The concept of privacy shields or privacy screens is not new, but recent interest has concentrated on shields on keypads to alleviate the problem of security of PINs from cashiers, other customers ("shoulder surfers") and CCTV operators.
In general, it is recommended that the user ensures maximum privacy by positioning his/her hands and body so that they shield the keypad and/or screen. However the required actions cannot always be achieved with ease. Poor manual dexterity, for example, can limit the number of simultaneous actions that can be carried out using both hands. Likewise the ability of a customer to shield the keypad and screen with his/her body will depend on the height at which the keypad and screen are located. A person of small stature or a person in a wheelchair may not be sufficiently high to block the keypad and screen from the view of other people. Although privacy shields should serve to alleviate these problems, there have been difficulties in implementing privacy shields without reducing accessibility.
Privacy screens have been designed to limit the angle at which the screen can be viewed. One method has been similar in concept to a Venetian blind. There are different types of material that can be used to achieve this effect, but all work on the same general principle: incorporation of an extra layer of material into the screen restricts the angle at which the screen contents are visible.
With respect to accessibility, one negative effect of this approach is to increase the distance between the front of the display and the image; this exacerbates the parallax problem for users of non-standard height (e.g. tall people and wheelchair users).
The sides of the privacy shield can be angled inwards to give more room around the keypad, but this increases the total area taken up by the keypad.
A possible alternative is to have a removable (e.g. hinged) privacy shield for people who have problems in using the keypad when the shield is in place. However this may be difficult to make vandal resistant, and it may be difficult to discourage users from removing the shield.
According to Guideline G16 of the Chip and PIN Programme (under 'Technical
and Operational Documents' in the Chip
and PIN reference library), three grades of keypad have been described.
With respect to privacy, these three grades are each accompanied by different
- For small relatively mobile PINpads (currently in use in many retail
outlets and restaurants) a minimal privacy shield has been recommended.
A shield should hide all keys from view at an angle of up to 25°
from the plane of the keypad in an arc of at least 270° from the
centre of the 5 key.
- More exposed keypads require a larger privacy shield and a viewing angle of 45° is recommended. The height of the sides should therefore be equal to half the width and the height of the front equal to half the length.
- In unattended locations it is recommended that the keypad be contained within a recess, at an angle close to horizontal. There should be a gap of no less than 50mm between the front of the machine and the nearest end of the keypad. The height of the recess should not be greater than the depth of the keypad, providing a viewing angle of 45°.