June 2007

1. An Experimental Study on Energy Consumption of Video Encryption for Mobile Handheld Devices Insecure network V Zaurus Overview of Secure Video Applications Attacks Problem and Motivation Battery -Operated Devices Battery -Operated Devices V Video Encoder Video Decoder R • Mobile multimedia applications are vulnerable to security attacks in wireless networks • Significant computation for video encryption is expected onbattery-operated mobile devices Motion Estimation DCT Quantization Entropy Encoding Entropy Decoding Inverse Quantization IDCT Motion Compensation Raw Video Compressed Bit Stream Compressed Bit Stream Decompressed Bit Stream Symmetric Encryption Technique Symmetric Decryption Technique • Evaluate symmetric video encryption schemes from the perspective of energy consumption both analytically and experimentally Secure Video Encoder Secure Video Decoder Encrypted & Compressed Bit Stream Encrypted & Compressed Bit Stream Analytical Study of Video Encryption Schemes with respect to Energy Consumption Studied Video Encryption Schemes Analytical Comparison of Video Encryption Schemes (1) Naive Encryption Scheme (2) Selective Encryption Scheme Algorithm Security Speed Size Drawback Relative Energy Video Encoding (H.263) Selective Encryption (DES) P-frame P-frame I-frame P-frame P-frame I-frame Naive Encryption of all frames High Slow No Change Significant Computation 100 % • EnergyNaive=eDES*STotal Intra-block Video Encoding (H.263) Naive Encryption (DES) • EnergySelective = eDES*SIB • eDES - energy to encrypt one byte by DES • STotal - size of the whole video data Selective Partial encryption (e.g. Intra-blocks) Moderate Fast No Change Moderate Security 59 % • SIBl - size of Intra-blocks in video data P-frame P-frame I-frame P-frame P-frame I-frame (4) Video Encryption Algorithm (VEA) (3) Zig-Zag Permutation Scheme Zig-Zag Shuffling coefficients from Quantization Very Low Very Fast Big Increase Breaks efficiency of Video Encoding < 1 % Video Encoding & Zig-Zag Permutation (H.263&Shuffle) VEA (XOR &DES) Video Encoding (H.263) P-frame P-frame I-frame P-frame P-frame I-frame P-frame P-frame I-frame VEA XORing and Half Encryption using even byte distribution High Fast No Change Not applicable for H.263 without even distribution 50 % • EnergyZig-Zag = eoverhead • EnergyVEA = ½*(eDES+eXOR)*STotal • eoverhead - energy to shuffle coefficients • eXOR - energy for XOR • Naïve encryption scheme consumes twice the energy of Selective encryption scheme Experimental Study on Tradeoffs between Security and Energy Consumption Experimental Setup System Architecture Energy Consumption for Varying Quality & Security Experimental Results Secure Video Application (Encoder / Decoder) Negligible Energy Overhead Quality (Quant Scale) Security (Full vs. Partial) Measured Energy (J) Energy Overhead 80 74.77 90 77.62 70 75.78 74.77 80 74.11 72.87 72.26 High (Quant = 1) High (Full) 128.2 13 % 60 70 Huge Difference (98%) (2.4%) (1.7%) DES H.263 Codec Device Driver 60 50 Low (Partial) 111.0 Measured Energy (Joules) Encoding without Encryption 50 5 V Measured Energy (Joules) 40 OpenSSL Library Mid-High (Quant = 4) High (Full) 92.05 9 % Encoding with Encryption (Selective) 40 30 Encoding with Encryption (Naïve) Low (Partial) 83.56 30 20 Operating System (Linux) R = 22 ohm 11.37 20 Mid-Low (Quant = 10) High (Full) 77.62 2 % 10 Appropriate for mobile video 1.5 10 Low (Partial) 75.78 0 0 Application Mobile Handheld Hardware (Sharp Zaurus) FOREMAN.qcif NEWS.qcif Low (Quant = 31) High (Full) 70.44 1 % H.263 Encoder H.263 Decoder DES Crypto Video Clips • 11 MB with 300 frames • 1:10(IP ratio),10(Quant),full search • DAQ board with BNC Connector • Windows XP • 1,000 samples/sec Low (Partial) 69.89 • Encryption consumes negligible energy as compared to encoding • Energy consumption of encryption is negligible irrespective of video clips • 400 MHz Intel XScale • 64 MB flash & 32 MB SDRAM VR • Energy overhead for full video encryption is NEGLIGIBLE PZaurus = * VZaurus Power Measurement System R Donald Bren School of Information and Computer Sciences University of California, Irvine, CA 92697 {kyoungwl, dutt, nalini}@ics.uci.edu For more details : http://forge.ics.uci.edu/ Kyoungwoo Lee, Nikil Dutt, Nalini Venkatasubramanian June 2007