1. Adaptive VoIP Steganography for Information Hiding within Network Audio Streams 1 2011 International Conference on Network-Based Information Systems Author(s): Erchi Xu, Bo Liu, Liyang Xu, Ziling Wei, Baokang Zhao ∗, Jinshu Su

2. Outline Introduction VAMI VADDI Experimental Results Conclusion Reference 2

3. Introduction VoIP information Embedding Process. 3

4. Introduction(cont.) G.711 codec 4

5. Introduction(cont.) Common hiding process LSB(Least Significant Bits) 5

6. Introduction(cont.) MOS(Mean Opinion Score). Required 16 experts to obtain MOS. 6

7. VAMI VAMI(VAlue-based Multiple Insertion) According to PCMU, notation bits are the same. LSB data hiding method is easy to detect. Creating multiple data hiding way by different modes. 7

8. VAMI(cont.) 8 Pesq(n,t) = MOS nt

9. VAMI(cont.) The process of VAMI. Only use mode 0~3. 9

10. VADDI VADDI(Voice Activity Detection Dynamic Insertion) Hiding data in the silent part is easy to be find out. Define a threshold L, if higher than L start hiding, otherwise, stop. 10

11. VADDI(cont.) 11 Define a threshold L, if higher than L start hiding, otherwise, stop.

12. Experimental Results 12

13. Experimental Results(cont.) 13

14. Conclusion Nowadays, existing VoIP steganography research commonly focus on information hiding in the LSB bits of Network Audio Streams. Existing detection way NVR is targeting on LSB method, so LSB method is not a efficient way for VoIP steganography. Using AVIS method will be more suitable than LSB method. 14

15. Reference [1] N. Provos and P. Honeyman, “Hide and seek: An introduction to steganography,” IEEE Security and Privacy, vol. 1, pp. 32–44, May 2003. [2] C. Wang and Q. Wu, “Information hiding in real-time voip streams,” in Proceedings of the Ninth IEEE International Symposium on Multimedia, ser. ISM ’07. Washington, DC,USA: IEEE Computer Society, 2007, pp. 255–262. [3] C. Wang, “improved voip security with real-time speech hiding in g.711,” Ph.D. dissertation, National Chi Nan University,2007. 15