Person identification and authentication is the biggest challenge in our society. Identity may be considered as a public information, but an authentication must necessarily be private- a secret that is known only to the user. Moreover, the authentication must be a conscious process that requires active participation by a user, but not necessarily an identity verification (Agrawal et al., 2017). Generally person uses User ID (Login ID), cryptographic public keys, email ids, ATM or smart cards; some common authentication credentials are passwords (including OTPs), PINs, and cryptographic private keys.

Now Government of India have launched a World's largest database based a digital project known as “Aadhaar”. It provides a 12 digit unique code to each person which shows the uniqueness of a person in the world. Aadhar is the best example of multimodal biometric system which contains the demographic information with multiple biometric traits such as face, iris, fingers, and thumbs. Most of the government services and resources are linked to Aadhaar number of a person for authenticity and security.

A person identified as an individual in a group by physiological or biological characteristics, such as face, ear, fingerprint, iris, thumb, voice, signature and keystroke is known as Biometrics. These features are unique to each individual and remain unaltered during lifetime (Mahesh & Swamy, 2011). Technically we define Biometrics as a body measurement and calculations and the metrics are related to human uniqueness (Biometrics, (n.d.)). Biometric system is designed to make decisions against the persons as it is accepted/ authorized and rejected/ impostors.

Biometric system is divided into two major processes namely Training and Testing.

In training process, the biometric modality is captured and converted into suitable template. This process is performed as:

• Input image or signal is captured or acquired.
• The signal is pre-processed to remove noise or some similar signal; or image resizing, reformatting takes place.
• Feature extraction is performed.
• Features are transformed into suitable templates and these are stored in template database.

The testing process is performed at the time of matching, which is similar to training method. The input is captured and it is subjected to:

• Pre-processing.
• Feature extraction.
• Template conversion.

The template is matched against the templates already present in the template databases (Jamdar & Boke, 2017).

Result recognition based on a single biometric trait may not be sufficiently robust and it has a limited ability to overcome spoofing (Barde et al., 2012).

Some of the challenges commonly encountered in implementation of biometric systems are given as follows.

• Noise: A biometric data captured through an image acquisition system or sensor may be influenced by noise signal added due to sensor itself. This may be due to imperfect acquisition conditions. Other factors that could contribute noise are subtle variations in the biometric itself such as a fingerprint image with a scar or a voice sample altered by cold. Noisy data could also result from defective or improperly maintained sensors such as accumulation of dirt on a fingerprint sensor or unfavorable ambient conditions, for example, poor illumination.
• Intra-class variations: These variations are generally caused by a user who is incorrectly interacting with the sensor, i.e. incorrect facial pose, or when the characteristics of a sensor are modified during authentication.
• Non-universality: The biometric system may not be able to acquire meaningful biometric data from a subset of users. A fingerprint biometric system may extract incorrect minutiae features from the fingerprints of certain individuals, due to the poor quality of the ridges.
• Spoof attacks: This type of attack is relevant when behavioral traits such as signature or voice are used. However, physical traits such as fingerprints are also susceptible to spoof attacks.

The biometrics using single trait or characteristic is very simple and easy to use. However, these biometric systems have the following major drawbacks:

• The lack of universality of some characteristics.
• Noisy signals captured through the sensors due to the incorrect usage and due to the environmental conditions, such as humidity, dirt, dust, etc.
• The discrimination of biometric systems due to a high in-class and low inter-class variability.
• The recognition performances of unimodal systems are limited to certain level.
• Error rates are sometimes unacceptable.
• The lack of permanence and variability in biometric characteristics.
• The possibility of fraud through voluntarily or involuntarily cloning.
• If there are problems with the trait being used; no alternative could save the biometric system (Ross & Jain, 2003).

Figure 1 shows the working of biometric system.

Figure 1. Biometric System

The term “Multimodal” is used to combine two or more different biometric traits of a person like face, ear, iris, finger, thumb, voice, and signature sensed by different sensors. A multimodal biometric system integrates multiple source of information obtained from different biometric sources (Barde et al., 2014). The enrollment is a very important process involved in biometrics and is shown in Figure 2 and the steps of biometric trait enrolment are as follows.

Figure 2. Enrollment Process of Biometrics

• The biometric data or input is captured using suitable acquisition system or sensor.
• The modality is stored inside the biometric database.
• Features are extracted from the traits and converted into suitable transformations called as biometric templates.

Multiple sources of biometric information are combined for overcoming some of the limitations mentioned in unimodal biometric system and the multimodal biometrics is shown in Figure 3, where some modalities, namely face, iris, thumb, and fingerprint of same person are captured and subjected to training process of biometrics. These modalities could be combined at various levels and it is easy to take decision at matching score level, where the training data of relevant person is matched or not. After matching the pieces of evidence are combined. Multiple classifier result scores are combined to generate a single scalar score. The match scores generated by the face, iris, thumb, and fingerprint modalities of a user may be combined using a simple sum rule method in order to obtain a new match score, which is then used to make the final decision. The result proves the authenticity of person.

Figure 3. Multimodal Biometric System

Indian Government launches a digital innovative project under the scheme 'UIDAI' (Unique Identification Authority of India) by the UPA (United Progressive Alliance) government in year 2009. Aadhaar is one of the significant projects to bring the universal trend. The main purpose of Aadhaar is centralization of various egovernance functionalities and to make sure the utilization of information in a best possible manner. Aadhaar card is a combination of demography and multimodalities, which provides the unique ID to every person to help identify the person individually. Aadhaar card overcomes the limitation of biometric system and enhances the features of multimodal biometrics system.

The main aim of Aadhaar is to provide authentication of uniquenes of a person and for this, digital privacy and security are very much required.

Aadhaar card is a combination of demographic feature and multi-biometrics. Traits such as Date of Birth, Sex, address of the citizen, and biometric features, such as photograph, fingerprints and iris (eye) along with a 12-digit unique identity number for every citizen are included.

In Digital India concept, Aadhaar helps to identify a person anywhere in the World, provide surveillance, tracking, or profiling of people using the centralized database.

A person’s data is completely sheltered from manual inspection or unauthorized person by the UIDAI or the Government. All transactions, investigations, and analytics can be carried out in a safe way. Figure 4 shows a model Aadhaar card containing the Unique ID of a person.

Figure 4. Image of Aadhar Card Contain Unique ID

The advantages of Aadhaar card are in various fields. Now the Government of India has been linking the Aadhaar card with various government schemes, such as for cooking gas subsidies, house allotments, school scholarships, passports, e-lockers (eg. Digilocker), bank accounts, provident funds account, insurance policies, and others. Aadhaar card was made mandatory for authentication purposes like ATM card, salary payment, pension schemes, school enrolment, train booking, driving license, and to get a mobile sim (Legal Bites, 2017).

Indian Railways is the World's largest transportation media. IRCTC is going to make Aadhaar mandatory for the online ticket booking system. Aadhaar Number would be required for one-time registration in the IRCTC ticketing websites an OTP (One Time Password) sent to his/her registered mobile number. Aadhaar card can help a lot to improve the existing railway reservation system (The Hindu, n.d.).

According to Indian Express, there are over 2,15,039 number of ATMs (Automated Teller Machine) till the end of June 2016 in India. Now every Bank is linked with Aadhaar to provide security. ATM transaction is possible through the password which is changed only by the user (Pandey, 2017).

Now Electronic Voting Machine (EVM) is used for voting in India. Aadhaar based model has suggested to eliminate the drawbacks of existing voting system (Gupta et al., 2013).

“Aadhaar e-KYC (Electronic-Know Your Customer) eService” automatically fills with the details of Aadhaar card. The main objective to implement this service is that it offers biometric based validation which eliminates all the extra machines required to record biometric details of a person (Bhoyar et al., 2016).

E-health care was introduced in India using Internet Technology. Apollo Healthcare, ISRO, and CSIR provide Ehealthcare services in India. To overcome the possible threats due to insiders, Aadhaar based E-health system was suggested.

To make effectiveness, the Municipal Corporation uses Aadhaar card for registration and gets a message from the website and after the problem is solved by municipal corporation, the status has changed. Basic idea behind that is to make a direct communication between municipal corporation and citizens.

PDS (Public Distribution System) was implemented in India in 1965 for the poor people who can have the food delivered at a low cost or free of cost. The entire country was divided into two parts, APL (Above Poverty Line) and BPL (Below Poverty Line). Now, only BPL citizens are only allowed to have an access to the PDS at low or free of cost (Ramakumar, 2011). Recently, the government has linked Aadhaar card with the PDS system to overcome the frauds.

PFRDA (Pension Fund Regulatory and Development Authority) was established in 2003 to develop and regulate pension sectors in India. In 2004, NPS (National Pension Scheme) was established to provide pension to citizens all over India. Recently, NPS has been restructured and the pensioners are asked to link Aadhaar number with the pension scheme. The main objective of linking Aadhaar is to prevent the delaying of the payments every month (Government of India, 2012).

PMJDY (Pradhan Mantri Jan Dhan Yojana) is a National Mission for financial inclusion in which it allows a citizen to open a savings account with no minimum balance, i.e. zero balance account. Recently, Aadhaar has been linked with PMJDY. Therefore, a user can open an account with an Aadhaar card as a proof, and can avail the government welfare schemes’ benefits plus to avoid the misuse of the overdraft facility given to the user (Kamat, 2014).

Last decade, person identification and authentication was a big challenge because there were no specific method to identify a person. They generally used passwords, key, or PIN (personal identification number), which has many drawbacks, such as; the password may be forgotten or hacked; PIN numbers may be stolen or cracked by unauthorized user; or cards may be lost, stolen, used together, and easily duplicated. Biometric had found the solution of this problem and multimodal biometric overcame the limitations of biometric and has improved security. Aadhaar card, one of the best ideas provided by Government is a combination of demography and multimodal biometrics used in many government services and applications prove more secure authentication and identification of persons.