As sensors become ever more prevalent, more and more information will be collected about each of us. A longterm research question is how best to support beneficial uses while preserving individual privacy. Presence systems are an emerging class of applications that support collaboration. These systems leverage pervasive sensors to estimate end-user location, activities, and available communication channels. Because such presence data are sensitive, to achieve wide-spread adoption, sharing models must reflect the privacy and sharing preferences of the users. To reflect users' collaborative relationships and sharing desires, we introduce CollaPSE security, in which an individual has full access to her own data, a third party processes the data without learning anything about the data values, and users higher up in the hierarchy learn only statistical information about the employees under them. We describe simple schemes that efficiently realize CollaPSE security for time series data. We implemented these protocols using readily available cryptographic functions, and integrated the protocols with FXPAL's myUnity presence system.
A recent national survey suggests that the HIPAA privacy rule has not only failed to preserve patient privacy adequately, but also has had a negative impact on clinical research. Our work suggests that researchers revisit the possibilities of homomorphic encryption and apply the techniques to secure aggregation of medical telemetry. A primary goal is to maintain the privacy of individual patient records while also allowing clinical researchers to have flexible access to aggregated information. We discuss the preliminary design of HICCUPS, a distributed system that uses homomorphic encryption to allow only the caregivers to have unrestricted access to patients' records and at the same time enable researchers to compute statistical values and aggregation functions across different patients and caregivers. In the context of processing medical telemetry, we advocate expressibility of aggregation functions more than fast computation as a primary metric of system quality.