1. Problem and Motivation
Mobile multimedia application is vulnerable to
malicious attacks in wireless communication
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
Overview of Secure Video Applications
network
Symmetric
Encryption
Compressed
Bit Stream
Encrypted &
Raw
Video
Video Encoder
Shuffling
Coefficients
Naive
Selective
VEA
Zig-Zag
Motion
Estimation
Quantization
DCT
Entropy
Encoding
Secure Video Encoder
Decryption
Decompressed
Video Decoder
Unshuffling
Decoding
Inverse
IDCT
Compensation
Secure Video Decoder
Malicious
Attacks
Battery
-Operated
Devices
This is an study of video encryption for mobile handheld devices in terms of energy consumption.
Emerging mobile multimedia applications such as military video conferencing and video surveillance is subject to malicious attacks during transmission, especially in wireless communication. And we expect video encryption consumes pretty high energy because of the significant computation for symmetric encryption techniques. So we evaluate several video encryption techniques in terms of energy consumption for mobile devices by analysis and experiments as well.
They are typical steps of video application and in order to make it secure, they encrypt video data right after entropy encoding and decrypt it before general steps of video decoding.
At first we evaluate the previous video encryption schemes analytically in terms of energy consumption. Naïve encryption scheme encrypts the whole video data with symmetric encryption technique such as DES and AES. It is highly secure but slow compared to selective encryption scheme. Selective encryption scheme encrypts partial data of video like intra-frames or intra-blocks. It’s less secure than Naïve algorithm but faster. On the other hand, Zig-Zag permutation algorithm shuffles coefficients before entropy encoding. However it’s not secure and it breaks the efficiency of video encoding. The basic idea of VEA is to use the uniform distribution of byte values so they encrypts the half of the stream after xoring two halves. But when I looked at the distribution of byte value in h.263 encoded video data, which are not distributed uniformly. So we don’t consider the last two encryption schemes and analysis shows the relative energy consumption of each video encryption scheme and full encryption, in other words naïve video encryption scheme, may consume energy as twice as partial encryption according to the portion of intra-blocks.
To measure the power consumption, we implement the real video encoder and decoder with full encryption technique and partial encryption and set up the experiments as shown in this picture using sharp zaurus PDA. And we define the level of quality and security based on video quality dominated by quantization scale and degree of security using full encryption or partial encryption. As we expect, higher quality and security video encoder consumes higher energy. However the energy overhead for full video encryption is not a big deal, which shows just 2 % energy overhead when we look at the level 5 and 6, which are appropriate for mobile application. Other experimental shows that energy consumption for video encryption is negligible compared to video encoding and energy consumption of encryption is very small irrespective of video clips.
Any questions?
Analytical Study of Video Encryption Schemes with respect to Energy Consumption
Studied Video Encryption Schemes
Analytical Comparison of Video Encryption Schemes
(1) Naïve Encryption Scheme
Treats video data like a text stream with
symmetric encryption technique (e.g. DES)
Highly secure but slow
No change in size after encryption
Encrypts the partial video (e.g. Intra-blocks)
Med. secure but faster than full NAÏVE
No change in size after encryption
(2) Selective Encryption Scheme
Shuffles the coefficients
Insecure but very fast
Breaks the efficiency of encoding
(3) Zig-Zag Permutation Scheme
Encrypts half of the stream after XORing
Secure and comparably fast
But byte values of data are not uniformly
distributed in case of H.263
(4) Video Encryption Algorithm (VEA)
Algorithm
Relative
Energy
Naive
100 %
Selective
59 %
I-frame
P-frame
Video Encoding
& Zig-Zag
Permutation
(H.263 & Shuffle)
Video
Encoding
(H.263)
VEA
(XOR & DES)
Intra-block
I-frame
P-frame
Selective
Encryption
(DES)
Video
Encoding
(H.263)
I-frame
P-frame
Naive
Encryption
(DES)
Video
Encoding
(H.263)
P-frame
P-frame
I-frame
P-frame
P-frame
I-frame
Zig-Zag
< 1 %
VEA
50 %
EnergyZig-Zag = eoverhead
eoverhead - energy to shuffle coefficients
EnergyVEA = ½*(eDES+eXOR)*STotal
eXOR - energy for XOR
EnergyNaive=eDES*STotal
EnergySelective = eDES*SIB
eDES - energy to encrypt one byte by DES
STotal - size of the whole video data
Full Encryption (Naïve) may consume energy as twice as Partial (Selective) Encryption
SIBl - size of Intra-blocks in video data
Experimental Study on tradeoffs between Quality with Security and Energy Consumption
Experimental Setup
Measured Energy Consumption of Quality & Security Videos
Energy overhead for full video encryption is NEGLIGIBLE
Quality &
Security
Quality
(Quant Scale)
(Full vs. Partial) 1 2 3 4 5 6 7 8
High
(Quant = 1)
Mid-High
(Quant = 4)
Mid-Low
(Quant = 10)
Low
(Quant = 31)
High (Full)
Low (Partial)
Measured
Energy (J)
Energy
Overhead
128.2
111.0
92.05
83.56
77.62
75.78
70.44
69.89
13 %
9 %
2 %
1 %
Higher Quality of Video
High Degree of Security
Experimental Results
Negligible Energy Overhead
PZaurus = * VZaurus VR R 80
74.77 90
77.62 70 80
74.77
75.78
74.11
72.26
72.87 60
Huge
Difference
(98%) 70
(2.4%)
(1.7%)
System Architecture 50 60
Secure Video
Application
(Encoder / Decoder)
Measured Energy (Joules) 50
Encoding without Encryption 40
Measured Energy (Joules)
5 V V
Zaurus
Encoding with Encryption (Selective) 40
DES
H.263
Codec
Device
Driver 30
Encoding with Encryption (Naïve) 30
OpenSSL
Library 20
R = 22 ohm
11.37 20
Operating System
(LINUX) 10
1.5 10
Mobile Handheld
Hardware
Application V R
FOREMAN.qcif
NEWS.qcif
400 MHz XScale
64 MB flash
32 MB SDRAM
H.263 Encoder
H.263 Decoder
DES Crypto
11 MB with 300 frames
1:10(IP ratio),10(Quant),full search
Video Clips
DAQ board with
BNC Connector
Windows XP
1,000 samples/sec
Encryption consumes negligible
Energy as compared to encoding
Energy consumption of encryption is
negligible irrespective of video clips
Power Measurement System