We address the problem of shoulder-surfing attacks on authentication schemes by proposing IllusionPIN (IPIN), a PIN-based authentication method that operates on touchscreen devices. IPIN uses the technique of hybrid images to blend two keypads with different digit orderings in such a way, that the user who is close to the device is seeing one keypad to enter her PIN, while the attacker who is looking at the device from a bigger distance is seeing only the other keypad. The user’s keypad is shuffled in every authentication attempt, since the attacker may memorize the spatial arrangement of the pressed digits. To reason about the security of IPIN, we developed an algorithm which is based on human visual perception and estimates the minimum distance from which an observer is unable to interpret the keypad of the user. We tested our estimations with 84 simulated shoulder-surfing attacks from 21 different people. None of the attacks was successful against our estimations. In addition, we estimated the minimum distance from which a camera is unable to capture the visual information from the keypad of the user. Based on our analysis, it seems practically almost impossible for a surveillance camera to capture the PIN of a smartphone user when IPIN is in use.
@cite_44: In this paper, we propose and evaluate Use Your Illusion, a novel mechanism for user authentication that is secure and usable regardless of the size of the device on which it is used. Our system relies on the human ability to recognize a degraded version of a previously seen image. We illustrate how distorted images can be used to maintain the usability of graphical password schemes while making them more resilient to social engineering or observation attacks. Because it is difficult to mentally "revert" a degraded image, without knowledge of the original image, our scheme provides a strong line of defense against impostor access, while preserving the desirable memorability properties of graphical password schemes. Using low-fidelity tests to aid in the design, we implement prototypes of Use Your Illusion as i) an Ajax-based web service and ii) on Nokia N70 cellular phones. We conduct a between-subjects usability study of the cellular phone prototype with a total of 99 participants in two experiments. We demonstrate that, regardless of their age or gender, users are very skilled at recognizing degraded versions of self-chosen images, even on small displays and after time periods of one month. Our results indicate that graphical passwords with distorted images can achieve equivalent error rates to those using traditional images, but only when the original image is known.
@cite_35: Graphical passwords are often considered prone to shoulder-surfing attacks, where attackers can steal a user's password by peeking over his or her shoulder in the authentication process. In this paper, we explore shoulder surfing defence for recall-based graphical password systems such as Draw-A-Secret and Background Draw-A-Secret, where users doodle their passwords (i.e. secrets) on a drawing grid. We propose three innovative shoulder surfing defence techniques, and conduct two separate controlled laboratory experiments to evaluate both security and usability perspectives of the proposed techniques. One technique was expected to work to some extent theoretically, but it turned out to provide little protection. One technique provided the best overall shoulder surfing defence, but also caused some usability challenges. The other technique achieved reasonable shoulder surfing defence and good usability simultaneously, a good balance which the two other techniques did not achieve. Our results appear to be also relevant to other graphical password systems such as Pass-Go.
@cite_15: In this paper we propose and evaluate new graphical password schemes that exploit features of graphical input displays to achieve better security than text-based passwords. Graphical input devices enable the user to decouple the position of inputs from the temporal order in which those inputs occur, and we show that this decoupling can be used to generate password schemes with substantially larger (memorable) password spaces. In order to evaluate the security of one of our schemes, we devise a novel way to capture a subset of the "memorable" passwords that, we believe, is itself a contribution. In this work we are primarily motivated by devices such as personal digital assistants (PDAs) that offer graphical input capabilities via a stylus, and we describe our prototype implementation of one of our password schemes on such a PDA, namely the Palm PilotTM.
The principle states that it has to be difficult to receive the visual information of interest @cite_44 . For example, DAS @cite_15 is a simple graphical password that allows the user to create a free-form drawing on a touchscreen and to use it as her password. Decoy Strokes @cite_35 is a shoulder-surfing resistant variation of DAS that draws strokes alongside the user's password to confuse a malicious observer. The problem with such schemes is that the user is exposed to the same distracting information and may end up confused as well, leading to slower authentication and more frequent input errors. Also, if the attacker is able to observe multiple times during the authentication process or to record it, he may be able to steal the credentials of the user.