Multi-Biometric Authentication through Hybrid Cryptographic System

Integrated Intelligent Research (IIR) International Journal of Computing Algorithm
Volume: 04 Issue: 01 June 2015 Pages:19-21
ISSN: 2278-2397
19
Multi-Biometric Authentication through Hybrid
Cryptographic System
M.Gobi,1
R.Sridevi2
1
Assistant Professor in Computer Science, Chikkanna Government Arts College, Tiruppur, India
2
Research Scholar in Computer Science, Government Arts College, Udumalpet, India
Email: mgobimail@yahoo.com, srinashok@gmail.com
Abstract – In most of the real time scenario, authentication is required
very much so as to enable the person to access a private database of
any type. Researchers have started using biometric traits for the
authenticity of a person. The various biometrics traits available are
face, iris, palm print, hand geometry, fingerprint, ear etc., But the
application that uses a single biometric trait often have to challenge
with noisy data, restricted degrees of autonomy, non-universality of
the biometric trait and intolerable error rates. Multi biometric systems
seem to lighten these drawbacks by providing multiple verification of
the same personality. Biometric fusion is the use of multiple biometric
inputs or methods of processing to improve performance. In this
paper, a novel combination of Multi biometric fusion, Symmetric
Cryptography and Asymmetric Cryptography is proposed. A fused
biometric image is encrypted using Advanced Encryption Standard
whose secret key is in turn encrypted using elliptic curve
cryptography which is considered as one of the efficient Asymmetric
cryptographic algorithms. As the symmetric cryptographic algorithms
involve in key exchange mechanism, the secret key is proposed to be
secured by using ECC. Hence, the system proposed is expected to be
more secured to store the biometric traits of an individual.
Keywords—Biometric Images; Image Fusion; Elliptic Curve
Cryptography; Security; Privacy.
I. INTRODUCTION
Private data in real time applications which involve financial
transactions and highly regulated to information zone are
portrayed to be very confidential to make it available to the
authenticated person. This data tend to be kept very secret so as
to measure the identity of an individual. So many methods
were proposed to keep this information confidential. Private
databases were proposed which can be accessed using ID
numbers or password that amounts to knowledge based
security. Sometimes the intruders or hackers may well infringe
the flap of security. Many cryptographic algorithms are
available to protect the private data of an individual. Both
symmetric and asymmetric algorithms ensure the
confidentiality and privacy of data in different ways.
Symmetric algorithms are proved to be better for large data
when asymmetric stands for smaller one. Even though one
algorithm outperforms the other algorithm, it is always
necessary to identify the right algorithm for the right
application. Elliptic curve cryptography is one such public key
cryptographic algorithm based on the elliptic curves and uses
the location of base points on an elliptic curve to secure
information. ECC make use of a relatively short encryption key
to decode an encrypted message because the short key is
comparatively faster and involves less computing power than
other asymmetric cryptographic algorithms. Biometric systems
were also proposed to provide knowledge based security
enhancement over the years of research scenario. Biometric
technologies are the automated methods of classifying or
authenticating the identity of a person based on a biological or
social characteristic. There are various biometric traits like
face, fingerprint, iris, palm print, hand geometry and ear etc., in
which some of them can be, used for security systems[1-3].
Uni-model biometric systems support one biometric trait taken
for recognizing or identifying an individual wherein
multimodal biometric systems enable the fusion of two or more
biometric images with various levels of integration. In this
paper, a multimodal biometric fusion [4] [5] which hides a
person’s fingerprint under the face image is considered.
Though these two biometric traits perform better individually,
they fail under certain conditions when used as a uni-modal
trait. The problem arises at the time of acquisition of
fingerprint images with low quality. Poor quality face image
may also create problem of identifying a right person.
Therefore these two traits are fused together to make a person’s
identity better than before. The fused image is encrypted to
increase the privacy of the data stored in the private database.
II. METHODOLOGIES
A. Biometric Image Fusion
Biometrics is programmed methods of identifying a person
based on a physiological or behavioral characteristic.
Biometric features normally stated are face, fingerprints, hand
geometry, iris, retina, vein, and voice. Since Biometric data are
distinct from personal information, these cannot be reverse-
engineered to refabricate personal information. They cannot be
whipped and used to access the personal information. Although
biometric technology has been popular for many years, modern
developments in this incipient technology, attached with other
security algorithms, now make biometrics efficiently used for
security reasons [6]. Image fusion is a technique that can be
done in many ways. A simple method of image fusion is
followed in this work, where the two images are taken as such
they both have same pixel dimensions. Then the fusion of these
images is done as follows:
Step 1: Read two input images, fingerprint and face images in a
buffered image array.
Step 2: Load the images onto the input array.
Step 3: Measure the width and height of each image to check
for the same dimensions.
Step 4: Draw each of the input images onto the output image.
Step 5: Create the output image file and write the output image
to it.
Step 6: Display the output image.
B. Advanced Encryption Standard Algorithm
AES is a block cipher with a block length of 128 bits. AES
allows for three different key lengths: 128, 192, or 256 bits.

ISSN: 2278-2397
20
Encryption consists of 10 rounds of processing for 128-bit
keys, 12 rounds for 192-bit keys, and 14 rounds for 256-bit
keys. Except for the last round in each case, all other rounds
are identical. Each round of processing includes one single-
byte based substitution step, a row-wise permutation step, a
column-wise mixing step, and the addition of the round key.
The order in which these four steps are executed is different for
encryption and decryption. Although, overall, the same steps
are used in encryption and decryption, the order in which the
steps are carried out is different, as mentioned previously[7].
The overall structure of AES encryption/decryption is shown in
Fig 1.
Fig 1. AES Encryption and Decryption
C. Elliptic Curve Cryptography Algorithm
1) Key Generation:
Key generation is an important part where we have to generate
both public key and private key. Here, Elliptic curve
cryptography algorithm is used to generate both of these keys.
The encryption of the fused image is done using a public key
and the same will be decrypted using the corresponding private
key. For this key pair generation, select a number d, within the
range of ‘n’, which is the random number representing the
maximum limit. Using the following equation, the public key,
Q can be generated.
Q = d * P (1)
d = the random number that we have selected within the range
of (1 to n-1).
P is the point on the curve.
Q is the public key
D is the private key.
2) Encryption & Decryption:
The Elliptic Curve Integrated Encryption Scheme is as follows
[12].To encrypt the AES Secret Key,
Step 1: Select a random integer r in [1, n– 1]
Step 2: Compute R = rG
Step 3: Compute K = hrQB = (Kx, Ky), checks that K ≠ 0
Step 4: Compute keys k1||k2 = KDF(Kx)
Where KDF is a key derivation function.
Step 5: Compute c = ENCk1(m)
Where m is the text file of fused image
Step 6: Compute t = MACk2(c)
Where MAC is message authentication code
Step 7: Store (R, c, t) in the database for decryption.
To decrypt AES Secret Key,
Step 1: Perform a partial key validation on R
(Check if R ≠ 0, check if the coordinates of R
are properly represented elements in Fq and
Check if R lies on the elliptic curve defined by
a and b)
Step 2: Compute KB = h.dB.R = (Kx, Ky ) ,
Check K ≠ 0
Step 3: Compute k1, k2 = KDF (Kx)
Step 4: Verify that t = MACk2(c)
Step 5: Compute m = ENCK1-1(c)
K = KB, since K = h.r.QB = h.r.dB.G
= h.dB.r.G = h.dB.R = KB
III. PROPOSED SYSTEM
A system is proposed to enhance the privacy, confidentiality
and integrity of an individual with the biometric traits to access
the private data stored in the database. It also verifies the
authentication by checking biometric traits with the previously
stored biometrics in the database. The system of Image
Processing and Cryptography join hands together to intensify
the secrecy of private data which is to be kept confidential [8].
This includes
A. Multi biometric Image Fusion
B. Fused Image Encryption using AES
C. Encryption of AES Key using ECC
D. Decryption of AES Key
E. Decryption of Fused Image.
The biometric images after encryption along with the encrypted
AES key are sent to the receiver. At the receiver end, the
encrypted key is first decrypted to get the secret key. Then this
secret key is used to decrypt the biometric images. To access
the confidential information like bank account details, patient
history or health insurance details, biometric images are to be
scanned for authentication. They are compared with the images
already stored. This allows no other than the authenticated
person to access the private and confidential details [9] [10].
The system is explained in Fig 2.
Fig 2.Proposed System of Hybrid Cryptography
A. Multi Biometric Image Fusion
Biometrics proposes the ability to rapidly capture real-time data
and provide authentication. The significant purposes for
biometric fusion are to improve system precision, competency,
applicability, and robustness. Some types of fusion have been
used successfully for years in large scale applications. Any two

ISSN: 2278-2397
21
biometric images like fingerprint image, iris, face or palm print
images can be taken for consideration [11] [12]. Both of the
images are taken in .png format and preferably in equal size. An
image fusion program is implemented to create a new layered
image out of these two biometric images. The output image will
have two layers one lying on the background and the other as
foreground.
Figure 3. Image Fusion of Fingerprint under Face Image
B. Fused Image Encryption using AES
The biometric images after fusion undergo encryption phase in
which Advanced Encryption Standard is used. AES is
considered to be one of the efficient and secure secret key
cryptographic algorithms for encrypting larger data
comparatively with other cryptographic algorithms. It is widely
used for encryption and authentic applications. In a scenario of
encryption, the following steps are carried out to encrypt a
128-bit block:
1. Derive the set of round keys from the cipher key.
2. Initialize the state array with the block data (plaintext).
3. Add the initial round key to the starting state array.
4. Perform nine rounds of state manipulation.
5. Perform the tenth and final round of state manipulation.
6. Copy the final state array out as the encrypted data
(cipher text).
This ensures the confidentiality of private data over the
network transmission of data. In authentication applications,
the sender encrypts the data using the secret key, which is to be
decrypted at the receiver end.
C. Encryption of AES Key using ECC
Since the AES Key is required to be sent to the receiver to
decrypt the fused image, and this key exchange mechanism
should ensure at most security. To attain this security, Elliptic
Curve Cryptography is used to encrypt the AES secret key.
Public key cryptographic techniques are proved for high
security environment using smaller key sizes[13]. Though,
various public key algorithms are outperforming each other,
Elliptic Curve Cryptography is even more better than other
public key cryptographic system. Hence, the proposed system
eventually uses ECC for encrypting AES Secret Key. ECC
uses the receiver’s public key for encryption, which is made
available in the public key ring. The encrypted AES Key along
with the encrypted image is sent to the receiver through
unprotected public media.
D. Decryption of AES Key
The receiver after receiving the encrypted key and the
encrypted image initially decrypts the secret key using ECC
private key. The AES Key is obtained through this and this key
is in return used to decrypt the fused image.
E. Decryption of Fused Image
Decryption of the fused image is decrypted using AES
decryption for which Secret key derived from the previous step
is used. The output is the fused image in which the fingerprint
is hidden behind the face image. This makes the system more
reliable, robust and authentic.
IV. CONCLUSION
In this paper, a system proposing a new hybrid cryptographic
system is proposed. Since, both symmetric and asymmetric
have their own advantages and drawbacks, this system
proposed made use of both the type of cryptographic
algorithms taking the advantages of each type. As implied AES
algorithm ensures the secrecy of the delicate images. And ECC
is used to securely exchange the AES key to the receiver. As
combined together, hybrid cryptography is expected to achieve
more security, robust and confidentiality. The system
proposed is limited to the following constraints. These
limitations can be overcome in future by identifying new
technologies and innovative modifications. Biometric images
should be scanned and stored as .png images so as to support
the image fusion code which is written; the two biometric
images, fingerprint and face images should be taken in equal
dimensions, in pixels for the images to be fused. The unequal
dimension images cannot be fused.
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