Biometrics Iris Scanning: A Literature Review


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The interest in Biometrics from both governments and industry has lead to the emergence of multiple Biometric technologies all with their own strengths and flaws. One currently at the forefront of Biometrics is iris scanning.

The process involved in the identification and verification of people using iris scanning is examined in this paper. The advantages and disadvantages associated with the utilisation of such a technology are also explored. A number of legal and ethical issues are highlighted. Iris scanning is looked at in comparison to other forms of Biometric technologies. Future work in the area of Biometrics is also considered in light of current developments.

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Biometrics Iris Scanning: A Literature Review

  1. 1. 1 Biometrics: Iris Scanning – A Literature Review [] BIOMETRICS: IRIS SCANNING A Literature Review WWW.OLIVIAMORAN.ME
  2. 2. 2 Biometrics: Iris Scanning – A Literature Review [] ABOUT THE AUTHOROlivia Moran is a training specialist who specialises in E-Learning instructional design and is acertified Moodle expert. She has been working as a trainer and course developer for 3 yearsdeveloping and delivery training courses for traditional classroom, blended learning and E-learning.Biometrics, Iris Scanning: A Literature Review was written as part of a group collaboration withBarry Feehily and Eric Nichols. WWW.OLIVIAMORAN.ME
  3. 3. 3 Biometrics: Iris Scanning – A Literature Review []AbstractThe interest in Biometrics from both governments and industry has lead to the emergence ofmultiple Biometric technologies all with their own strengths and flaws. One currently at theforefront of Biometrics is iris scanning. The process involved in the identification and verificationof people using iris scanning is examined in this paper. The advantages and disadvantagesassociated with the utilisation of such a technology are also explored. A number of legal andethical issues are highlighted. Iris scanning is looked at in comparison to other forms of Biometrictechnologies. Future work in the area of Biometrics is also considered in light of currentdevelopments.IntroductionOver the past number of years, identity theft has evolved into a billion dollar industry. Pinnumbers and passwords just do not cut it anymore. They are no match against shoulder surfingand card scanning. Developing new ways to protect information has become critical. Many haveturned to Biometrics making it one of the more popular alternatives. Biometric testing meansidentifying a person on the basis of physiological and behavioural characteristics. According toPrabhakar et al (2003) it enables “automatic personal recognition based on physiological orbehavioural characteristics”. The advances in technology in terms of processing power and cheapermemory have also fueled interest in this area.This article will examine Biometrics placing particular emphasis on remote iris scanning. It will takean in-depth look at how such technology functions. The advantages and disadvantages that areassociated with it will also be highlighted. Ethical and legal considerations are addressed. Acomparison of iris scanning is made with other kinds of Biometrics. Possible areas for futureresearch and development are proposed.How it WorksWith the current state of iris recognition technology, Kanda (2005) states “Up to 20 people can berecognised per minute if the scanning distance is within three metres and the subjects walkingspeed is less than one metre per second”. There are various algorithms for iris scanning. Plemmonset al (2004) describe eight different algorithms and write that they all share the same basic steps;obtain the iris image, extract the features and compare to a database for a match.Daugman (2004) algorithms are used in places such as British Telecom, US Sandia Labs, UK NationalPhysical Lab, NBTC, Panasonic, LG, Oki, EyeTicket, IBM SchipholGroup, Joh.Enschede, IriScan,Iridian, and Sensar. He reports that while using his algorithms, “all testing organizations havereported a false match rate of 0 in their tests, some of which involved millions of iris pairing”.Daugmans’ algorithms in the context of the above three steps will now be examined.
  4. 4. 4 Biometrics: Iris Scanning – A Literature Review []Step one involves obtaining the image. This step can only be successfully performed when peoplebeing scanned look in the general direction of the scanner without blinking. Obtaining the irisimage involves scanning the eye for the iris boundary, the pupil boundary, and the upper andlower eyelid boundaries, as shown in Figure 1. From these localisations the iris can be removedfrom the rest of the eye and encoded.Figure 1: Obtaining the iris image(Daugman 2004, p.1)Step two entails extracting the necessary features (i.e. encoding). It is done by scanning over theentire iris “with many wavelet sizes, frequencies, and orientations, to extract 2,048 bits” Daugman(2004). Each discrete item of extracted data contains two bits. Therefore there are 1,024 differentitems of information encoded. This includes not only the iris, but also masking items such aseyelashes that fall over the iris. As such, each eye is encoded with only 256 bytes.Step three involves comparing the collected data to a database for a match. This comparison isdone with a fractional Hamming Distance. Daugmans’ (2004) version of the Hamming Distance(HD) involves taking a scanned eye and applying an Exclusive OR to it and an item from thedatabase. The masking bits from the scanned eye and the eye in the database are the ANDed. Theyare then ANDed with the items that were applied an Exclusive OR. The result is made positive andthen is divided by positive ANDed masking bits to produce the Hamming distance, as shown in thefollowing equation by Daugman in Figure 2:Figure 2: Hamming Distance(Daugman 2004, p.4)When the HD is 0, then there is a perfect match between two irises. When the DH is 1, there is anabsolute mismatch. There must be a target for the comparator to resolve whether a match hasbeen made. Table 1 shows that a lower matching target results in less chance there will be a falsematch:Table 1: HD target result to false match (Daugman 2004, p.7)
  5. 5. 5 Biometrics: Iris Scanning – A Literature Review []If a system were only concerned with false matches, then a target at or near zero for positiveidentification would be desired. However, if a subject’s iris is more or less dilated, or if the subject’seye is slightly more closed or open, the mask will be different which will make the HD higher thanzero – even for the same iris. As such, a target HD of less than 0.30 on a world-wide scale would beadvised as this would ensure a positive match for the same iris while keeping the false matches atless than 1 in 13 billion.Advantages of Iris ScanningThere are a number of advantages associated with iris scanning. These include the following.Uniqueness of the IrisThe iris of each person has a unique nature. Unlike with DNA “An iris image is independent of anidentical genetic makeup” Horst (2006). Take for example, identical twins that come from thesame embryo. Both will share the same DNA, yet evidence from research into iris imaging showthat “even irises of identical twins are different” Jain et al (2000). Some people even go as far asto claim that “The iris is the most personally distinct feature of the human body” Kirsch (2006).Red Herring (2006) report, “The odds of being misidentified by an iris scan, assuming both eyes areused, are less than a trillion to one”.RobustnessIris scanning systems are more robust than other authentication methods such as face and voicerecognition. These systems can find it hard to cope with changes in the environment or theperson. For example, voice recognition may not work if the user is suffering from laryngitis or ifthere is excessive background noise. Irish scanning eliminates this problem.AccuracyAccuracy is of crucial importance. People will not trust a system that gives wrong results. “Aninaccurate system could falsely identify a traveler as a terrorist, or give a false sense of securitywhile failing to identify a real terrorist” (Bryant 2001). Recently in a report entitled NationalInstitute of Justice Research Report on Entry-Control Technologies, it has been claimed, “irispattern scanners are considered the most accurate of all Biometrics” (Jarvis 2006). The accuracy ofiris scans is higher than that of its contemporaries.Ease of UseRemote iris scanning systems are relatively simple to use. While the user has to undergo enrolmentit is short and easy to complete. The acquisition of the iris image does not involve any intrusiveprocedure. The user is not really required to interact with the system. The characteristics of the irisare captured by simply glancing into a digital camera for a fraction of a second. Ease of use isextremely important when it comes to gaining acceptance. If people feel that controls are tooannoying or time consuming they will simple override them. It is this ease of use that has proven ahuge success in US airports for both access control as well as passenger ticketing. It has also beensuccessful in use for ticketing at sporting events.
  6. 6. 6 Biometrics: Iris Scanning – A Literature Review []SecurityRemote iris scanning is more secure than other methods of identification such as pins andpasswords. These can be guessed and there exists the danger that someone could ‘shoulder surf’you while you type it in. These identification methods also run the risk of been stolen should theybe written down and fall into the wrong hands. Fooling an iris scanning system is almostimpossible as it is “extremely difficult to surgically tamper iris texture information and it is easy todetect artificial irises” Jain et al (2000). No other biometric technology can rival the combinedattributes of mathematical certainty.SpeedIris recognition is widely accepted as the fastest form of biometric testing and is suitable for usewhere a large number of people are involved. Iris Scanning has been successfully deployed atseventeen air, land and seaports in the United Arab Emirates (UAE). Border officials have scannedthe irises of 900,000 people whose visas have expired or who have been asked to leave the country.Using those scans to screen arrivals has uncovered 650,000 illegal aliens trying to re-enter the UAEusing false passports. At Amsterdam Schiphol Airport, frequent travelers have been using iris scansto speed up entry and immigration checks since 2001. There is no question that iris scanning is thebest choice where huge volumes of people need to be processed quickly.Disadvantage of Iris ScanningThere are multiple weaknesses associated with iris scanning which need to be improved upon inthe future. These include the following.CostsOne of the main reasons for slow adoption of Iris Scanning is the high cost currently associatedwith the installation and maintenance of such technology. It is expected however, as the industrymatures and use of iris scanning becomes more wide spread, that costs will be reducedsignificantly. As outlined by Torbet et al (1995), “Many biometric devices could be integrated withthe existing system, with the exception of the input sensor. This will reduce the cost and makewide-scale adoption more likely”.AcceptabilityUsers generally don’t like the unfamiliar. People are slow to adopt new technologies especiallywhen they see them as interfering with their privacy and confidentially. In order for iris scanningto be acceptable its operation must be perceived by its potential users to be “at least as well, orbetter, than any currently available alternative” Torbet et al (1995).Fraudulent UseAlthough the risk is relatively low the data collected during the iris scans could be used for fraud.“Such fraud can occur at the enrolment stage as well as well as the verification stage” (Bennett2000). During the enrolment phase someone may be able to set up a false template. Fraud canalso take place during the verification or identification stage. When the system scans the users iris
  7. 7. 7 Biometrics: Iris Scanning – A Literature Review []the resulting data must be compared against the relevant template. This template is usually storedin a central database. Therefore, data must be transmitted at this point. If this transmission is notsecure it is possible for others to intercept the information. They can then use it for whateverpurpose they wish.SecurityNo system is one hundred percent accurate and that includes Biometrics. Although iris scanningreduces the risks, there is always room for error. From the research conducted it is highlighted thatthere is a False Rejection Rate, where the system rejects the right person and the False AcceptanceRate, where the wrong person is accepted. The levels of these errors however are deemed to bewell under the acceptable level.Industry StandardsAs outlined by Emory (2002) “The development and acceptance of a primary standard is critical forthe growth and applicability of the biometrics industry”. While industry standards do exist, theydo leave room for improvement and are few and far between. The bigger more powerfulcompanies such as Microsoft refuse to conform in order to build a better product and they createtheir own set of standards. The adoption of global standards would limit and minimise the abuseof data collected. However, the adoption of standards is voluntary and not legally binding.Legal ConsiderationsThe rapid progression of the use of Biometrics and Iris Scanning has raised concerns from a legalpoint of view, especially the legislation concerning privacy and the protection of data. From thisarticle it is clear that all Biometrics involves working with and processing data. As a resultBiometrics must comply with legal requirements that are currently in place. Take for example ‘TheData Protection Act (1998)’ in Ireland. According to this act personal data should be collected for aspecific purpose and should be adequate, relevant and not excessive for the purpose for which it iscollected and processed. In addition it must be accurate and up to date. Appropriate securitymeasures must be in place to protect it. If a company is found to be in breech of the requirementsof this act they can be prosecuted.Ethical ConsiderationsDisabled UsersAdvocates of iris scanning market it as being the only system needed for authentication. This isfine for most but what about the small group of people who do not have an iris? Obviously thesepeople cannot undergo iris scans. The exclusion of users with disabilities is not ethical nor is itlegal. We claim to be an inclusive modern society and yet little consideration is given to thisgroup. Using a mulitmodal system could overcome this limitation. Users could carry a smart card,which would contain information about their lack of iris. The system could then permit anoverride for this individual. Authentication could be done by some other means such as
  8. 8. 8 Biometrics: Iris Scanning – A Literature Review []fingerprint or facial recognition. Such a multimodal system “offers higher and more consistentperformance levels” (Bennett 2000).Privacy ConcernsOne of the major concerns associated with the use of any Biometric system is privacy. There is athreat to privacy and civil liberties because of potential for a wide range of people to cross-reference information. People wish to keep their confidential information exactly that,confidential. If we give all our information to a bank what is stopping them from selling thisinformation to a third party such as a marketing agency. Even worse what could the “Potentialimpact that government might use of these technologies might have on personal freedom ... Thegovernment could use some unforeseen technological advances to compile biometric records forthe real-time tracking of individuals” Wayman (2000). Currently such technologies are utilised inmany countries to find and track criminals. This could however be extended to cover the wider lawabiding population.Up until now fingerprinting has been collected mainly for the use of law enforcement e.g.criminals and this is a very sensitive issue for many people. However, it must be acknowledged thatiris scanning reduces the quantity of personal information that needs to be created and stored.Iris Scanning Versus Other Forms ofBiometric TestingRetina recognition relies on the retina’s blood vessel pattern. Unlike iris scanning, this technologyis personally invasive and requires skilled operators and time. Facial recognition examinescharacteristics such as eyes, nose and mouth positioning taking into account the distances betweenthem. To date attempts to get computers to recognise faces have had only limited success. Thechallenge here is producing hardware that will map the features of the face reliably andaccurately. Voice Recognition based on vocal characteristics is not intrusive, however, it is sensitiveto background noise and vulnerable to attack.Today the fingerprinting is probably the most common form of Biometric technology used. Thisinvolves matching minute features such as ridge and endings. While it is a widely accepted form ofBiometric testing it also has its drawbacks. The success of this process is highly sensitive to imagequality. Failure of this system can result from dirt and scars on the fingers along with poor fingerpositioning. According to Matsumoto (2002) “Biometric samples or even templates may beconstructed, for instance artificial fingers may be used by attackers”.As a result it is quite evident Iris Scanning offers advantages over alternative biometric techniques.
  9. 9. 9 Biometrics: Iris Scanning – A Literature Review []Future WorkWhile iris scanning has been successful in providing a false match rate of zero, it has a weaknessthat must be addressed. The system needs direct visual contact with every subjects’ iris for it tooperate. A person turning his or her head while talking to another could be a common occurrencein a system that scans many people at once. People could also take advantage of this weakness.An example is a locked door that needs iris identification in order for it to unlock. A person withauthority to pass could unlock the door with an iris scan. Before the door re-locks, people withoutauthority to pass through the door could close their eyes and also pass through before the door isre-locked. The system would not be aware that an unauthorised person had breeched the security.An additional security system such as a guard at the scanner would therefore be required. This is aproblem inherent in iris scanning.In order to implement a better system technology would have to be utilised that could allow forthe remote identification of individuals. Such a system would not depend upon actions from thoseindividuals. Brainwave biometrics would provide this solution. Lawson (2002) notes that people“cannot alter what is referred to as their baseline brainwave pattern”. Every person’s baselinebrainwave pattern is unique. From birth until death people broadcast unchanging and uniquewaves from their brain. Technology that could receive and decode these waves would provide afoolproof means of personal identification.Future work in this area is needed from various fields. For instance, hardware would be neededthat is capable of receiving baseline brainwaves. The issue of storing individual’s brainwaves ondatabases will need to be addressed. Algorithms would have to be developed to convert thesewaves into a binary format. A way to compare the brainwaves so that a match can be immediatelyfound will also need to be implemented. There is plenty of future work to be done in this area.Once such work is completed the best possible system of personal identification will have beenavailable for use.ConclusionIn this document the area of Biometrics was critically examined focusing on iris scanning. The wayin which the entire iris scanning process works was illustrated. The benefits and shortcomings ofthis particularly technology were addressed as well as the legal and ethical problems arising fromthe use of such technology. Iris scanning was considered in relation to other technologies andcomparisons were made. Lastly, areas for future research and development were put forward.Two important issues globally affecting the world today are identification and authentication ofan individual. Identification says who you are and authentication specifies that you are who yousay you are. From the research conducted it is quite evident that the use of Biometrics and irisscanning for the above purpose is fast gaining worldwide recognition.
  10. 10. 10 Biometrics: Iris Scanning – A Literature Review []It is clear to see that Iris Scanning is a highly accurate and speedy form of Biometric Testing and issuitable for use in many different situations especially where speed is essential e.g. airports.However, the one major drawback at this time is its high implementation costs. With thedevelopment of a more cost-effective system, it is anticipated that iris scanning will be used morewide spread and it will gain a higher level of recognition in the future.Biometric Technology also raises privacy-related concerns. Biometric systems must comply with theprinciples of data protection legislation, since they create and process data, however, as BiometricTechnology is been widely implemented across the world, it is anticipated that countries willupdate their laws to facilitate surveillance of this new technology.Overall, especially after the tragic events of the attacks of the 11th of September 2001 and thecurrent fight against terrorism, it is likely that Biometrics and iris scanning will increasingly becomepart of everyone’s life but like all other data collection and processing systems, it must be handledwith care. It will only be useful if the processes surrounding it are safe and secure.