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Accessibility of biometrics: Dimensioning the challenges and opportunities

John Gill

There is increasing interest in systems which help confirm a person's identity. From the government's perspective this is, in part, motivated by security considerations at a time of international terrorism. At the individual level there is concern over identity theft leading to financial loss. Identity fraud is estimated to cost the UK over a billion pounds each year split equally between the public and private sectors.

In the next few years, biometric systems will be more widely used by the general public for applications such as passports. For some people, biometric systems are likely to be much easier to use than the conventional identification systems, but it is important that significant sections of the community are not unnecessarily excluded from using such systems. Table 1 gives an indication of the order of magnitude of the number of people with special needs.

Table 1: People with special needs in the UK

Children (<16 years) 20%
Older people (>65 years) 15%
Disabled (with respect to using ICT) 10%
Primary language not English 5%
Left-handed 10%

There is no published data on the number of people with disabilities, but the numbers of people estimated to have problems using information and communication technology systems may be indicative.

Table 2: User with problems using ICT

Wheelchair users 0.4%
Cannot walk without an aid 5%
Reduced strength 2.8%
Reduced co-ordination 1.4%
Speech impaired 0.25%
Language impaired 0.6%
Dyslexic 1%
Intellectually impaired 3%
Deaf 0.1%
Hard of hearing 6%
Blind 0.4%
Low vision 1.5%

Within these groups there are considerable variations from one individual to the next. For instance people with low vision includes those with:

(a) Macular degeneration

Macular degeneration accounts for about half of all registerable blindness in the UK; it is particularly common among the older population. Typically it results in the loss of central vision. This group often benefits from larger than normal print.

How a TV would  look to someone with macular degeneration

(b) Cataracts

A cataract is an opaqueness of the lens at the front of the eye. It has similarities to driving a car with a dirty windscreen; if the sun is in your eyes, it is difficult to see anything, but with the sun behind you there are relatively few problems. Fortunately cataracts can usually be operated on successfully, with the lens being replaced by a plastic lens.

How a TV would to someone with cataracts

(c) Diabetic retinopathy

Haemorrhages occur on the retina at the back of the eye. One effect of diabetes tends to be a very poor sense of touch; therefore few people with diabetic retinopathy can read braille.

How a TV would look to someone with diabetic retinopathy

(d) Tunnel vision

Tunnel vision can be associated with some forms of retinitis pigmentosa or a late stage of glaucoma. Retinitis pigmentosa (RP) is the name for a group of conditions which are genetic and result in night blindness. Glaucoma is from increased pressure in the eye; if detected early enough, then it can be treated by taking pills.

How a TV would look to someone with tunnel vision

In addition total colour blindness affects about 0.0025% of the population. However about 8% of males and 0.5% of females have problems distinguishing red and green.

The ageing process affects vision. In a sixty year old only about one third of the light reaches their retina compared to when they were twenty. There is also a decline in visual accommodation (the ability of the eye to change focal distance) coupled with a deterioration in the speed of adapting to changes in illumination. In addition many older people have a combination of impairments. Also multi-tasking becomes less easy. The effect of all these factors is that many older people may have problems in using a biometric terminal at the same speed as their younger counterparts.

There are three elements of a person's identity:

  1. Things which you 'are' i.e. your biometric identity. These are attributes that are unique to an individual (e.g. fingerprints).
  2. Things are given to you i.e. your attributed identity. These include full name, date and place of birth.
  3. Things which happen to you during your life, i.e. your biographical identity. This includes educational qualifications, electoral register entries, and history of interaction with organisations such as banks.

Biometrics permits the automatic identification of an individual based on his or her distinguishing physiological and/or behavioural characteristics. Biometric identification involves comparing with a database of templates to find out who you are, but biometric verification is where the template is compared to the one supplied with your claimed identity. Some biometric systems cannot do identification but can only verify the claimed identity of a person.

Table 3: Common biometrics

Hand geometry
Dynamic signature
Vein geometry
Facial recognition
Iris recognition

For the user, it should be easy and comfortable to use the system. Many users would prefer methods which do not require physical contact between the individual and the device. Consumers need confidence that the system will reliably correctly identify them while not permitting other users access; no current biometric system achieves 100% success in both these aspects.

Two different systems need to be designed so that they can be used comfortably by as many people as is reasonably possible. Firstly the system which captures the biometric. This will normally be manned by experienced personnel who should have received some training in working with people with disabilities.

Secondly there are the biometric readers which may be unmanned or have limited supervision. It is essential that these terminals have a consistent user interface. They should incorporate standard icons, symbols and pictograms to help the user operate the terminal. This will be particularly important for applications such as passports where there is a significant probability that the user is not familiar with the local language.

It would also be desirable for the user to be able to personalise the user interface. This can be done by pressing a button or selecting from a menu, but this is time consuming for anything other a simple change. Alternatively the user's preferences could be stored on a central database or on the user's card or smart media. There is a European standard (EN 1332-4) for how to code this information.

Facial recognition

Facial recognition can have an unacceptable level of either false positives or false negatives. It is technically best used to say "is this the same person" rather than "who is this person". Thus it is an appropriate technology when used with a secure token such as a smart card. From the users perspective it's non-intrusive nature is a major advantage and users are likely to accept such a system if it can provide a decision quickly, and is seen to be protecting their interests.

In passport applications, a false rejection will only result in a referral to an immigration officer who can handle problems such as changes in facial appearance.

Fingerprint systems

Fingerprint systems are good for the low number of false acceptances, but can be problematic for those with damaged fingers or with prosthetic hands. Some users will associate fingerprints with criminal investigations, so may be reluctant to use the system.

Iris recognition

Iris recognition is a secure system, but the user may have to position their eye in relation to a camera. This can give problems for users who are very tall, very short, or in a wheelchair. There are obvious problems for users who are blind or have a visual prosthesis. In addition some ethnic and religious groups may consider such a system unacceptable.


The biometric information can be stored in a central database or on a smart card. Users are likely to prefer the information to be stored on their card rather than on a remote database. However, it is easier to regularly update the database with revised biometric data as the user's characteristics change.

Users should have the facility to choose an alternative verification system even if it is a PIN. However this choice may be subject to regulatory or legal requirements imposed on the service provider. The user should be advised if the alternative is less secure, but the decision to use an alternative system should be left to the user.

The obvious advantage of biometric systems is that the user no longer has to remember PINs (personal identification numbers) and keep this number secret. So many people with a cognitive impairment will find most biometric systems much easier to use and provide a greater level of security.

However there are a number of unknown effects such as nystagmus on iris recognition systems. Also concerns have been expressed about the effect of an eye operation between registering for an iris scan system and using a terminal. Another unquantified aspect is the effect of a severe hand tremor on fingerprint recognition systems. Therefore we need research to determine how many people will be excluded and how to inclusively design the teminals.

It is worthwhile considering the needs of disabled users from the outset, since retrofitting tends to be expensive. Also good design for people with disabilities is frequently good design for everyone.

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