Editing Biometrics (section)

==Biometric functionality==
Many different aspects of human physiology, chemistry or behavior can be used for biometric authentication. The selection of a particular biometric for use in a specific application involves a weighting of several factors. Jain ''et al.'' (1999)<ref name=Jain2>{{Cite book
 | title = Biometrics: Personal Identification in Networked Society
 | publisher = Kluwer Academic Publications
 | editor-last = Jain
 | editor-first = A. K.
 | editor2-last = Bolle
 | editor2-first = R.
 | editor3-last = Pankanti
 | editor3-first = S.
 | year = 1999
 | isbn = 978-0-7923-8345-1
}}</ref> identified seven such factors to be used when assessing the suitability of any trait for use in biometric authentication. Biometric authentication is based upon biometric recognition which is an advanced method of recognising biological and behavioural characteristics of an Individual.  
* Universality means that every person using a system should possess the trait.
*[[Uniqueness]] means the trait should be sufficiently different for individuals in the relevant population such that they can be distinguished from one another.
* Permanence relates to the manner in which a trait varies over time. More specifically, a trait with ''good'' permanence will be reasonably invariant over time with respect to the specific matching [[algorithm]].
* Measurability (collectability) relates to the ease of acquisition or measurement of the trait. In addition, acquired data should be in a form that permits subsequent processing and extraction of the relevant feature sets. 
* Performance relates to the accuracy, speed, and robustness of technology used (see [[#Performance|performance]] section for more details). 
* Acceptability relates to how well individuals in the relevant population accept the technology such that they are willing to have their biometric trait captured and assessed. 
* Circumvention relates to the ease with which a trait might be imitated using an artifact or substitute.

Proper biometric use is very application dependent. Certain biometrics will be better than others based on the required levels of convenience and security.<ref>{{Cite journal|url = http://www.appliedclinicaltrialsonline.com/biometrics-comes-age|title = Biometrics comes of age: despite accuracy and security concerns, biometrics are gaining in popularity|last = Bleicher|first = Paul|date = 2005|journal = Applied Clinical Trials| series=Applied Clinical Trials-12-01-2005 |access-date = 6 December 2019}}</ref> No single biometric will meet all the requirements of every possible application.<ref name=Jain2 />

[[File:Biometric system diagram.png|thumb|upright=1.5]]The block diagram illustrates the two basic modes of a biometric system.<ref name="Jain1">{{Cite book|last1=Jain|first1=Anil K.|title=Handbook of Biometrics|last2=Ross|first2=Arun|publisher=Springer|year=2008|isbn=978-0-387-71040-2|editor-last=Jain|editor-first=AK|pages=1–22|chapter=Introduction to Biometrics|editor2-last=Flynn|editor3-last=Ross|editor3-first=A|chapter-url=https://www.springer.com/computer/image+processing/book/978-1-4419-4375-0|archive-url=https://web.archive.org/web/20110309042959/http://www.springer.com/computer/image+processing/book/978-1-4419-4375-0|archive-date=9 March 2011|url-status=live}}{{payment required}}</ref> First, in [[Authentication|verification]] (or authentication) mode the system performs a one-to-one comparison of a captured biometric with a specific template stored in a biometric database in order to verify the individual is the person they claim to be. Three steps are involved in the verification of a person.<ref name=Choubisa>{{cite journal |last1=Sahoo |first1=Soyuj Kumar |last2=Choubisa |first2=Tarun |last3=Prasanna |first3=SR Mahadeva |title=Multimodal Biometric Person Authentication : A Review |journal=IETE Technical Review |date=1 January 2012 |volume=29 |issue=1 |pages=54–75 |doi=10.4103/0256-4602.93139 |doi-broken-date=1 November 2024 |doi-access=free|s2cid=62699150 }}</ref> In the first step, reference models for all the users are generated and stored in the model database. In the second step, some samples are matched with reference models to generate the genuine and impostor scores and calculate the threshold. The third step is the testing step. This process may use a [[smart card]], username, or ID number (e.g. [[Personal identification number|PIN]]) to indicate which template should be used for comparison.<ref group="note">Systems can be designed to use a template stored on media like an [[Biometric passport|e-Passport]] or [[smart card]], rather than a remote database.</ref> ''Positive recognition'' is a common use of the verification mode, "where the aim is to prevent multiple people from using the same identity".<ref name=Jain1 />
[[File:Biometric Island, Gdansk University of Technology 2021.jpg|thumb|''Biometric Island'' examining facial image 2D and 3D, voice timbre, and [[signature recognition|verifying handwritten signature]]|right]]

Second, in identification mode the system performs a one-to-many comparison against a biometric database in an attempt to establish the identity of an unknown individual. The system will succeed in identifying the individual if the comparison of the biometric sample to a template in the [[database]] falls within a previously set threshold. Identification mode can be used either for ''positive recognition'' (so that the user does not have to provide any information about the template to be used) or for ''negative recognition'' of the person "where the system establishes whether the person is who she (implicitly or explicitly) denies to be".<ref name=Jain1 /> The latter function can only be achieved through biometrics since other methods of personal recognition, such as [[passwords]], PINs, or keys, are ineffective.

The first time an individual uses a biometric system is called ''enrollment''. During enrollment, biometric information from an individual is captured and stored. In subsequent uses, biometric information is detected and compared with the information stored at the time of enrollment. Note that it is crucial that storage and retrieval of such systems themselves be secure if the biometric system is to be robust. The first block (sensor) is the interface between the real world and the system; it has to acquire all the necessary data. Most of the times it is an image acquisition system, but it can change according to the characteristics desired. The second block performs all the necessary pre-processing: it has to remove [[artifact (error)|artifact]]s from the sensor, to enhance the input (e.g. removing background noise), to use some kind of [[normalization (image processing)|normalization]], etc. In the third block, necessary features are extracted. This step is an important step as the correct features need to be extracted in an optimal way. A vector of numbers or an image with particular properties is used to create a ''template''. A template is a synthesis of the relevant characteristics extracted from the source. Elements of the biometric measurement that are not used in the comparison algorithm are discarded in the template to reduce the file size and to protect the identity of the enrollee.<ref>{{Cite web|url=https://ievoreader.com/how-biometric-data-is-stored/|title=How Biometric Data is Stored|date=2018-12-10|website=ievo Ltd|language=en-GB|access-date=2020-02-22}}</ref> However, depending on the scope of the biometric system, original biometric image sources may be retained, such as the PIV-cards used in the Federal Information Processing Standard Personal Identity Verification (PIV) of Federal Employees and Contractors (FIPS 201).<ref>{{Cite journal|last1=Grother|first1=Patrick|last2=Salamon|first2=Wayne|last3=Chandramouli|first3=Ramaswamy|date=July 2013|title=Biometric Specifications for Personal Identity Verification|url=https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-76-2.pdf|pages=NIST SP 800–76–2|doi=10.6028/nist.sp.800-76-2|doi-access=free}}</ref>

During the enrollment phase, the template is simply stored somewhere (on a card or within a database or both). During the matching phase, the obtained template is passed to a matcher that compares it with other existing templates, estimating the distance between them using any algorithm (e.g. [[Hamming distance]]). The matching program will analyze the template with the input. This will then be output for a specified use or purpose (e.g. entrance in a restricted area), though it is a fear that the use of biometric data may face mission creep.<ref>{{Cite web|url=https://www.federalregister.gov/documents/2018/08/09/2018-17079/agency-information-collection-activities-biometric-identity|title=Agency Information Collection Activities: Biometric Identity|date=2018-08-09|website=Federal Register|access-date=2020-02-22}}</ref><ref>{{Cite web|url=https://www.dhs.gov/sites/default/files/publications/Center%20for%20Democracy%20%20Technology%20Comment%20DHS-2019-0001%20%28003%29.pdf|title=Re: DHS 2019-00001, DHS Data Privacy and Integrity Advisory Council|last=Taylor|first=Sandra|date=25 February 2019|website=Department of Homeland Security|access-date=20 February 2020}}</ref>
Selection of biometrics in any practical application depending upon the characteristic measurements and user requirements.<ref name=Choubisa /> In selecting a particular biometric, factors to consider include, performance, social acceptability, ease of circumvention and/or spoofing, robustness, population coverage, size of equipment needed and [[identity theft]] deterrence. The selection of a biometric is based on user requirements and considers sensor and device availability, computational time and reliability, cost, sensor size, and power consumption.