Tahoe - The Least-Authority Filesystem.
Zooko Wilcox-O’Hearn, Brian Warner · IACR Cryptology ePrint Archive · 2012
Tahoe is a system for secure, distributed storage. It uses capabilities for access control, cryptography for confidentiality and integrity, and erasure coding for fault-tolerance. It has been deployed in a commercial backup service and is currently operational. The implementation is Open Source.