1. An Experimental Study on Energy Consumption of Video Encryption for Mobile Handheld Devices
Kyoungwoo Lee, Nikil Dutt, and Nalini Venkatasubramanian
Center for Embedded Computer Systems
Donald Bren School of Information and Computer Sciences
University of California, Irvine
<kyoungwl, dutt,

2. Introduction Motivation Problem
Mobile multimedia applications are vulnerable
to security attacks in wireless networks
Significant computation for video encryption is
expected on battery-operated mobile devices
Problem
Evaluate symmetric video encryption schemes
from the perspective of energy consumption
both analytically and experimentally

3. Secure Video Application
Battery
-Operated
Devices
Raw
Video
Video Encoder
Motion
Estimation
Quantization
DCT
Entropy
Encoding
Attacks
Compressed
Bit Stream
Insecure
network
Symmetric
Encryption
Technique
Encrypted &
Compressed
Bit Stream
Secure Video Encoder
Video Decoder
Battery
-Operated
Devices
This is the general block diagrams of video encoder and video decoder.
Usually video encryption is done after encoding and video decryption before decoding. Here are typical secured video conferencing steps. But some algorithms such as Zig-Zag permutation is applied between quantization and entropy encoding in Encoder.
Entropy
Decoding
Inverse
Quantization
IDCT
Motion
Compensation
Compressed
Bit Stream
Decompressed
Bit Stream
Symmetric
Decryption
Technique
Encrypted &
Compressed
Bit Stream
Secure Video Decoder

4. Video Encryption Schemes
Naïve Encryption Scheme
Selective Encryption Scheme
Zig-Zag Permutation Scheme
Video Encryption Algorithm (VEA)
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
#P(&*(UV
Encrypt
Decrypt
plaintext
ciphertext
network
Briefly I’ll review video encryption algorithms and compare them. They are Naïve Algorithm, Selective Algorithm, Zig-Zag Permutation Algorithm, Video Encryption Algorithm, and sign-bit Encryption Algorithm.

5. Studied Video Encryption Schemes
(1) Naive Encryption Scheme
I-frame
P-frame
Naive
Encryption
(DES)
Video
Encoding
(H.263)
EnergyNaive=eDES*STotal
eDES - energy to encrypt one byte by DES
STotal - size of the whole video data
EnergySelective = eDES*SIB
SIBl - size of Intra-blocks in video data
Intra-block
I-frame
P-frame
Selective
Encryption
(DES)
Video
Encoding
(H.263)
(2) Selective Encryption Scheme
Naïve Algorithm encrypts the entire video streams like a text. This is very secure but slow comparing with others. But the size of encrypted video stream doesn’t change like other algorithms.

6. Studied Video Encryption Schemes (cont’)
EnergyZig-Zag = eoverhead
eoverhead - energy to shuffle coefficients
I-frame
P-frame
Video Encoding
& Zig-Zag Permutation
(H.263 & Shuffle)
(3) Zig-Zag Permutation Scheme
eXOR - energy for XOR
EnergyVEA = ½*(eDES+eXOR)*STotal
I-frame
P-frame
VEA
(XOR & DES)
Video
Encoding
(H.263)
(4) Video Encryption Algorithm (VEA)

7. Comparison of Video Encryption Schemes
Analytical Comparison
Algorithm
Drawback
Relative
Energy
Naive
Significant
Computation
100 %
Selective
Moderate
Security
59 %
Zig-Zag
Breaks efficiency
of Video Encoding
< 1 %
VEA
Not applicable
for H.263 without
even distribution
50 %
Naïve encryption scheme consumes twice
the energy of Selective encryption scheme

8. Power Measurement System
Experimental Setup
Experimental Setup
System Architecture
PZaurus = * VZaurus VR R
Secure Video Application
(Encoder / Decoder)
DES
H.263
Codec
Device
Driver
5 V V
Zaurus
OpenSSL
Library
R = 22 ohm
Operating System
(Linux) V R
Mobile Handheld Hardware
(Sharp Zaurus)
DAQ board with
BNC Connector
Windows XP
1,000 samples/sec
400 MHz Intel XScale
64 MB flash & 32 MB SDRAM
Power Measurement System

9. Energy Consumption for Varying Quality and Security
(Quant Scale)
Security
(Full vs. Partial)
Measured
Energy (J)
Energy
Overhead
High
(Quant = 1)
High (Full)
128.2
13 %
Low (Partial)
111.0
Mid-High
(Quant = 4)
High (Full)
92.05
9 %
Low (Partial)
83.56
Mid-Low
(Quant = 10)
High (Full)
77.62
2 %
Appropriate for
mobile video
Low (Partial)
75.78
Low
(Quant = 31)
High (Full)
70.44
1 %
Low (Partial)
69.89
Energy overhead for full encryption is NEGLIGIBLE

10. Experimental Results: Video Coder & Crypto80
74.77 70 60
Huge
Difference
(98 %) 50
Measured Energy (Joules) 40 30 20
11.37 10
1.5
Application
H.263 Encoder
H.263 Decoder
DES Crypto
Encryption consumes negligible
energy as compared to encoding

11. Experimental Results: Video Encryption
Negligible Energy Overhead 90
77.62 80
74.77
75.78
72.87
74.11
72.26
(2.4%) 70
(1.7%) 60
Measured Energy (Joules) 50
Encoding without Encryption 40
Encoding with Encryption (Selective)
Encoding with Encryption (Naïve) 30 20 10
FOREMAN.qcif
NEWS.qcif
11 MB with 300 frames
1:10(IP ratio),10(Quant),full search
Video Clips
Energy consumption of encryption is
negligible irrespective of video clips