UC Santa Cruz

The core principles of information security — Confidentiality, Integrity, and Availability — are increasingly challenged as modern applications rely heavily on remote services to provide essential functionalities. Offloading complex computations to powerful servers and synchronizing user data across multiple devices have become common practice. This system model typically involves a large number of users, a service provider, third-party services, and cloud providers.

In this setup, users must trust both service providers and cloud providers to protect their data and deliver services as promised. Similarly, service providers rely on cloud providers to secure their data and ensure service integrity. This trust model is largely based on legal frameworks and the reputations of the service and cloud providers. However, such mechanisms can only offer compensation after a breach occurs; they do little to prevent potential damage. Thus, a verifiable and decentralized trust model that can proactively ensure application security is highly desirable. Existing solutions, such as End-to-End Encryption, Fully Homomorphic Encryption, and Multi-Party Computation, offer only limited functionalities, are computationally expensive, or focus primarily on confidentiality and integrity while providing little to no availability guarantees.

In this dissertation, we propose the Decent Framework, a novel approach to building secure distributed applications. The Decent Framework integrates secure enclaves with blockchain technology to provide comprehensive Confidentiality, Integrity, and Availability guarantees. A secure enclave is a cryptographically protected memory region, isolated from the rest of the system, including the operating system, ensuring confidentiality and integrity of the data and code within. Meanwhile, blockchain technology achieves high availability through global replication across thousands or even millions of nodes.

However, several challenges arise in building this framework. The native remote attestation protocol introduces significant overhead for short-lived serverless components and lacks support for mutual attestation. To address this, the Decent Framework introduces self-attestation certificates, which reduce the overhead of remote attestation significantly. By embedding an AuthList within the certificate, it enables enclaves to authenticate each other without relying on a trusted third party.

Additionally, enclaves are susceptible to eclipse attacks, where an attacker controls all network connections to the enclave, making it difficult to determine the legitimacy of received blockchain data. On the blockchain side, no existing work addresses the challenge of performing remote attestation on-chain or verifying enclave RA reports and signatures. We present a novel algorithm that reliably detects eclipse attacks by monitoring fluctuations in block difficulty.

To provide message availability in the Decent Framework, we developed Decentagram, a highly available publish/subscribe system that guarantees the timely delivery of critical messages. Decentagram also implements revocation mechanisms to distribute component revocation lists to enclaves within the system. Finally, we introduce AlacriTEE, a fully decentralized Function-as-a-Service (FaaS) platform built on secure enclaves and blockchain, which ensures the availability and integrity of services provided by enclave components.