to my 10,000 closest friends? UT March 21, 2003 Slide 5

6 Digital Communication System UT March 21, 2003 Slide 6

7 Typical Cryptography System: Trusted Users Source Insecure Channel User Attacker Is this a pirate device? UT March 21, 2003 Slide 7

8 Cryptography System: User Not Trusted Source Insecure Channel User Authentication UT March 21, 2003 Slide 8

9 Media Elements Audio Video Documents (including HTML documents) Images Graphics Graphic or Scene Models Programs (executable code) UT March 21, 2003 Slide 9

10 Multimedia Security - Tools Set Encryption Authentication Hashing Time-stamping Watermarking UT March 21, 2003 Slide 10

11 Multimedia Security Applications Privacy Forgery Detection watermarking Copyright Protection watermarking Proof of Purchase (non-deniable) Proof of Delivery (non-deniable) Intruder Detection How do you do this over a noisy wireless channel? UT March 21, 2003 Slide 11

12 What is Watermarking? The use of perceptually invisible authentication techniques controlled distortion is introduced in a multimedia element Visible watermarks also exists UT March 21, 2003 Slide 12

13 Watermarking Scenario Scenario an owner places digital images on a network server and wants to protect the images Goals verify the owner of a digital image detect forgeries of an original image identify illegal copies of the image prevent unauthorized distribution UT March 21, 2003 Slide 13

14 Where are Watermarks Used? Watermarks have been used or proposed in: digital cameras DVD video audio (SDMI dead on arrival) broadcast video (in US - ATSC) visible watermarks now used metadata binding mechanism key distribution systems preventing forgery of bank notes digital cinema analog hole UT March 21, 2003 Slide 14

15 Steganography Steganography - (covered writing) techniques used to hide information within other information to conceal the very existence of the message Used much longer than cryptography Different than crytography in that an illegal user may intercept the message UT March 21, 2003 Slide 15

16 Watermarking The use of perceptually invisible authentication techniques is one form of watermarking distortion is introduced in the data Other forms include visible watermarks UT March 21, 2003 Slide 16

17 A Review of Watermarking Techniques Spatial watermarking Sub-band (wavelet) watermarking DCT coefficient modulation Visible watermarks Watermark Original Image Watermarking Algorithm Watermarked Image UT March 21, 2003 Slide 17

18 Components of a Watermarking Technique The watermark, W each owner has a unique watermark The marking algorithm incorporates the watermark into the image Verification algorithm an authentication procedure (determines the integrity / ownership of the image) UT March 21, 2003 Slide 18

19 Watermark Detection The tradeoff of detectability vs. visibility (host signal interference) Do you need the original image for detection? If not blind detection What about the key? private or public? These are very important when with video UT March 21, 2003 Slide 19

20 Main Principles Transparency - the watermark is not visible in the image under typical viewing conditions Robustness to attacks - the watermark can still be detected after the image has undergone linear and/or nonlinear operations (this may not be a good property - fragile watermarks) Capacity - the technique is capable of allowing multiple watermarks to be inserted into the image with each watermark being independently verifiable UT March 21, 2003 Slide 20

21 Fragile Watermarks Changes to image easily detected and localized Used for authentication, rather than copy detection UT March 21, 2003 Slide 21

22 Attacks Compression Filtering Printing and rescanning Geometric attacks - cropping, resampling, rotation Collusion - spatial and temporal Conversion to analog UT March 21, 2003 Slide 22

23 Spread Spectrum DCT Watermark W is a sequence of random numbers bipolar binary sequence, or N(0,1) X D and Y D are DCT of X and Y a = scaling factor: Y ( i) = X ( i)( 1 + aw ) D D UT March 21, 2003 Slide 23

24 DCT Watermark W * is the extracted version of the watermark Verification: * W S ( W, W ) = W T = user-defined threshold If S > T, image is authentic W * W * * UT March 21, 2003 Slide 24

25 Original Image UT March 21, 2003 Slide 25

26 Fixed-length DCT Watermark a = 0.1 UT March 21, 2003 Slide 26

27 Fixed-length DCT Watermark a = 0.5 UT March 21, 2003 Slide 27

28 Fixed-length DCT Watermark a = 1.0 UT March 21, 2003 Slide 28

29 Fixed-length DCT Watermark a = 5.0 UT March 21, 2003 Slide 29

30 Digital Image Steganography Example cover and stego images produced by S-Tools 4.0 Message: This is a test message demonstrating the S-Tools 4.0 steganography software. Stego key: STEGO Cover Image (8 bits/pixel) Stego Image (8 bits/pixel) UT March 21, 2003 Slide 30

31 Purdue Research Efforts Robust Image-Adaptive Watermarks Fragile and Semi-Fragile Watermarks for Forensic Imaging Robust Video Watermarking Digital Cinema Watermark Evaluation Document Protection and Forensic Analysis Error resilient cryptography Security in Consumer Electronic Devices and Home Networks UT March 21, 2003 Slide 31

32 Image Adaptive Watermarks (DCT) UT March 21, 2003 Slide 32

33 Image Adaptive Watermarks (DCT) UT March 21, 2003 Slide 33

34 Image Adaptive Watermarks (DCT) UT March 21, 2003 Slide 34

35 VW2D Watermarked Image UT March 21, 2003 Slide 35

36 VW2D Difference Image UT March 21, 2003 Slide 36

37 Results - Girls Original Girls Altered Girls fi UT March 21, 2003 Slide 37

38 UT March 21, 2003 Slide 38

39 Watermark Embedding Protocol Embed Input Frame X(t) Watermark W(t) Frame Analyzer Feature Values Watermarked Frame Y(t) Watermark Generator Watermark Key for Next Frame K(t+1) Temporal Redundancy Control Finite State Machine UT March 21, 2003 Slide 39

40 Watermark Detection Protocol Frame Analyzer Test Picture Z(t) Watermark Detector Watermark Generator Watermark State, Key Memory (Queue) UT March 21, 2003 Slide 40

41 Conclusions The secure multimedia system is evolving Simple add-ons will not work (not like the text-based systems) Exploit the unique nature of the type of data Digital watermarking may be crucial to secure networked multimedia systems Time stamping is important New techniques tolerate changes to images, and are compatible with compression UT March 21, 2003 Slide 41

42 Conclusions Watermarking is still an interesting research area with many interesting problems where will it be useful? will watermarking only be used a second-tier security system? will there be significant theoretical developments? Is watermarking the feel good technology of multimedia? UT March 21, 2003 Slide 42

Perceptual Watermarks for Digital Images and Video

Perceptual Watermarks for Digital Images and Video RAYMOND B. WOLFGANG, STUDENT MEMBER, IEEE, CHRISTINE I. PODILCHUK, MEMBER, IEEE, AND EDWARD J. DELP, FELLOW, IEEE Invited Paper The growth of new imaging