chemistries

This page looks at DNA and other more esoteric biometric technologies.

It covers -

• introduction - making sense of current and emerging biometrics
• DNA - your genes as your identifier
• blood chemistry and pulse - identification on the basis of blood or pulse?
• skin chemistry - using spectrophotometry to provide a signature
• odour - smell as a personal signature
• others - salinity, nailbed scanning, neural wave analysis interface and other exotica

    introduction

DNA has captured popular, government and scientific attention as a unique and stable identifier that is more powerful than fingerprinting. Researchers and developers have sought to leverage respect for that technology in promoting more exotic - or merely more opportunistic - biometric proposals concerning attributes such as brainwaves, pulse, personal smell and salinity or nailbeds as "a human barcode".

It is likely that most of those proposals will not get out of the laboratory (or even beyond the grant submission stage) because they do not appear to offer significant advantages over other biometric technologies and non-biometric identification mechanisms.

    DNA

Identification on the basis of an individual's unique, stable and measurable genetic characteristics has gained fundamental judicial, administrative and scientific recognition over the past two decades. DNA-based identification - based on examination of tissue, semen or other samples - appears to be highly accurate when correctly conducted (most challenges in recent years have centred on the contamination or substitution of samples) and has thus resulted in proposals for large-scale DNA registers. It has also resulted in proposals for DNA-based 'authenticity labelling' of indigenous artworks.

In practice, DNA identification is technically challenging, expensive and not particular quick (eg upwards of 15 minutes). Accordingly its use centres on retrospective forensic applications - 'who has been here' - rather than on-the-spot verification and screening.

Community perceptions differ, with studies suggesting that some people are unconcerned about DNA collection/use and that others worried about potential misuse of information in DNA registers (unsurprising given broader concerns about genetic privacy highlighted earlier in this note) or uncomfortable with perceived invasive collection mechanisms (eg providing a swab of cells from inside their mouth or a blood specimen).

Those concerns are likely to increase given recent media coverage about poor practice in the laboratory and the alleged ease of 'salting' an innocent person's DNA at a crime scene. The sci-fi film Gattaca was thus supposedly the inspiration for a DNA-substitution scam in subverting a UK community register.

    blood chemistry and pulse

Identification through blood chemistry and antibodies - with individuals supposedly having a unique and stable signature that is independent of a DNA test - has been inhibited by questions about its scientific basis and its invasive nature, with subjects being required to supply one or more blood samples (for example a drop being taken from a thumb prick).

Other researchers have proposed heart rhythm or blood pulse biometrics, with the latter involving use of infrared sensors to measure the pulse in a finger. The technology appears to have a high false match rate (between individuals and between the same individual on different occasions), with critics suggesting that it will thus not emerge from the laboratory.

    skin chemistry

Enthusiasts have argued that it will be practical to use skin chemistry for non-forensic verification and screening of people.

It is claimed that the chemical composition of individuals is distinctive and measurable. Skin chemistry biometrics centre on use of spectrophotometry to measure the chemical 'signature' of skin. Typically a small patch of skin is illuminated with a beam of visible or near-infrared light, with the reflected light being measured by a spectroscope that allows determination of a supposedly unique numerical value.

Application of the technology outside the laboratory has been inhibited by concerns regarding environmental contamination, whether skin does have a truly unique signature and the cost of the equipment.

    odour

Enthusiasts have suggested that an array of sophisticated sensors and software would be able to identify individuals on the basis of personal odour by 'sniffing' the air around that person. The identification would be independent of sniffing to detect the individual's contact with explosives, illicit drugs or other chemicals. Supposedly each individual has a recognisable and stable smell.

Critics have unsurprisingly labelled that notion as junk science, arguing that a high level of false negatives/positives is inevitable because devices will be affected by atmospheric pollution - particularly in locations such as airports - and that the individual 'signature' is affected by factors such as health, age, diet and exposure to contaminants. Proponents have yet to make a compelling case for using odor recognition rather than another biometric or non-biometric identity verification/screening mechanism.

An introduction is provided by Zhanna Korotkaya's 2003 Biometric Person Authentication: Odor (PDF).

    others

Scepticism about extension of research outside the laboratory (or even about the genuineness of research) is evident in responses to a range of other mooted biometrics, such as body salinity, nailbed identification, acoustic head resonance and neural wave analysis interface.

Proponents of body salinity as a biometric envisage passing a nano-amp current through the subject. The conductivity would, it is claimed, be affected by the level of salt in the blood. Criticism centres on objections that readings may not be distinctive and invariant - testing of an individual on two occasions might produce two distinct results; two individuals might have the same result. The testing would apparently involve a naked subject - a substantial impediment to use in most environments - and we wonder whether other mechanisms are both easier and more reliable. The technology has, however, attracted attention from researchers exploring use of skin as a transmitter for information housed in a subdermal chip or in a bracelet or other device, typically being connected to a network by placing a finger on a reader.

Neural wave analysis interface (NWAI) has attracted attention for supposed funkiness and as a potential spin-off of research into 'thought-activated interfaces' (eg tools for fighter pilots and aids for the physically disabled). NWAI (Neural Wave Analysis Interface). The technology centres on measurement of brain waves (eg the electroencephalogram) or bioelectrical impulses governing the operation of muscles.

It is, however, unclear whether individuals have a truly distinct and invariant neural wave 'signature' that can be readily measured for the purposes of verification or screening. Other identification mechanisms would currently appear to be more effective.

Nailbed identification technology is predicated on measurement of ridges in the epidermal structure directly under each fingernail and in the inner surface of the nail (the keratin), supposedly unique and promoted as "the human barcode". Proponents envisage that an interferometer would be used to detect phase changes in back-scattered light shone on a nail, resulting in a map of striations that could be expressed as a numerical code.

The technology does not appear to be commercially available; proposals suggest that a specialist device would be manufactured for use at building or network access points, with the subject inserting a finger into the reader. As with NWAI, it is unclear whether the 'signature' is truly distinct - we are unaware of large scale research on nailbed characteristics - and more seriously whether there are simply easier ways of identifying people that zapping their paws with polarised light.

Acoustic head resonance or skull resonance schemes - which attracted shortlived media attention in the early 1990s - involve passing a low frequency sound through a person's head, with the resonance of the skull and its contents (in the 800-900 MHz range) producing a unique 'signature' since no head is exactly the same as its peers. Unfortunately measurement appears to have been easier and more reliable when the head was separated from the body, a procedure likely to find favour with few travellers or employees. There has been less research on schemes based on whole-of-body bone sound transmission.

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