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ENCRYPTED FUSION OF FACE AND IRIS BIOMETRICS
Sivasankari Narasimhan
Assistant Professor, Electronics and Communication Engineering,
Mepco Schlenk Engineering College, Virudhunagar Dt, (India).
E-mail: sivani.sivasankari@gmail.com
ORCID: https://orcid.org/0000-0002-3162-4751
Muthukumar Arunachalam
Associate Professor, Electronics and Communication Engineering,
Kalasalingam University, Virudhunagar Dt, (India).
E-mail: Muthuece.eng@gmail.com
ORCID: https://orcid.org/0000-0001-8070-3475
Recepción: 28/11/2019 Aceptación: 17/03/2021 Publicación: 30/11/2021
Citación sugerida:
Narasimhan, S., y Arunachalam, M. (2021). Encrypted fusion of face and iris biometrics. 3C Tecnología.
Glosas de innovación aplicadas a la pyme, Edición Especial, (noviembre, 2021), 513-535. https://doi.
org/10.17993/3ctecno.2021.specialissue8.513-535
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ABSTRACT
Security is the main concern in storing databases. Any methods can be used to secure the
data. In addition to that identication also done to provide the correct service to the person.
In our model we propose the methodology to include biometric fusion and encryption
to store and secure user’s information. Image fusion is done from the information from
dierent face and iris images. The method of considering only high intensity pixel based
image fusion generate new images that hold the attractive information and characteristics
of each input image. The fused resulting image is given to the encryption module and
encrypted information in stored in database which is further used for identication
and authentication. Fusion techniques and lightweight encryption algorithm has been
implemented and simulated in MATLAB. The parameters correlation, computation time,
Unied averaged changed intensity(UACI), Number of changing pixel rate(NCPR)and
Entropy are calculated and the results show the eectiveness of encrypted fusion based on
DWT. Entropy has been increased by 67%. NCPR of 99.6239 and UACI of 3.3004.
KEYWORDS
Fusion, Face biometric, Iris biometric, DWT, Encryption.
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1. INTRODUCTION
Image fusion is an essential step in multimodal biometrics. Image fusion is a process by
which two images are fused together to obtain a single image. Images with dierent focused
regions, images from dierent modalities or images taken in dierent times have been
fused together to give enhanced results. With change in time, the face images produced
by persons may dier due to aging. These images cannot give a clear picture needed for
clear identication. Thus, for ecient diagnosis, one needs dierent multimodal image
information in a single image. The features that are not changes more with age is iris. To
this point, in research, many fusion techniques based on Iris and face images, were proposed
by the researchers. The transform based fusion methods include decomposition of image
by Stationary Wavelet Transform (SWT), Discrete Wavelet Transform (DWT), Lifting
Wavelet Transform (LWT), Redundancy Discrete Wavelet Transform (RDWT), Dual-Tree
Complex Wavelet Transform (DTDWT). These methods have unique drawbacks but all
of them share some common drawbacks such as introduced additive noise in fused image.
A multimodal biometric system is developed using ngerprint and iris biometric in Rajbhoj
and Mane (2015). The system combines ngerprint and iris at feature level. Single feature
vector is obtained by fusing ngerprint and iris image and unique textural pattern from
fused image is obtained by ecient wavelet transform. Matching is carried using Hamming
distance. Here independent databases are used for face and iris images and each ngerprint
is assigned a corresponding iris image.
The multimodal biometric system in ElAlami, Amin, and El-Al (2012) combines face and
ngerprint biometrics in matching score level. They used the gray-level co-occurrence matrix
(GLCM) as an eective method for extracting the texture features in the face recognition
and crossing number method is used for ngerprint feature extraction. For matching process
they used correlation coecient as the similarity measure. A multimodal biometric system
is developed by combining face and ngerprint biometric by score level fusion. According
to \cite{19} face recognition is done using PCA and ngerprint recognition is done using
minutiae matching and Gabor ltering.
A multimodal biometric system in Krishneswari and Arumugam (2012) combines palm
print and ngerprint in feature level. Palm print and nger print images were fused using
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wavelet based image fusion techniques with min-min approximation. Features were extracted
using Discrete Cosine Transform (DCT) and feature reduction is done. In their work also
independent databases are used for palm print and ngerprint and they are combined
by assigning a ngerprint image to each palm print image. Their shows that multi modal
biometrics are more ecient than conventional palm print based methods.
Usman et al. (2017) explains about, light weight encryption algorithm which will t for IoT.
The single input image is authenticated using encryption algorithm.
In the proposed method, source images are decomposed into low-level sub band, high-level
sub bands using DWT. Next, low-level sub-images are again decomposed into low and high
level images. In two level decomposition, iris image is fused.
Our project gives the following signicant works
1. Dual modal biometric as face and iris recognition fusion have been taken.
2. Encryption to safeguard the fused database.
3. Analysis of security concerns in both fusion and encryption.
The remaining sections are organized as follows: section 2 provides the proposed methods
and section 3 gives the implementation results followed by conclusion in section 4.
2. PROPOSED METHODOLOGY
The proposed DWT consists of four steps: Enhancement, decomposition, fusion and
encryption. The block diagram of the proposed DWT-based face iris fusion is shown in
Figure 1. Now let us see the process involved and used components in the process one by
one.
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Figure 1. Overall block diagram.
Source: own elaboration.
Step1: Face image and iris images are preprocessed. Color images are converted into gray
scale images. They have been resized into 256x256
Step 2: As per Discrete Wavelet Transform (DWT), approximation, horizontal, vertical
and diagonal details have been found out for two levels for both images. The individual sub
images are compared and the highest intensity value image is taken for fused image.
Step 3: The image is encrypted using secure light weight encryption algorithm.
2.1. DWT ALGORITHM
The Haar wavelet illustrates the desirable properties of wavelets in general. It can
generally use for image denoising. It uses the orthonormal basis vector in the rows of
. DWT demonstrates the localization: the rst row (1,1,1,1) term gives
the average signal value; Second row (1,1,-1,-1) places the signal in the left side of the
domain; and (1,-1,0,0) places it at the left of the left side. The explanation of DWT is
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available in “Discrete wavelet transform” (2008). First, the samples are passed through a
low pass lter with impulse response g (n), Hence the convolution operation between input
image function and impulse function has been taken place.
(1)
The signal is decomposed simultaneously using high pass lter (h). So, the two lters are
related to each other and they are known as a quadrature mirror lter.
(2)
(3)
With the sub sampling factor 2, the process is continued and all the levels are cascaded.
For the representation of images in multi resolution wavelets can be used. If it has to be
converted into other domain, the properties in one domain are easily separable and scalable.
There is a unique set of expansion coecients in every representable function of Fourier
kernals.
2.2. FUSION
The performance of biometric system is improved by choosing correct fusion. In our
approach feature level fusion is used. The feature vectors at second level of DWT are
combined to produce the fused image. For verication of individual persons biometric,
dierent images of any biometric can be fused. But authentication purpose, two dierent
biometrics have been connected.
2.3. ENCRYPTION
Various encryption algorithms are being developed still now. For message encryption
Symmetric encryption algorithm is used. In our algorithm, due to space complexities,
light weight encryption algorithm is used. Usually, encryption operation is performed with
specied number of bits known as key. With a 64 bit initial key further rounds of keys are
generated. Key expansion is done as per the logic provided by Usman et al. (2017). The
initial key is set as AAAAAAAAAAAAfor this algorithm. It can be expanded for next
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rounds. The key expansion diagram is shown in Figure 2. The confusion and diusion are
introduced by ‘F’ function in it.
16 Bits 16 Bits16 Bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
4
bits
64 Bits
16 Bits
F-function F-function F-function F-function
K1 K2 K3 K4
4x4
Matrix
4x4
Matrix
4x4
Matrix
4x4
Matrix
K5
Kb1fKb2f Kb3fKb4f
Ka1fKa2f Ka3fKa4f
Km1Km2Km3Km4
Figure 2. Key expansion.
Source: (Usman et al., (2017).
As per the gure, from the initial key K5 is derived as XOR function of K1, K2, K3, K4. The
function ‘F’ has done some permutations which gets 16 bits input and 16 bit output. Then
encryption process is done as per equation 6. The intermediate ciphertext is given as:
; (4)
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ICi,j is the intermediate result. Px i,j is the plaintext. If j=1 or 4 rst equation is performed.
If j=2 second operation is performed. If j=3 third operation is done. The nal encryption
operation is performed as the concatenation result of fth round.
(5)
The encrypted information is stored in database, further it is used for identication.
4. IMPLEMENTATION RESULTS
Yale database is taken for face image in our experiment, which contains 15 subjects each of
which have 15 images under dierent postures. The size of the image is 320 x 243. CASIA
database is taken for iris images which contains 36 iris subjects and 7 for each. For our
experiments, rst 7 images of face are merged with rst 15 images of IRIS database.
Figure 3. FACE DWT segment image.
Source: own elaboration.
First both face and iris images are undergone for DWT segmentation. The segmented
image is shown in Figures 3 and 4.
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Figure 4. IRIS DWT segment image.
Source: own elaboration.
The images are getting fused by highest intensity feature level fusion logic. The fused image
is shown in Figure 5.
Figure 5. Fused image.
Source: own elaboration.
But fused image is intermediate stage. It is not visible by anybody. This image is going for
encryption. In our algorithm, we are using light weight encryption algorithm. Hence it
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can be used for chip implementation. The fused image is resized to 256x256 image. After
encryption we got the image as given in Figure 6.
Figure 6. Encryption and Decryption by correct key.
Source: own elaboration.
When the same user is used for authentication the correlation score should be high. The
encrypted image and original image are shown with their histograms in Figure 7.
Figure 7. Correlation of original and encrypted image.
Source: own elaboration.
Original
Original
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Now, the image correlation and entropies have been calculated. The scatter plot of image
is given in Figure 8.
Figure 8. Scatter plot of encrypted image.
Source: own elaboration.
4.1. EVALUATION PARAMETERS
Image Entropy: the encryption algorithm adds extra information to the data so as to
make it dicult for the intruder to dierentiate between the original information and the
encrypted information. Entropy is dened as:
(6)
How much entropy is higher, more in formations are present, and hackers cannot nd it
easily. The results for the 35 image fusion are given in Table 1. Average of 7.7512 for the
encrypted image is obtained. Almost 69% of entropy is increased, compared with original
fused image.
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Correlation: dependency of statistical relationship between two images is said to be
correlation. A well-designed cipher should not possess any relationship with original
message.
In our experiment the correlation coecient is calculated for original fused message and
encrypted images. The correlation coefcient is dened as:
(7)
where cov(x, y), D(x) and D(y) are covariance and variances of variable x and y directions
respectively. For ideal cipher case γ should be equal to 0 and for the worst case γ will be
equal to 1.
In our experiment the original fused image has correlation coecient of 0.98157, whereas
the encrypted images have -0.109 correlation coecient. (They are negatively correlated).
Number of changing pixel rate (NCPR): this is the parameter for testing the encryption
against dierential attacks. As per Wu, Noonan and Agaian (2011) the range of percentage
is [0-100]. When it is zero it remains that all the pixels are having the same value. Clearly
NCPR concentrates on absolute number of pixels which changes values in dierential
attacks.
(8)
Where C1, C2 are the before and after one pixel image in cipher.
(9)
T denotes the total number of pixels in ciphertext. The average value we obtain for NCPR
is 99.6239.
Unied averaged changed intensity (UACI):
UACI concentrates on the averaged dierence between two paired ciphertext images.
(10)
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Where F is the maximum supported pixel value compatible with the cipher text. In our
experiment F is taken as 255. The average value we obtained from this as 3.3004
Table 1. Analysis of parameters with key ‘AAAAAAAAAAAAAAAA’.
Image 1 Image 2
Correlation Total
Encryption
time (ms)
NCPR
(%) UACI (%)
Entropy
Original
Image
Encrypted
Image
Original
image
Encrypted
image
Subject 1.
glasses
Iris 1 0.9782 -0.0206 9.172 99.661 3.082 4.124 7.9318
Iris 1b 0.9751 -0.0246 8.113 99.653 2.2138 4.2116 7.9311
Iris 1c 0.9848 -0.0048 8.096 99.597 3.8024 4.2159 7.9152
Iris 1d 0.9689 -0.0138 8.165 99.676 1.6850 4.2351 7.9251
Iris 1e 0.9831 -0.0138 8.093 99.679 3.4871 4.2117 7.9319
Iris 1f 0.9800 -0.0168 8.453 99.557 2.4720 4.3174 7.9716
Subject 2.
glasses
Iris 2 0.9831 -0.0058 8.003 99.565 3.8076 4.2263 7.2146
Iris 2b 0.9817 -0.0014 8.158 99.623 3.7036 4.2247 7.2308
Iris 2c 0.9737 -0.0096 8.034 99.586 1.8903 4.2126 7.2310
Iris 2d 0.9737 -0.0096 9.002 99.586 1.8903 4.2329 7.5151
Iris 2e 0.9845 -0.0077 8.197 99.627 4.0569 4.2352 7.4151
Iris 2f 0.9795 -0.0021 8.232 99.632 2.6016 4.1247 7.5309
Subject 3.
glasses
Iris 3 0.9821 -0.0139 8.358 99.632 2.6081 4.2147 7.9308
Iris 3b 0.9856 -0.0071 8.264 99.577 3.1991 4.2146 7.9310
Iris 3c 0.9854 -0.0142 8.875 99.636 3.1645 4.2359 7.9151
Iris 3d 0.9854 -0.0142 8.270 99.636 3.1645 4.2359 7.9151
Iris 3e 0.9798 -0.0100 8.522 99.630 2.4692 4.2147 7.9309
Iris 3f 0.9889 -0.0115 8.415 99.638 4.5532 4.3374 7.9726
Iris 3g 0.9880 -.0169 8.679 99.676 3.9941 4.2663 7.9146
Subject4.
glasses
Iris 4 0.9804 -0.0124 8.508 99.600 3.3139 5.1418 7.9561
Iris 4b 0.9804 -.0167 8.426 99.638 3.1778 5.0205 7.9314
Iris 4c 0.9804 -.0167 8.426 99.638 3.1778 5.0205 7.9314
Iris 4d 0.9804 -0.0167 8.8108 99.638 3.1778 5.0205 7.9314
Iris 4e 0.9795 -0.0102 8.8440 99.658 3.8139 5.2303 7.9743
Iris 4f 0.9808 -0.0152 9.0458 99.627 4.0870 5.2835 7.9536
Iris 4g 0.9801 -0.0167 9.1555 99.615 4.1067 5.2935 7.9506
Subject05.
glasses
Iris 5 0.9822 -0.0037 9.0337 99.624 3.5343 5.0542 5.0542
Iris 5b 0.9848 -0.0039 9.0955 99.551 4.0488 5.0956 7.9943
Iris 5c 0.9833 -0.0091 9.1250 99.644 3.4544 4.8371 7.9641
Iris 5d 0.9833 -0.0091 9.0839 99.644 3.4544 4.8371 7.9641
Iris 5e 0.9837 -0.0050 8.8077 99.679 3.4289 4.7934 7.9699
Iris 5f 0.9855 -0.0030 9.1667 99.575 4.1457 5.1360 7.9884
Iris 5g 0.9855 -0.0030 8.8251 99.575 4.1457 5.1360 7.9884
Source: own elaboration.
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This work has been accomplished with rst image of yale database and CASIA database of
second image. Various parameters have analyzed in this methodology and the parameters
are given in Table 1.
Key sensitivity: all encryption algorithms have to be designed in such a way that, if one
bit is changed almost 60 % of the data should be changed in ciphertext. The changes in
seed key value for the same biometric subjects are taken and the result is compared in Table
2. The distribution of histogram is given in Table 3.
Table 2. Comparison of various keys to show the key sensitivity.
Image Image 2 Key
Correlation of
Original fused
Image
Correlation
of Encrypted
Image
Total
Encryption time
(ms)
((NCPR) (UACI)
Subject 1
glasses Iris 1 AAAAAAAA
AAAAAAAA 0.9782 -0.0206 9.172423 99.66 3.082
Subject 1
glasses Iris 1 ABACADAE
AFAA1234 0.9796 -0.0134 10.920902 99.6363 3.1735
Subject 3
glasses Iris 3 ABACADA
EAFAA1234 0.0110 0.9867 8.282109 99.6323 3.4111
Source: own elaboration.
Table 3. Comparison of different correlation histograms and scatter diagrams.
Biometric-1 Biometric-2 Correlation Histogram Scatter diagram of encryption
Yale- subject 1
with glasses Iris 1.a
subject 1 with
glasses Iris 1.b
Original
Original
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subject 1 with
glasses Iris 1c
subject 1 with
glasses Iris 1d
subject 1 with
glasses Iris 1e
subject 1 with
glasses Iris 1f
Subject 2with
glasses Iris 2a
Original
Original
Original
Original
Original
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subject 2 with
glasses Iris2b
Subject 2 with
glasses Iris2c
subject 2 with
glasses Irsi 2d
Subject 2with
glasses Iris2e
subject 2 with
glasses Iris 2f
Original
Original
Original
Original
Original
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Subject3
glasses Iris 3a
Subject3
glasses Iris 3c
Subject3
glasses Iris 3d
Subject3
glasses Iris 3e
Subject3
glasses Iris3f
Original
Original
Original
Original
Original
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Subject3
glasses Iris 3g
Subject4
glasses Iris 4a
Subject4
glasses Iris 4b
Subject4
glasses Iris 4c
Subject4
glasses Iris 4d
Original
Original
Original
Original
Original
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Subject4
glasses Iris 4e
Subject4
glasses Iris 4f
Subject4
glasses Iris 4g
Subject05
glasses Iris 5a
Subject05
glasses Iris 5b
Original
Original
Original
Original
Original
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Subject05
glasses Iris 5c
Subject05
glasses Iris 5d
Subject05
glasses Iris 5e
Subject05
glasses Iris 5f
Subject05
glasses Iris 5g
Source: own elaboration.
Original
Original
Original
Original
Original
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5. CONCLUSIONS
In this algorithm, a feature level fusion method to fuse the two biometrics is introduced.
Encryption algorithm to do the operations in a simple manner without the need of S-box
is performed for fused image. Finally, the security parameters such as entropy, correlation,
computation time, Unied averaged changed intensity, Number of changing pixel rate are
calculated. As a future scope, this logic can be implemented with some public key algorithms
to implement in ATM.
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wavelet_transform
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Krishneswari, K., & Arumugam, S. (2012). Multimodal Biometrics using Feature
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