Private Join and Compute is Google's free/open source tool to allow "mulitparty computation" of encrypted data without decryption

Private Join and Compute is a new free/open Google tool that implements the longstanding cryptographic concept of "commutative encryption," which allows untrusted parties to merge their datasets without revealing their contents to one another, do mathematical work on the data, and learn the outcome of that work without either of them seeing the underlying data. Read the rest