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Remote attestation (RA) authenticates code running in trusted execution environments (TEEs), allowing trusted code to be deployed even on untrusted hosts. However, trust relationships established by one component in a distributed application may impact the security of other components, making it difficult to reason about the security of the application as a whole. Furthermore, traditional RA approaches interact badly with modern web service design, which tends to employ small interacting microservices, short session lifetimes, and little or no state. This paper presents the Decent Application Platform, a framework for building secure decentralized applications. Decent applications authenticate and authorize distributed enclave components using a protocol based on self-attestation certificates, a reusable credential based on RA and verifiable by a third party. Components mutually authenticate each other not only based on their code, but also based on the other components they trust, ensuring that no transitively-connected components receive unauthorized information. While some other TEE frameworks support mutual authentication in some form, Decent is the only system that supports mutual authentication without requiring an additional trusted third party besides the trusted hardware's manufacturer. We have verified the secrecy and authenticity of Decent application data in ProVerif, and implemented two applications to evaluate Decent'smore »
We present the Flow-Limited Authorization First-Order Logic (FLAFOL), a logic for reasoning about authorization decisions in the presence of information-flow policies. We formalize the FLAFOL proof system, characterize its proof-theoretic properties, and develop its security guarantees. In particular, FLAFOL is the first logic to provide a non-interference guarantee while supporting all connectives of first-order logic. Furthermore, this guarantee is the first to combine the notions of non-interference from both authorization logic and information-flow systems. All the theorems in this paper are proven in Coq.
Byzantine Fault Tolerant (BFT) protocols are designed to ensure correctness and eventual progress in the face of misbehaving nodes . However, this does not prevent negative effects an adversary may have on performance: a faulty node may significantly affect the latency and throughput of the system without being detected. This is especially true in speculative protocols optimized for the best-case where a single leader can force the protocol into the worst case . Systems like Aardvark  that are designed to maximize worst-case performance tolerate byzantine behavior without necessarily detecting who the perpetrator is. By forcing regular view changes, for example, they mitigate the effects of leaders who deliberately delay dissemination of messages, even if this behavior would be difficult to prove to a third party. Byzantine faults, by definition, can be difficult to detect. An error of 'commission', such as a message with a mismatching digest, can be proven. Errors of 'omission', such as delaying or failing to relay a message, as a rule cannot be proven, and the node responsible for these types of omission faults may not appear faulty to all observers. Nevertheless, we observe that they can reliably be detected. Designing protocols that detect and ejectmore »
Distributed applications cannot assume that their security policies will be enforced on untrusted hosts. Trusted execution environments (TEEs) combined with cryptographic mechanisms enable execution of known code on an untrusted host and the exchange of confidential and authenticated messages with it. TEEs do not, however, establish the trustworthiness of code executing in a TEE. Thus, developing secure applications using TEEs requires specialized expertise and careful auditing. This paper presents DFLATE, a core security calculus for distributed applications with TEEs. DFLATE offers high-level abstractions that reflect both the guarantees and limitations of the underlying security mechanisms they are based on. The accuracy of these abstractions is exhibited by asymmetry between confidentiality and integrity in our formal results: DFLATE enforces a strong form of noninterference for confidentiality, but only a weak form for integrity. This reflects the asymmetry of the security guarantees of a TEE: a malicious host cannot access secrets in the TEE or modify its contents, but they can suppress or manipulate the sequence of its inputs and outputs. Therefore DFLATE cannot protect against the suppression of high-integrity messages, but when these messages are delivered, their contents cannot have been influenced by an attacker.