As the Internet of Things (IoT) devices make their ways into people's homes, traditional dwellings are turning into smart homes. While prior empirical studies have examined people's privacy concerns of smart homes and their desired ways of mitigating these concerns, the focus was primarily on the end users or device owners. Our research investigated the privacy perceptions and design ideas of smart home bystanders, i.e., people who are not the owners nor the primary users of smart home devices but can potentially be involved in the device usage, such as other family members or guests. We conducted focus groups and co-design activities with eighteen participants. We identified three impacting factors of bystanders' privacy perceptions (e.g., perceived norms) and a number of design factors to mitigate their privacy concerns (e.g., asking for device control). We highlighted bystanders' needs for privacy and controls, as well as the tension of privacy expectations between the owners/users and the bystanders in smart homes. We discussed how future designs can better support and balance the privacy needs of different stakeholders in smart homes.

Home is a person's castle, a private and protected space. Internet-connected devices such as locks, cameras, and speakers might make a home "smarter" but also raise privacy issues because these devices may constantly and inconspicuously collect, infer or even share information about people in the home. To explore user-centered privacy designs for smart homes, we conducted a co-design study in which we worked closely with diverse groups of participants in creating new designs. This study helps fill the gap in the literature between studying users' privacy concerns and designing privacy tools only by experts. Our participants' privacy designs often relied on simple strategies, such as data localization, disconnection from the Internet, and a private mode. From these designs, we identified six key design factors: data transparency and control, security, safety, usability and user experience, system intelligence, and system modality. We discuss how these factors can guide design for smart home privacy. CCS CONCEPTS • Security and privacy → Privacy protections;