Smartphones provide access to increasing amounts of personal and sensitive information, yet are often only secured using methods that are prone to observational attacks. We present HapticLock, a novel authentication method for mobile devices that uses non-visual interaction modalities for discreet PIN entry that is difficult to attack by shoulder surfing. A usability experiment (N=20) finds effective PIN entry in secure conditions: e.g., in 23.5s with 98.3% success rate for a four-digit PIN entered from a random start digit. A shoulder surfing experiment (N=15) finds that HapticLock is highly resistant to observational attacks. Even when interaction is highly visible, attackers need to guess the first digit when PIN entry begins with a random number, yielding a very low success rate for shoulder surfing. Furthermore, a device can be hidden from view during authentication. Our use of haptic interaction modalities gives privacy-conscious mobile device users a usable and secure authentication alternative for sensitive situations.

When users are undertaking mentally demanding visuals tasks, it can be beneficial to convey information through the auditory or tactile modality instead. A fundamental problem when mapping information to sound or vibration is establishing which polarity the mapping should use. Magnitude estimation is a popular method of establishing polarity preferences, however the effectiveness of this approach remains unclear, especially in more ecologically valid contexts. We investigate what impact the polarity of a data-sound or data-vibration mapping has on how well users can interpret these mappings, under two different levels of mental workload. Our results show that polarity does not affect error rate or cognitive workload, although may affect response time. We also found that induced cognitive load may influence usability. An implication of this is that commonly used methods of establishing data mappings need to be revisited, with cognitive load in mind, to help designers create more usable auditory and vibrotactile displays.

Dynamic personal data based on a user’s activity, such as recent visited physical locations, browsing history, and call logs, update frequently, making it a promising token for user authentication. However, it is not clear how users perceive this use of personal data and which data types are most suitable for authentication. To investigate this, we conducted an online survey with N=100 participants. For 10 personal data types we asked participants about their comfort with this data for authentication, its perceived security, its impact on behaviour, who has access to it, how frequently it updates, and how memorable they perceive it to be. We found that participants were generally uncomfortable with personal data being used for authentication and, knowing their personal data is used, they may intentionally change their behaviour due to privacy concerns. We discuss the benefits and drawbacks of using personal data as a source of dynamic tokens to complement authentication and conclude with three learned lessons.

The relationships between sounds and their perceived meaning and connotations are complex, making auditory perception an important factor to consider when designing sonification systems. Listeners often have a mental model of how a data variable should sound during sonification and this model is not considered in most data:sound mappings. This can lead to mappings that are difficult to use and can cause confusion. To investigate this issue, we conducted a magnitude estimation experiment to map how roughness, noise and pitch relate to the perceived magnitude of stress, error and danger. These parameters were chosen due to previous findings which suggest perceptual congruency between these auditory sensations and conceptual variables. Results from this experiment show that polarity and scaling preference are dependent on the data:sound mapping. This work provides polarity and scaling values that may be directly utilised by sonification designers to improve auditory displays in areas such as accessible and mobile computing, process-monitoring and biofeedback.

Sonification designers have little theory or experimental evidence to guide the design of data-to-sound mappings. Many mappings use acoustic representations of data values which do not correspond with the listener's perception of how that data value should sound during sonification. This research evaluates data-to-sound mappings that are based on psychoacoustic sensations, in an attempt to move towards using data-to-sound mappings that are aligned with the listener's perception of the data value's auditory connotations. Multiple psychoacoustic parameters were evaluated over two experiments, which were designed in the context of a domain-specific problem - detecting the level of focus of an astronomical image through auditory display. Recommendations for designing sonification systems with psychoacoustic sound parameters are presented based on our results.