SoK: Privacy Personalised -- Mapping Personal Attributes \& Preferences of Privacy Mechanisms for Shoulder Surfing

Shoulder surfing is a byproduct of smartphone use that enables bystanders to access personal information (such as text and photos) by making screen observations without consent. To mitigate this, several protection mechanisms have been proposed to protect user privacy. However, the mechanisms that users prefer remain unexplored. This paper explores correlations between personal attributes and properties of shoulder surfing protection mechanisms. For this, we first conducted a structured literature review and identified ten protection mechanism categories against content-based shoulder surfing. We then surveyed N=192 users and explored correlations between personal attributes and properties of shoulder surfing protection mechanisms. Our results show that users agreed that the presented mechanisms assisted in protecting their privacy, but they preferred non-digital alternatives. Among the mechanisms, participants mainly preferred an icon overlay mechanism followed by a tangible mechanism. We also found that users who prioritized out-of-device privacy and a high tendency to interact with technology favoured the personalisation of protection mechanisms. On the contrary, age and smartphone OS did not impact users' preference for perceived usefulness and personalisation of mechanisms. Based on the results, we present key takeaways to support the design of future protection mechanisms.