  A growing number of devices and services collect detailed time series data
that is stored in the cloud. Protecting the confidentiality of this vast and
continuously generated data is an acute need for many applications in this
space. At the same time, we must preserve the utility of this data by enabling
authorized services to securely and selectively access and run analytics. This
paper presents TimeCrypt, a system that provides scalable and real-time
analytics over large volumes of encrypted time series data. TimeCrypt allows
users to define expressive data access and privacy policies and enforces it
cryptographically via encryption. In TimeCrypt, data is encrypted end-to-end,
and authorized parties can only decrypt and verify queries within their
authorized access scope. Our evaluation of TimeCrypt shows that its memory
overhead and performance are competitive and close to operating on data in the
clear.
