1. Real-Time Watermarking Techniques for Sensor Networks 4th, December Tae woo Oh Jessica Feng, Miodrag Potkonjak Dept. of Computer Science Univ. of California 2003 SPIE

2. Contents 1. Introduction 3. Example 4. Watermark generation 2. Proposed method 6. Conclusion 2/17 5. Experimental Result

3. Introduction [1/2]  IPP(Intellectual Property protection) in WSN 3/17 WSN has emerged as the major criteria. WSN(Wireless Sensor Network) processes a great deal of information. WSN is more susceptible to attacks. → Urgent need for development of IPP techniques Solution : Watermarking Technique !

4. Introduction [2/2]  Watermarking Process of embedding hidden data into an object - Hidden data = Watermark = Cryptologically encoded authorship Application - Ownership assertion - Copy prevention or control - Fraud and tamper detection Two groups ① Static domain WM - Using imperfection of the human perceptive system → Video, Audio ② Functional domain WM - Using the fact that there are many solutions of similar quality → Software, WSN 4/17

5. Proposed Method [1/3]  Watermarking in WSN Embedding watermarks into data and information acquired by wireless embedded sensor networks. Key idea - Imposing additional constraints during the data acquisition or sensor data processing → Constraint = Watermark → It is possible to add constraints, because data acquired by sensor have some errors. - Deciding constraints → Balance between strength of watermark and quality of data 5/17

6. Proposed Method [2/3]  Watermarking in WSN 6/17 + Constraints(watermark) Solution range before watermarking Solution range after watermarking

7. Proposed Method [3/3] 7/17 Formulate equations to represent relationships in a particular network Formulate equations to represent relationships in a particular network Rewrite equations in terms of measured values and errors Rewrite equations in terms of measured values and errors Rewrite equations according to non-linear programming format : in terms of an objective and constrains Add/alter constrains or objective functions to embed watermark Solve the equations by using existing non- linear integer programming solver → Watermarked solution  Generic procedure for embedding a WM STEP 1 STEP 2 STEP 3 STEP 4 STEP 5

8. Obtained data - (x A,y A ), (x B,y B ), (x C,y C ), d XA, d XC, d XB Unknwon data - (x X,y X ) Example [1/6]  Embedding WM during Trilateration process 8/17 → Determining the coordinates of a node X from data obtained by node A,B,C

9. Example [2/6]  Embedding WM during Trilateration process 9/17 STEP1 : Equation to represent relationships of nodes → From above equation We can get solution (x X,y X ). But, because of noises of measured data, this problem is changed to non-linear problem, minimizing the error of solution. STEP2 : Need to consider several errors → The errors in measurement of. are the errors between Euclidean distance and measured distance.

10. Example [3/6]  Embedding WM during Trilateration process 10/17 STEP3 : Objective function and Constraints ▶ Objective function ▶ Constraints

11. Example [4/6]  Embedding WM during Trilateration process 11/17 STEP4 : Adding Watermarking Constraints ▶ Watermark ▶ Assignment of numbers to the variables of the objective function ▶ Divide watermark according to above table number

12. Example [5/6]  Embedding WM during Trilateration process 12/17 STEP4 : Adding Watermarking Constraints ▶ Add new constraints according to watermark patterns 1101000 0011101 1010010 010 → Adding new constraints c 4, c 5, c 6, c 7. v1, v2, v3, v4 are threshold.

13. Example [6/6]  Embedding WM during Trilateration process 13/17 STEP5 : Solving the equation by using solvers ▶ Taking objective function and all constraints into account ▶ The solution is watermarked solution ▶ Using non-linear programming solvers Equation Objective FN Constraints Added Constraints Watermarked solution Watermarked solution Equation Objective FN Constraints Added Constraints Watermarked solution Watermarked solution Checking validation of watermark Watermarked solution Watermarked solution Apply Sender node XReceiver node

14. Watermark Generation  Watermark generation scheme 14/17 Textfile MD5 Hash RSA Seedfile RC4 Watermark Private Key Private Key PGP Software Package

15. Experimental Result 15/17  Trilateration Watermark Test

16. Conclusion  Conclusion IPP technique in Wireless Sensor Network Using Watermark ▶ Data obtained by sensor have some error. ▶ Watermarked solution ≒ Original solution Problem ▶ Time overhead problem ▶ Decision of constraints ▶ For accurate solution, need to many overhead ! 16/17

17. Q & A  Q & A 17/17