This page looks at more esoteric biometric technologies.
It covers -
- making sense of current and emerging biometrics
chemistry and pulse - identification on the basis
of blood or pulse?
chemistry - using spectrophotometry to provide a
- smell as a personal signature
- salinity, tongue prints, nailbed scanning, neural
wave analysis interface and other exotica
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
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
Comments on 'blood type psychology' - a pseudo-science
that purports to identify an individual's character and
aptitudes on the basis of that person's blood group -
are provided elsewhere
on this site.
Enthusiasts have argued that it will be practical to use
skin chemistry for non-forensic verification and screening
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
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.
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).
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.
'Tongue-Print: A Novel Biometrics Pattern' by David Zhang,
Zhi Liu, Jing-qi Yan and Peng-fei Shi in Lecture Notes
in Computer Science (Berlin: Springer 2007) 1174-1183
proposed a tongue print biometric, explaining that
tongue is a unique organ in that it can be stuck out
of mouth for inspection, and yet it is otherwise well
protected in the mouth and is difficult to forge. The
tongue also presents both geometric shape information
and physiological texture information which are potentially
useful in identity verification applications. Furthermore,
the act of physically reaching or thrusting out is a
convincing proof for the liveness. Despite these obvious
advantages for biometrics, little work has hitherto
been done on this topic.
may wonder why!
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
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.
next part (comparison)