**2.2. Biometric system**

It is an essential pattern recognition system that uses the human characteristics in order to identify the person divided into unimodal system when using single trait and one that uses more than single traits called multi-biometric [14]; when developing a reliable biometric system, there are some concerns that need to be analyzed and balanced as needed [7]:


Unimodal systems suffer from low-resolution data due to the person or the sensor, and this can lead to high failure to enroll rate, lacking people coverage area, and low recognition rate because cooperation with the user is needed to collect the data. So it is almost difficult to get very high recognition rates using unimodal system [14]; to improve the recognition rate, we need to acquire more than one trait from the same sensor or multiple sensors, but while increasing the recognition rate, the complexity and processing, which is time-consuming, increase.

Some problems associated with the unimodal biometric systems can be overcome by the use of the multi-biometric systems that combine the information obtained from multiple sources [15]. Still, such a system has two major limitations: first, the overall cost to construct the system can be prohibitive due to the need for more high-quality sensors, large storage capacity, and computational requirements. Second, the system requires a longer time for verification, hence causing inconvenience to the users [10]. However, soft biometrics are the solution to decrease the cost by using the same sensor [10]. The main steps for a biometric system are as follow [7, 16] as shown in **Figure 3**:

• Can be used when there is a difficulty to collect a primary biometric trait or the collected data is not clear due to the sensor error or data collected from a distance with no coopera-

• Acceptable: collecting data for identification don't need cooperation between the person

• Soft facial biometrics are not expensive to compute since they can be acquired at the same

• Enrolling person needs no cooperation and taken at distance even training of the system

• Soft biometric bridges the gap between machine and human since they have a semantic

• Soft biometrics don't rise a privacy concern about collecting and saving data because they

• Filtering and indexing the large database to limit the number of searched data according to the connected person characteristics [13], for example, we can restrict the search for female

It is an essential pattern recognition system that uses the human characteristics in order to identify the person divided into unimodal system when using single trait and one that uses more than single traits called multi-biometric [14]; when developing a reliable biometric sys-

• Harmless to the users, as reported a research company put a SIM card under the skin for

• Performance, which means the highest recognition rate and system speed, while tolerance

• Circumvention means how easily your system can be overcome or bypassed using fake

Unimodal systems suffer from low-resolution data due to the person or the sensor, and this can lead to high failure to enroll rate, lacking people coverage area, and low recognition rate because cooperation with the user is needed to collect the data. So it is almost difficult to get very high recognition rates using unimodal system [14]; to improve the recognition rate, we need to acquire more than one trait from the same sensor or multiple sensors, but while increasing the recognition rate, the complexity and processing, which is time-consuming, increase.

tem, there are some concerns that need to be analyzed and balanced as needed [7]:

the environmental factors affecting the system, stable and time invariant.

• Acceptability, are the people ready to use their biometric trait?

meaning and can be understood by the human as old and short African male.

provide ancillary description and are not fully distinctive as old and short male.

tion with the user.

40 Machine Learning and Biometrics

is done offline.

gender.

**2.2. Biometric system**

authentication.

techniques.

• Accessible, easy to use.

and the sensor and available.

time during primary face biometric collection.


**Figure 3.** Biometric system enrollment and identification diagram.
