Separate but Together: Integrating Remote Attestation into TLS

Confidential computing based on Trusted Execution Environments (TEEs) allows software to run on remote servers without trusting the administrator. Remote attestation offers verifiable proof of the software stack and hardware elements comprising the TEE. However, setting up a secure channel to such a TEE requires a security guarantee that the channel actually terminates inside the TEE. TLS is an existing protocol for secure channel establishment, and in its most common use on the Web, it uses a key pair to assert the server identity encoded in a certificate. Various approaches have been proposed to integrate remote attestation into TLS. Unfortunately, they all have shortcomings. In this paper, we present a protocol that combines the existing certificate-based assurances of TLS with remote attestation-based assurances in a way that they can be deployed independently and can fail independently. We design these two assurances to be additive without relying on each other, a property that has not been considered by existing approaches.