Private Delegated Computations Using Strong Isolation
Mathias Brossard, Guilhem Bryant, Basma El Gaabouri, Xinxin Fan, Alexandre Ferreira, Edmund Grimley Evans, Christopher Haster, Evan Johnson, Derek Miller, Fan Mo, Dominic P. Mulligan, Nick Spinale, Eric Van Hensbergen, Hugo J. M. Vincent, Shale Xiong · IEEE Transactions on Emerging Topics in Computing · 2023
Computations are now routinelydelegatedto third-parties. In response,Confidential Computingtechnologies are being added to microprocessors offering atrusted execution environment(TEE) that provides confidentiality and integrity guarantees to code and data hosted within—even in the face of a privileged attacker. TEEs, along with an attestation protocol, permit remote third-parties to establish a trusted “beachhead” containing known code and data on an otherwise untrusted machine. Yet, they introduce many new problems, including: how to ease provisioning of computations safely into TEEs; how to develop distributed systems spanning multiple classes of TEE; and what to do about the billions of “legacy” devices without support for Confidential Computing? Tackling these problems, we introduceVeracruz, a pragmatic framework that eases the design and implementation of complex privacy-preserving, collaborative, delegated computations among a group of mutually mistrusting principals. Veracruz supports multiple isolation technologies and provides a common programming model and attestation protocol across all of them, smoothing deployment of delegated computations over supported technologies. We demonstrate Veracruz in operation, on private in-cloud object detection on encrypted video streaming from a video camera. In addition to supporting hardware-backed TEEs—like AWS Nitro Enclaves and Arm Confidential Computing Architecture Realms—Veracruz also provides pragmatic “software TEEs” on Armv8-A devices without hardware Confidential Computing capability, using the high-assuranceseL4microkernel and ourIceCapframework.