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Analysis and Comparison of Fully Layered
Image Encryption Techniques and Partial Image
Encryption Techniques
Parameshachari B.D.1and K.M.S. Soyjaudah2
1Dept. of Electronics and Communication Engineering,
JSS Academy of Technical Education, Mauritius, Avenue Droopanath Ramphul,
Bonne Terre, Vacoas, Mauritius
parameshbkit@gmail.com
2Dept. of Electrical and Electronic Engineering, University of Mauritius, Reduit,
Mauritius
Abstract. In traditional image and video content protection schemes,
called fully layered, the whole content is first compressed. Then, the com-
pressed bitstream is entirely encrypted using a standard cipher (DES,
AES, IDEA, etc.). The specific characteristics of this kind of data (high-
transmission rate with limited bandwidth) make standard encryption
algorithms inadequate. Another limitation of fully layered systems con-
sists of altering the whole bitstream syntax which may disable some codec
functionalities. Partial encryption is a new trend in image and video con-
tent protection. It consists of encrypting only a subset of the data. The
aim of partial image encryption using SCAN mapping method is to re-
duce the amount of data to encrypt while preserving a sufficient level of
security than the fully layered image encryption using SCAN method. In
this paper, we analyzed Image encryption techniques and Partial image
encryption techniques and present the comparative results.
Keywords: Image Encryption, Mapping, Partial Image Encryption, Se-
curity, SCAN.
1 Introduction
Today with the rapid growth in the number of telecommunications and computer
networks as well as with the growing increase in the amount of multimedia trans-
mission, securing video content is becoming more important than ever before. A
traditional approach [1][2] for content access control is to first encode data with
a standard compressor and then to perform full encryption of the compressed
bitstream with a standard cipher. In this scheme called fully layered and the
compression and encryption processes are totally disjoint.
Another limitation of fully layered scheme consists of altering the original bit-
stream syntax. Therefore, many functionalities of the encoding scheme may be
disabled (e.g., scalability). Some recent works explored a new way of securing
the content, named, partial encryption or selective encryption, soft encryption,
K.R. Venugopal and L.M. Patnaik (Eds.): ICIP 2012, CCIS 292, pp. 599–604, 2012.
c
Springer-Verlag Berlin Heidelberg 2012
600 B.D. Parameshachari and K.M.S. Soyjaudah
perceptual encryption, by applying encryption to a subset of a bitstream. The
main goal of partial encryption is to reduce the amount of data to encrypt while
achieving a required level of security. An additional feature of selective encryp-
tion is to preserve some functionalities of the original bitstream (e.g., scalability).
The rest of this paper is organized as follows: Section 2 explains the related
work. The results are described in Section 3. This paper is concluded by provid-
ing the summary of the present work in Section 4.
2 Related Work
2.1 Image Encryption Techniques
A Technique for Image Encryption Using Digital Signatures : Aloka et al., [3]
have proposed a new technique to encrypt an image for secure image transmis-
sion. The digital signature of the original image is added to the encoded version
of the original image. Image encoding is done by using an appropriate error con-
trol code, such as a Bose-Chaudhuri Hochquenghem (BCH) code. At the receiver
end, after the decryption of the image, the digital signature can be used to verify
the authenticity of the image.
Lossless Image Compression and Encryption Using SCAN : Maniccam et al.,
[4] have presented a new methodology which performs both lossless compression
and encryption of binary and gray-scale images. The compression and encryption
schemes are based on SCAN patterns generated by the SCAN methodology. The
SCAN is a formal language-based two-dimensional spatial-accessing methodol-
ogy which can efficiently specify and generate a wide range of scanning paths or
space filling curves.
A New Encryption Algorithm for Image Cryptosystems : Chin-Chen et al., [5] use
one of the popular image compression techniques, vector quantization to design
an efficient cryptosystem for images. The scheme is based on vector quantiza-
tion (VQ), cryptography, and other number theorems. In VQ, the images are
first decomposed into vectors and then sequentially encoded vector by vector.
Then traditional cryptosystems from commercial applications can be used.
2.2 Partial Image Encryption Techniques
In this subsection, a few newly proposed techniques for partial image encryption,
which will improve the complexity of algorithm as well as make the key stronger
has been introduced.
Partial Encryption Algorithms : Cheng et al., [6] proposed partial encryption
methods that are suitable for images compressed with two specific classes of
compression algorithms: (a) quadtree compression algorithms, and (b) wavelet
compression algorithms based on zero trees.
Analysis and Comparison of FLET and PIET 601
Selective Encryption Methods for Raster and JPEG Images : Droogenbroeck et
al., [7] proposed the selective encryption methods for uncompressed (raster) im-
ages and compressed (JPEG) images. According to Droogenbroeck et al., at least
4-5 least significant bitplanes should be encrypted to achieve the satisfactory vi-
sual degradation of the image.
Selective Bitplane Encryption Algorithm : Podesser et al., [8] proposed a selective
encryption algorithm for the uncompressed (raster) images, that is quite oppo-
site from the first method by Droogenbroeck et al., [7]. In the raster image that
consists of 8 bitplanes, Schmidt and Uhl’s algorithm encrypts only the most sig-
nificant bitplanes. The proposed underlying cryptosystem for this method was
AES. However, without loss of generality, any fast conventional cryptosystem
may be chosen instead.
On Partial Encryption of RDF-Graphs : In 2005, Mark et al., [9], proposed
a method to partially encrypt RDF-graphs. It differs from other approaches in
that the result is a single self-describing RDF compliant graph containing both
encrypted data and plain text data. The method allows for fine grained encryp-
tion of subjects, objects, predicates and sub graphs of RDF graphs.
Selective Image Encryption Using JBIG : In 2005, Roman et al., [10],proposed
selective encryption of JBIG encoded visual data exploiting the interdependen-
cies among resolution layers in the JBIG hierarchical progressive coding mode.
Contrasting to earlier ideas when selectively encrypting a subset of bitplanes,
they able to show attack resistance even in case of restricting the amount of en-
cryption to 1% - 2% of the data only. The extremely low amount of data required
to be protected in their technique also allows the use of public-key cryptography
thereby simplifying key management issues.
A Partial Image Encryption Method with Pseudo Random Sequences : In 2006,
Y.V. Subba Rao et al.,[11], proposed partial encryption of image using pseudo
random sequences with simple hardware. According to [11] partial encryption
method achieves the same security with the improvement in processing speed.
The performance of the method mainly depends on the differentiation of corre-
lated and uncorrelated information in the image. Here we have treated the MSB
planes as correlated information.
Region-Based Selective Encryption for Medical Imaging : In 2007, Yang et al.,
[12], proposed two novel region-based selective encryption schemes for medical
imaging. The first scheme is to randomly invert the first two MSBs of ROI
coefficients in wavelet transform domain. It can be efficiently implemented and
only incurs little compression efficiency overhead, also it can be extended to other
motion formats. The second scheme, selective encryption of the compressed ROI
data, provides a high level security and has no file size changes.
Selective Encryption of Multimedia Images : In 2008, Nidhi et al., [13], pro-
poses a selective encryption technique in wavelet domain for conditional access
602 B.D. Parameshachari and K.M.S. Soyjaudah
Tabl e 1. Processing Time for Fully Layered Encryption and Partial Image Encryption
for Different Image Sizes
Image Size Fully Layered Encryption Using Partial Image Encryption SCAN
SCAN Method(second) Mapping Method(second)
457X700 1.230 1.065
500X446 0.847 0.652
400x568 0.706 0.521
434x823 1.333 1.101
Tabl e 2. Memory usage for Fully Layered Encryption and Partial Image Encryption
for Different Images
Image Fully Layered Encryption Partial Image Encryption
Using SCAN SCAN Mapping
Method(bytes) Method(bytes)
Radiological image(gray scale) 1112004 0900112
Radiological image(color) 1224125 1004105
Lena(gray scale) 2406239 2009106
Lena(color) 2709752 2100219
Coffeemaker (grayscale) 4709605 4201517
Coffeemaker (color) 5206807 4711302
Tabl e 3. Results of Fully Layered Encryption using SCAN Method and Partial Image
Encryption SCAN Mapping Method for Gray Scale Images
Image Amount Image Reconstructed
Correlation Image Correlation
Radiological image Fu l l 0.0067 0.999918
25% 0.0575 0.999952
8.5% 0.2367 0.999976
2.5% 0.1978 0.999987
Lena Full 0.0023 0.999998
25% 0.0304 0.999926
8.5% 0.0745 0.999915
2.5% 0.1987 0.999968
Coffeemaker Ful l 0.0085 0.999971
25% 0.0786 0.999941
8.5% 0.3456 0.999986
2.5% 0.5483 0.999974
systems. The encryption is applied only to a subset of multimedia data stream
rather than the multimedia data in its entirety to save the computational time
and computational resources. According to [13], encryption technique controls
Analysis and Comparison of FLET and PIET 603
Tabl e 4. Results of Fully Layered Encryption using SCAN method and Partial Image
Encryption SCAN mapping method for Color Images
Image Amount Image Reconstructed
Correlation Image Correlation
Radiological image Fu l l 0.0095 0.999911
25% 0.0589 0.999919
8.5% 0.2014 0.999925
2.5% 0.1245 0.999963
Lena Full 0.0012 0.999921
25% 0.0201 0.999902
8.5% 0.0541 0.999901
2.5% 0.1252 0.999923
Coffeemaker Ful l 0.0076 0.999989
25% 0.0532 0.999962
8.5% 0.3135 0.999976
2.5% 0.5012 0.999912
the transparency and security in an efficient manner by selecting the coefficients
for encryption based on predefined criteria.
3 Results and Discussion
In this paper image processing software package MATLAB 7.0 is used as the
engine for the image processing experiments for fully layered image encryption
and partial image encryption techniques. An RGB image is stored in MATLAB
as an M-by-N-by-3 data array that defines red, green and blue color components
for each individuals pixel. The color of each pixel is determined by the combina-
tion of the red, green and blue intensities stored in each color plane at the pixels
location. Images that were used during full layered encryption as well as used
during partial image encryption these experiments shows that the partial image
encryption method as given best results than fully layered image encryption.
As the comparative results of partial image encryption using SCAN mapping
method given best results than the fully layered image encryption using SCAN
method[14]asshownintables.
4 Conclusions
As combined and effective methods has been proposed in this paper for fully lay-
ered image encryption using SCAN method and partial image encryption using
SCAN mapping method. Many of the proposed schemes only achieve moderate
to low level of security which may find applications in which quality degradation
preferred over absolute security. Partial image encryption using SCAN mapping
method provided higher security, flexibility, multiplicity, spatial selectively and
format compliance than fully layered image encryption.
604 B.D. Parameshachari and K.M.S. Soyjaudah
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