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T215B > Biometrics > Flashcards

Biometrics Flashcards

1
Q

Biometric

A

relates to a measurement or a set of measurements of human beings that can be used to identify them in the context of authentication

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2
Q

A biometric security systems

A

Are security systems that are able to recognize the identities of individuals based on one or more of their biometrics.
Such systems are often linked to or are a part of an authorization system, which decides to allow or deny access to a protected area based on one or more tests to authenticate their identity

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3
Q

Give examples on biometrics in use or have the potential of being used

A

A face, iris pattern, fingerprint, voice, DNA, gait (the way someone walks), the way someone signs their name, personal odor, and typing pattern (the way someone logs in to their computer

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4
Q

Biometrics can be divided into two types:

A

1) Physiological biometrics (like fingerprints)
2) Behavioral biometrics (like gait or name signature)

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5
Q

What is the difference between

A

Physiological biometrics do not normally change through a person’s life – at least not until they’ve reached adulthood
Behavioral biometrics can change, like how a person signs can change throughout the years, but several behavioral biometrics do not normally change unless the person intends so

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6
Q

Biometric security system main advantage

A

1) people automatically have their identity token with them
2) a biometric cannot be forgotten or left behind

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7
Q

Biometric security system main drawbacks

A

Many biometrics are not secret and so can be imitated

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8
Q

Gait

A

A behavioral biometric, which is the way someone walks

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9
Q

Advantages of Gait

A

1)can be captured from a distance
2)can be captured without the subject’s knowledge

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10
Q

Disadvantages of Gait

A

1) it is relatively hard to capture, normally involving working on a video sequence
2) it is also computationally intensive and is not suitable for real-time authentication

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11
Q

Fingerprint

A

a physiological biometric that has to do with the ridges and furrows on a fingertip

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12
Q

Advantages of fingerprints

A

1) the ridge pattern stays the same throughout a person’s life (though it may become less pronounce) unless the fingertip has been damaged
2) it is highly distinctive (even identical twins have different fingerprints)
3) a fingertip is easy to capture

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13
Q

Disadvantages of fingerprints

A

1) An estimated 5% of people are not able to provide a fingerprint that is usable for security purposes due to injury or worn-down ridges on the fingertip
2) it is possible to lift off a fingerprint of a surface and use it to produce a “fake finger”

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14
Q

Iris pattern

A

A physiological biometric where there’s a pattern on a person’s iris

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15
Q

Advantages of iris pattern

A

Each eye and every person has a unique iris pattern

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16
Q

Disadvantages of iris pattern

A

1) the capture requires the subject’s cooperation because it has to be at a correct and close distance
2) For some subjects, the light shone on their eyes can cause irritation

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17
Q

The way someone signs their name

A

A behavioral biometric, includes the way the pen moves and the pressure exerted (the signature itself is different from the pen movement)

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18
Q

Advantages and disadvantages of the way someone sign their name as a biometric

A

Advantage: it could be acceptable as the signature itself
Disadvantage: the way people sign tends to change with time

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19
Q

Typing pattern (the way a person logs in to their computer)

A

A behavioral biometric in which the way the keys are pressed, the pressure with which each key is tapped, and the intervals between key taps, etc.

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20
Q

Advantages of typing pattern

A

1) has the potential to replace signatures for computer-based activities
2) its capture does not require the subject’s cooperation as the computer could be set up to capture it automatically at log in

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21
Q

Disadvantages of typing pattern

A

Underdeveloped

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22
Q

Personal odor

A

A physiological biometric that’s a little unrealistic and the devices used to capture a personal odor could and can be very expensive

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23
Q

Face

A

A physiological biometric that is a set of measurements relating to various features

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24
Q

Disadvantages of face recognition

A

Electronic equipment has difficulty with facial recognition for several reasons
1) Face characteristics changes with the effects of aging, facial expressions, disguises, different angles of the face to the camera and different lighting conditions.
2) Close relatives might have very similar facial features
3)At present, use of this biometric requires the subject’s cooperation as they must stand a certain distance from a camera.

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25
Q

Voice

A

Can be classified as both physiological biometric if components such as frequency is measured and can be classified into behavioral biometric because it can relate to the way a person speaks

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26
Q

Advantage of voice recognition

A

1) Voice recognition is useable at a significant distance

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27
Q

Disadvantages of voice recognition

A

1) humans can recognize voices much better than electronic equipment can
2) human voices can change for various reasons such as a sore throat, so it’s not very practical
3) some people or relatives can have very similar voices
4) background noise is a problem for such a system
5) a subject’s voice could be recorded without their knowledge and used to fool the recognition system

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28
Q

Characteristics of biometrics

A

1) Distinctiveness
2) Permanence
3)Universality
4)Collectability
5)Acceptability
6)Performance
7)Circumvention

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29
Q

The architecture of biometric systems consist of:

A

1)Sensors
2)Feature extractor
3)The storage
4) The matcher
5)The decision maker

30
Q

Sensors

A

They’re devices that capture raw biometric data of users.
They can either require contact with the biometric input or be contactless
They influence the system’s convenience of use, acceptability, and reliability and influence how secure a system is

31
Q

Feature extractor

A

Takes the raw data from sensors as input, extracts from it the key features and converts them into a digital representation called a template.
It can be seen as a form of non-reversible compression.
Some systems encrypt the templates so that the data is better protected.

32
Q

Aims of a feature extractor

A
  • To reduce the complexity of the original biometric sample
  • To decrease the resources required to store and process the biometric
  • To prevent the original biometric data from being reconstructed from the template.
33
Q

The storage

A

It is a place to hold templates, and the templates enrolled into the storage need to be protected and backed up.
If a remote server is used, a secure communication link between the security system and the server is needed.

34
Q

Examples of storage devices:

A
  • Local storage medium: such as a smart card.
  • The storage facilities of a computer: (hard disk).
  • A remote server: The benefit of storing a database of templates on a server is that multiple security systems can share the data.
35
Q

The matcher

A

Compares the template created from an input biometric sample (the template outputted from the feature extractor) with a
stored template. It measures the similarity (or differences) between the two templates and produces a quantitative reference such as a similarity value.

36
Q

The decision maker

A

It measures the similarity (or differences) between the two templates and produces a quantitative reference such as a similarity value.

37
Q

The decision maker must be able to tolerate:

A

1) Intra-class differences: the differences between templates of the same individual because each template from the same individual is likely to be slightly different due to many non-repeatable variations
2) Inter-class differences: the differences between the templates of different individuals

38
Q

The sensitivity of the decision maker is controlled by one or more thresholds

A

The threshold is usually set by the system administrator based on the level of security required and operational statistics.

39
Q

Biometric security systems operation modes:

A

1) Enrollment mode
2) Recognition mode

40
Q

Enrollment mode

A

1) A user’s biometric data is captured by the sensors and then passed to the feature extractor to generate a template
2) The template then will be subsequently sent over to the storage medium for safe keeping
- To combat intra-class differences (inter-class) and enhance the system’s reliability, the system usually enrolls multiple templates of the same individual
- Biometric templates are correctly associated with the user’s identity

41
Q

Recognition mode

A

1)A user’s biometric data is captured by sensors and then passed to the feature extractor to generate a template
2)The matcher compares the newly created biometric with one or more stored templates
3) The decision maker then takes into account the similarity measured produced by the matcher
4) The decision maker then decides whether the input template matches the stored templates for that individual.

42
Q

What is the difference between identification and authentication systems?

A
43
Q

Identification

A

Refers to a process of identifying one individual from a population of individuals. It is a one-to-many comparison process.

44
Q

During an identification process:

A

1) A biometric sample is taken from the individual and converted into a template
2) This template is compared in turn with each template in the database
- if only one exact match is found, then the individual has been identified
- when no exact match is found, the system will offer the best matches instead, along with similarity values

45
Q

Authentication

A

Refers to a process of confirming whether an individual is who he or she claims to be. It is a one-to-one comparison process

46
Q

During an authentication process:

A

1) A ‘live’ biometric sample is taken from the individual and converted into a template
2) This template is compared with stored templates of the same individual

47
Q

How is a template created?

A

By establishing sufficient reference points on the face and measuring the lengths between the reference points, it is possible to create a template that uniquely represents an individual

48
Q

In a fingerprint, the most important features are the ridge configurations

A

The ridge configurations are the way the ridge lines and the valleys between them are arranged.

49
Q

The configuration of the ridge lines can be analyzed at three different levels

A

1) Global level
2) Local level
3) Micro level

50
Q

Global level

A

At the global levels, the attention is paid to singularities

51
Q

Singularities

A

Are regions where the ridge lines form high-curvature shapes.

52
Q

Singularities are classified into three main types:

A

1) Loop (can be broken down into left loop and right loop)
2) Whorl
3) Delta (can be broken down into normal arches and tented arches)
so overall 5 types

53
Q

Local level

A

At the local level, attention is paid to the ridge lines individually to identify where a ridge line is discontinuous

54
Q

Minutiae

A

Discontinuity points

55
Q

The most common types of minutiae are:

A

-Termination
-Bifurcation
-Lake
-Independent ridge
-Spur or cross over
-Island or point

56
Q

Micro level

A

At the micro level, the fine intra-ridge details are of interest.

57
Q

There are two main fingerprint sensor types:

A

1) Optical sensors
2) Solid state sensors

58
Q

Optical sensors

A

Capture images of fingerprints by using light-sensitive sensors to convert optical patterns into electrical signals

59
Q

The principal types of sensing element used in optical sensors

A

1)Charge-coupled devices (CCD)
2)CMOS-based image sensors (complementary metal oxide silicon)

60
Q

Optical sensors work by:

A

1)shining light on the fingertip, which is placed on the transparent sensing surface of the sensor
2)detecting the light reflected back on to the light sensitive sensors
-Ridges appear dark because they’re in contact with the sensing surface, so they either scatter or absorb the light
-valleys appear light because they’re at a distance from the surface,

61
Q

Pros and cons of optical sensors:

A

-They’re able to capture high-quality fingerprint images
-It’s physical size is much bigger than a solid state sensor
-It cannot be used in technologies such as computers

62
Q

Solid-state sensors

A

consists in an all-in-one silicon chip with a two-dimensional sensory array placed directly on the chip. Solid- state-sensors convert thermal, capacitive, or electric field information into electrical signals

63
Q

A ridge orientation image

A

is a simplified version of the fingerprint
image that has short lines with appropriate slopes instead of ridge lines.

64
Q

Turning a raw fingerprint image into a set of minutiae usually requires three main stages of processing:

A
  1. Binarisation
  2. Thinning
  3. minutiae detection
65
Q

Binarisation

A

is a process of converting the greyscale raw
fingerprint image into a black and white, or binary, image. It’s easier to extract out the ridges when all pixels are in black and white

66
Q

How does the binarisation process work?

A
  • The binarisation makes use of either a global threshold or a number of regional or local threshold values.
    1- It scans through all the pixels of an image and compares each pixel’s greyscale value (0 to 255 in an 8-bit greyscale image) to the threshold value
    2- If the pixel value is greater than the threshold, it’s represented by a 1, otherwise it’s represented by a 0
67
Q

Why is the appropriateness of the threshold crucial in binarisation?

A
  • Setting the threshold too high will result in ridges becoming too thick (a thick ridge can merge with neighboring ridges)
  • Setting the threshold too low will make the ridges too thin (resulting ridge can hence be full of gaps or even disappear)
68
Q

Give an example of statistical information about the fingerprint used to define a threshold (in binarisation)

A

Average intensity of the whole fingerprint

69
Q

Mention other processing techniques that can be used to enhance the quality of the whole fingerprint (in binarisation)

A

Filtering
Filling the gaps within individual ridges
Smoothing the ridges

70
Q

Thinning

A

Reduces the width of each ridge to one pixel.
A common thinning technique is to iteratively erode the black elements of the image until they become one pixel thick

71
Q

Minutiae Detection

A

consists in running an image window that in 3x3 pixels through the thinned fingerprint image and checking the black pixels within the window
The pixel in the middle of the window is the one of interest

72
Q

Minutiae Detection, explain the process that happens within the window:

A
  • If the pixel in the middle is not black, it cannot be a minutia
  • If the pixel in the middle is black:
    • If only one of its eight neighboring pixels is black, its a termination
    • If two of its eight neighboring pixels are black and they’re situated at opposite sides of the center point: an intermediate ridge point
    • If three of its eight neighboring pixels are black and one of them is situated at the opposite side of the point of interest from the other two: a bifurcation

T215B (10 decks)

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