Copyright © 2005 UCI ACES Laboratory Kyoungwoo Lee, Nikil Dutt, and Nalini Venkatasubramanian ACES and DSM Donald Bren School of Information and Computer Sciences University of California, An Experimental Study on Energy Consumption of Video Encryption for Mobile Handheld Devices

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #2 Contents 1.Introduction of Video Encryption 2.Video Encryption Algorithms 3.Experiments 4.Conclusion and Issues

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #3 Motivation  Mobile multimedia applications are vulnerable to security attacks in wireless networks  Significant computation for video encryption is expected on battery-operated mobile devices ▶ Evaluate symmetric video encryption schemes from the perspective of energy consumption both analytically and experimentally Problem Introduction

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #4 Secure Video Conferencing Insecure network Attacks Symmetric Encryption Technique Compressed Bit Stream Encrypted & Compressed Bit Stream Raw Video Video Encoder Motion Estimation QuantizationDCT Entropy Encoding Secure Video Encoder Battery -Operated Devices Decompressed Bit Stream Encrypted & Compressed Bit Stream Compressed Bit Stream Video Decoder Entropy Decoding Inverse Quantization IDCT Motion Compensation Secure Video Decoder Battery -Operated Devices Symmetric Decryption Technique

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #5 2. Video Encryption Algorithms 1)Naïve Algorithm 2)Selective Algorithm 3)Zig-Zag Permutation Algorithm 4)Video Encryption Algorithm 5)Sign-Bit Encryption Algorithm 6)Analytical Comparison

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #6 2. Video Encryption Algorithms (0) Symmetric Encryption Technique (DES) Symmetric Encryption Technique  The same encryption technique and the same security key are used to encrypt and decrypt the message (e.g. – DES and AES) A Secret Message A Secret Message #P(&*(UV EncryptDecrypt plaintextciphertextplaintext #P(&*(UV ciphertext network

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #7 2. Video Encryption Algorithms - 1) Naïve Algorithm  Encrypt the entire MPEG stream  Most secure MPEG encryption algorithm because there is no effective algorithm to break DES  Slow  Size of the encrypted stream does not change I-frameP-frame NAÏVE Encryption (DES) I-frameP-frame Video Encoding (H.263)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #8 2. Video Encryption Algorithms - 2) Selective Algorithm  Use the features of MPEG layered structures  Aegis Encryption of I frames Encryption of MPEG video sequence header Encryption of ISO end code  Agi and Gong Great portions of video are visible  partly because of inter-frame correlation  mainly from unencrypted I blocks in the P and B frames In addition, encryption of all I blocks in P and B frames  Encrypting only I frames can save of encryption/decryption time Increase the frequency of I frames  increase the length of string and consequentially the encryption time.  SECMPEG : Meyer & Gadegast A new MPEG-like bitstream  special encoder/decoder required 4 secure level 1)Headers 2)Headers, CD coefficients & lower AC terms of I blocks 3)I frames and I blocks 4)All data  Not safe Encryption of only I frame  visible partly because of inter-frame correlation mainly from unencrypted I blocks in the P and B frames Encryption of headers  (1) mostly standard information such as frame starting code, frame size (2) MPEG stream is indexed by frame

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #9 2. Video Encryption Algorithms - 2) Selective Algorithm (cont’) I-frameP-frame SELECTIVE Encryption (DES) I-frameP-frame Intra-block Video Encoding (H.263)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #10 2. Video Encryption Algorithms - 3) Zig-Zag Permutation Algorithm  Two levels of security to digital image obscured image incomprehensible image  Basic Idea use a random permutation list to map the individual 8x8 block to a 1x64 vector ① Generate a random permutation list ② Split DC coefficient and one of them is saved at the least AC coefficient ③ Apply the permutation list to the split block  Tang (CMU) ① DC coefficient is mapped to the first element in the 1x64 vector and the rest of the elements are permuted.  Obscured image ② DC coefficient of every bock is set to zero or a fixed value between 0 and 255 and rest of the elements are permuted.  Obscured image ③ DC coefficient is mapped to any other position other than the first position in the 1x64 vector, and the rest of the elements are randomly permuted  Incomprehensible image ④ AC63 coefficient is set to 0  Degradation is negligible ⑤ Split the DC coefficient into two parts, first part remain in the same position, the second part is substituted for AC63 and randomly permute the list  Incomprehensible image Vulnerable to the cyphertext attack: Statical analysis(Qiao and Nahrstedt)  binary coin flipping sequence together with two different permutation lists Subject to the plain text attack  Not satisfying security Plaintext attack Cyphertext attack

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #11 2. Video Encryption Algorithms - 3) Zig-Zag Permutation Algorithm (cont’) I-frameP-frame Video Encoding & Zig-Zag Permutation (H.263 & Shuffle)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #12 2. Video Encryption Algorithms - 4) Video Encryption Algorithm  Qiao and Nahrstedt (UIUC) Based on statistical properties of MPEG stream : Uniform distribution of streams faster(47%) than DES because DES is used on partial bit stream Immune to plain-text attack & cypher-text attack  Algorithm 1)Choose odd-numbered bytes and even numbered bytes. 2)XOR the two streams a1,a2… a2n-1 XOR a2,a4… a2n c1,c2… cn 3)Choose an encryption function E (DES ) to encrypt a2,a4… a2n resulting cipher-text has the form c1,c2… cn E(a2,a4… a2n) If a2a4…a2n has no repeated pattern, then the secrecy depends on function E because a2a4…a2n is one-time pad well know to be perfectly secure I-frameP-frame VEA (XOR & DES) I-frameP-frame Video Encoding (H.263)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #13 2. Video Encryption Algorithms - 4) Video Encryption Algorithm (cont’)  All tests on the different MPEG streams show similar statistical results Frequency of Occurrence of Byte Values (The distribution of MPEG stream vs English) Frequency of Occurrence of Byte Values (The distribution of different MPEG streams

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #14 2. Video Encryption Algorithms - 4) Video Encryption Algorithm (cont’)  It is not applicable since byte-values are not uniformly distributed in case of H.263 encoded video stream

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #15 2. Video Encryption Algorithms -5)Sign-Bit Encryption Algorithm  Shi & Bhargava (Purdue)  selective encryption scheme which operates on the sign bits of DCT coefficient of a MPEG compressed video  much more efficient than DES because it selectively encrypts the MPEG stream  Light-weight and cost-effective  Encryption function Ek(S)=…(b1 XOR s1) …(bm XOR sm)(b1 XOR sm+1)…(bm XOR s2m)… Where s1s2…smsm+1…s2m…are all of the sign bits of DC and AC coefficients and the key k=b1b2….bm is a randomly generated bit stream of length m  A more effective modification use a secret key randomly changing the sign bits of differential values of DC coefficients of I frames and the sign bits of differential values of motion vectors very efficient in terms of computational complexity because it omits the encryption of AC coefficients altogether because DC coefficients and AC coefficients are related DC coefficients may be derived from AC coefficients for an attack  Secure Level 1)Encrypting all motion vectors of P frames and B frames 2)Encrypting all DC coefficients of I frames 3)Encrypting all DC coefficients of I frames and all motion vectors of P frames & B frames

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #16 2. Video Encryption Algorithms -5)Sign-Bit Encryption Algorithm (cont’) Blurred but Comprehensible Obscured but Comprehensible incomprehensible

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #17 Comparison of Energy Consumption  Definition of the Size S T size of total encoded bit stream in Byte S I size of I frames in total encoded bit stream in Byte S P size of P frames in total encoded bit stream in Byte S ib_ size of I blocks in S P in Byte S H size of Headers in total encoded bit stream in Byte S T = S I + S P + S H  Definition of amount of Energy Consumption e DES amount of energy consumption to encrypt 1 Byte plaintex using DES(Data Encryption Standard) E algorithm amount of energy consumption to total bit stream using algorithm E encoding amount of energy consumption to encode the video file

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #18 Comparison of Energy Consumption  Naïve Algorithm E Naive = e DES * S T  Selective Algorithm Encryption of I frames  E Sel_I = e DES * S I  E Sel_I = 0.5 * E Naive because S I is b/w 30% & 60% of S T Encryption of I frames and I blocks in P frames  E Sel_I+ib = e DES * ( S I + S ib ) + e overhead  Where e overhead is amount of energy consumption to detect I blocks  E Sel_I+ib = 0.6 * E Naive + α because S ib is b/w 10% & 40% of S I

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #19 Comparison of Energy Consumption (cont’)  Zig-Zag Permutation Basic  E ZZ_basic = 0 * E Naive + α  where α is the energy consumption for split & permutation  However E encoding increases (similar to decrease Quantization value, ex: Q=10  Q=4) Encryption of DC coefficients group  E ZZ_DC = E ZZ_basic + {(# of blocks per frame)*(# of frames in an encoded stream)*e DES } Coin Flipping Sequence  E ZZ_CFS = E ZZ_basic + β  where β is almost zero

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #20 Comparison of Energy Consumption (cont’)  Video Encryption Algorithm E VE = e DES *(½ * S T ) + e XOR ≒ 0.5 * E Naive where e XOR is amount of energy consumption for XOR computation ∵ ½  Sign-Bit Encryption Algorithm E SB = ⅛ * S I * e XOR + δ where e XOR is amount of energy consumption for XOR computation and δ is the energy overhead to extract sign-bits

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #21 Analyzing the Energy Consumption of Security Protocols The larger data size, the more energy consumption

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #22 Comparison of Energy Consumption - example E algorithm E total = E encoding + E algorithm NaiveE Naive = SelectiveE sel_I = E sel_I+ib = Zig-Zag E ZZ_basic ≒ 0 E ZZ_DC = E ZZ_CFS ≒ (when Q = 4) (when Q = 4) Video EncryptionE VE = Sign-Bit EncryptionE SB << < e DES = 2.08 uJ, S T = 233,414 Bytes and E encoding = J in Foreman.263 when resolution = QCIF, Q = 10 & I:P = 1:9

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #23 2. Video Encryption Algorithms - 6) Analytical Comparison AlgorithmSecuritySpeedRelative Energy Consumption Size NaiveVery HighSlow100*No Change SelectiveModerateFast50*/60*Increase Zig-Zag Permutation Very LowVery Fast1*/76*/1*Big Increase Video EncryptionHighFast49*No Change Sign-bit Encryption ModerateFast1*No Change * Analytical Expectation

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #24 3. Experiments 1)Experimental Setup 2)Encoding/Decoding/Encryption 3)Video Encoding by H.263 with Naïve Video Encryption by DES 4)Video Encoding by H.263 with Selective Video Encryption by DES 5)Video Decryption by DES & Video Decoding by H.263

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #25 3. Experiments - 1) Experimental Setup  Experimental Architecture Windows 2000 Advanced Server Desktop PC getpower Linux / Arm 400 MHz Sharp SL-5600 H.263 Coder / DES Crypto National Instruments Power Measurement Device

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #26 3. Experiments - 1) Experimental Setup (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #27 3. Experiments - 1) Experimental Setup (cont’)  Experimental Environments Testbed MachineZaurusstrongARM Encoding AlgorithmH.263 standardPeaCE Encoded FileForeman.QCIF (11,404,800 Bytes) News.QCIF (11,404,800 Bytes) Akiyo.QCIF (11,404,800 Bytes) Foreman.263 (233,414 Bytes) News.263 (162,996 Bytes) Akiyo.263 (81,438 Bytes) Decoded FileEncoded 263 filesNo output file Encryption AlgorithmDESOpenSSL

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #28 3. Experiments - 1) Experimental Setup (cont’)  Experimental Procedure To DoWhere / ToolInputOutput 1Download Input files and Remove wireless NIC PC / FTPFOREMAN.QCIF / H263Encoder / H263Decoder / DESCrypto 2Execute GetPowerPC / Win3270 secondsTotal Energy / Measured Power without Encoder ( = P idle ) 3Execute H263Encoder & GetPower simultaneously Zaurus / terminal & PC / Win32 FOREMAN.QCIF / 70 seconds FOREMAN.263 / Execution Time / Measured Power with encoding ( = P active ) 4Extract PowerWin32 / CalculatorMeasured PowersMeasured Power for Encoding ( = P active -P idle ) 5Compute Measured Total Energy Win32 / CalculatorMeasured Power for Encoding / Total Execution Time Measured Total Energy

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #29 3. Experiments - 1) Experimental Setup (cont’)  Experimental Method Power Time Total Execution Time Average Active Power Average Idle Power Measured Power Active Energy Idle Energy Measured Total Energy

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #30 3. Experiments - 1) Experimental Setup (cont’) Experiments Individual Application (S1) Video Encoder (H.263) -FOREMAN.qcif w/ 300 frames of 11MB -1:10 (IP ratio), 10 (Quant), Full Search (S2) Video Decoder (H.263) -Variable encoded bit streams -233 KB with default (S3) Crypto Application (DES) -233 KB of encoded bit stream Integrated Application (I1) Encoder with Full Encryption -Integrate (S1) and (S3) -Variable Quant & fixed others (I2) Encoder with Partial Encryption -Integrate (S1) and (S3) to encrypt only Intra-blocks with the same parameters (I3) Decoder with Full Decryption - Integrate (S2) and (S3)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #31 3. Experiments - 1) Experimental Setup (cont’)  Definitions Total Execution Time (second): total time to execute encoding, decoding or encryption on Zaurus Measured Total Energy (Joule): Total Execution Time * Measured Power[= P active -P idle ] Energy Consumption per byte (uJoule): Measured Total Energy / size of input file Energy Consumption per second (Watt): Power = Measured Total Energy / Total Execution Time = Measured Power Ratio(%): Encryption Energy Overhead = 100 * (Energy Consumption for Encoding with Encryption / Energy Consumption for Encoding)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #32 3. Experiments - 2) Encoding/Decoding/Encrypt H.263 Encoding H.263 Decoding DES Encryption [Decryption] Total Execution Time (seconds) Measured Total Energy (Joule) Energy Consumption per Byte (uJoule) Measured Power (Watt) Input file: FOREMAN.qcif (11,404,800 bytes) Encoder parameters: Q=10, IP ratio=1:10 and default parameters

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #33 3. Experiments - 3) Video Encoding & Encrypt Encoding w/o Encryption Encoding w/ Encryption Ratio (%) Total Execution Time (second) Measured Total Energy (Joule) Measured Power (Watt)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #34 3. Experiments - 3) Video Encoding & Encrypt (cont’) Application Measured Energy (Joules) H.263 EncoderH.263 DecoderDES Crypto Huge Difference (98 %)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #35 3. Experiments - 3) Video Encoding & Encrypt (cont’) FOREMAN.qcifNEWS.qcif Video Clips Measured Energy (Joules) Encoding without Encryption Encoding with Encryption (Selective) Encoding with Encryption (Naïve) (2.4%) (1.7%) Negligible Energy Overhead

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #36 3. Experiments - 3) Video Encoding & Encrypt (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #37 3. Experiments - 4) Naïve & Selective Encryption FOREMAN.qcifEncoding w/o Encryption Encoding w/ Naïve Encryption Encoding w/ Selective Encryption Total Execution Time (second) Measured Total Energy (Joule) Energy Difference from Encoding Encrypted File Size (Byte) -233,40820,536

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #38 3. Experiments - 4) Naïve & Selective Encryption (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #39 3. Experiments - 5) Video Decrypt & Decoding Decoding w/o Decryption and Decoding Ratio (%) Total Execution Time (seconds) Measured Total Energy (Joule)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #40 3. Experiments - 6) Quality and Security Level

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #41 3. Experiments - 6) Quality and Security Level (cont’) LevelQualityQuantizationSecurityEncryption 1HighQ=1HighNaïve 2LowNo/Sel 3Mid-HighQ=4HighNaïve 4LowNo/Sel 5Mid-LowQ=10HighNaïve 6LowNo/Sel 7LowQ=31HighNaïve 8LowNo/Sel

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #42 3. Experiments - 6) Quality and Security Level (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #43 3. Experiments - 6) Quality and Security Level (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #44 3. Experiments - 6) Quality and Security Level (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #45 3. Experiments - 6) Quality and Security Level (cont’)  Other Parameters to effect on QnS Level Resolutions Decoding Side Number of Users Others

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #46 4. Conclusion and Issues 1)Conclusion 2)Issues 3)Next Step

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #47 4. Conclusion and Issues - 1) Conclusion ① Energy Consumption for Video Encryption is not a big deal comparing to that for Video Encoding ② Energy Consumption for Video Decryption is critical ③ Energy for Video Encryption/Decryption increases with an increase of the encoded file size ④ Selective Algorithm is more energy-efficient but less secure than Naïve Algorithm

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #48 4. Conclusion and Issues - 1) Conclusion (cont’) ⑤ High quality Encoding (eg: quantization) [  low compression)  Increase energy consumption for encryption ( ∵ usually high quality video encoding increases the file size)  Increase energy consumption for decoding ⑥ IP ratio (Naïve Video Encryption vs Selective)  Decrease IP ratio in Encoding (assumption: only encrypting I-frames)  Possible to decrease energy consumption  But we have to consider increase of energy in encoding & decoding and compare it with decrease of energy in encryption & decryption)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #49 4. Conclusion and Issues - 2) Issues ② Ideas I.Hybrid Video Encryption Algorithms  Main Idea: Encrypt I-frames and I-blocks in P-frames by Video Encryption Algorithm  We can reduce computation to half of Selective Algorithm  Assumption: Byte values in I-frames and I-blocks are even distributed

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #50 4. Conclusion and Issues - 2) Issues (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #51 4. Conclusion and Issues - 2) Issues (cont’)

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #52 4. Conclusion and Issues - 2) Issues (cont’) ② Ideas (cont’) II.Key Chain using One-Way Hash function  Main Idea: Encrypt each block data using XOR with a Key Value generated by One-way Hash function.  One-Way Hash function such as MD-5 and SHA-1 is very hard to crash and very fast and XOR is absolutely fast as well.

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #53 H.263 Encoder Uncompressed Video Encoded Bitstream H.263 Decoder Decoded Video Decrypted Encoded Bitstream DES Encryption Encrypted Bitstream Encrypted Bitstream DES Decryption Hashed Key Chain One-Time Pad

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #54 Internet access point Mobile Device access point Mobile Device Proxy router Proxy creates hash key chain for one session unit 2 Proxy downloads(offline) hash key chain to Mobile Device 3 Mobile Device encrypts video data by XOR operation of video block with key block 1 2 3

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #55 4. Conclusion and Issues - 2) Issues (cont’) ② Ideas (cont’) II.Key Chain using One-Way Hash function H 1 = h(K) H 2 = h(H 1 ) … H i = h(H i-1 ) … B 1 B 2 B 3 … B i … XORH 1 H 2 H 3 … H i … C 1 C 2 C 3 … C i … Generate Key Values starting from a seed Key, K which is shared securely

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #56 4. Conclusion and Issues - 2) Issues (cont’) ② Ideas (cont’) II.Key Chain using One-Way Hash function 1.Can I make a key chain using SHA-1 with one seed key? (one seed key is less than 2 64 bits and then 160 bits) 2.SHA-1 is one-way hash function. How secure is SHA-1? 3.Which one is more secure, sequential key chain or reverse key chain? 4.Offline download from TTP server to MD is good in terms of security? 5.How about making key chain using AES? (reference shows that AES is more energy efficient than SHA-1) 6.Overall this method, One-time pad with hashed key chain, seems secure? Questions

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #57 4. Conclusion and Issues - 2) Issues (cont’) ② Ideas (cont’) II.Spatially Partial Encryption of frame

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #58 4. Conclusion and Issues - 3) Next Step  Experiment H.263 Video Decoding with DES Decryption  Devise idea to guarantee video security and to decrease energy consumption  Analyze and simulate energy consumption for encryption/decryption in multi-user video conferencing/video streaming/ broadcasting  ???

Copyright © 2005 UCI ACES Laboratory ICME 2005 July 7 th #59 References 1)A Fast MPEG Video Encryption Algorithm : 2)Critical Analysis of MPEG Encryption Schemes : 3) 4)T.B Maples and G.A.Spanos. Performance Study of a Selective Encryption Scheme for the Security of Networked Real-time Video. In Proceedings of 4th International Conference on Computer Communications and Networks, Las Vegas, Nevada, September )L.Agi and L.Gong. An Emprical Study of MPEG Video Transmissions. In Proceedings of the Internet Society Symposium on Network and Distributed System Security, pages , San Diego, CA, Feb )L.Tang Method for Encrypting and Decrypting MPEG Video Data Efficiently. In Proceedings of the Fourth ACM International Multimedia Conference (ACM Multimedia ’96), pages , Bosten, MA, November )Qiao and Nahrstedt Comparison of MPEG Encryption Algorithms. International Journal of Computers and Graphics, special issue: “Data Security in Image Communication and Network” vol.22 January )Shi and Bhargava An Efficient MPEG Video Encryption Algorithm. Proceedings of the IEEE Symposium on Reliable Distributed Systems 1998, IEEE Comp. Soc. Los Almitos, CA, USA 98CB36281 P )Nachiketh R. Potlapally, Srivaths Ravi, Anand Raghunathan and Niraj K. Jha, “Analyzing the Energy Consumption of Security Protocols”