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ARM TrustZone is one of the most widely deployed security architecture providing Trusted Execution Environments (TEEs). Unfortunately, its usage and potential benefits for application developers and end users are largely limited due to restricted deployment policies imposed by device vendors. Restriction is enforced since every Trusted App (TA) increases the TEE's attack surface: any vulnerable or malicious TA can compromise the system's security. Hence, deploying a TA requires mutual trust between device vendor and application developer, incurring high costs for both. Vendors work around this by offering interfaces to selected TEE functionalities, however, these are not sufficient to securely implement advanced mobile services like banking. Extensive discussion of Intel's SGX technology in academia and industry has unveiled the demand for an unrestricted use of TEEs, yet no comparable security architecture for mobile devices exists to this day. We propose SANCTUARY, the first security architecture which allows unconstrained use of TEEs in the TrustZone ecosystem without relying on virtualization. SANCTUARY enables execution of security-sensitive apps within strongly isolated compartments in TrustZone's normal world comparable to SGX's user-space enclaves. In particular, we leverage TrustZone's versatile Address-Space Controller available in current ARM System-on-Chip reference designs, to enforce two-way hardware-level isolation: (i) security-sensitive apps are shielded against a compromised normal-world OS, while (ii) the system is also protected from potentially malicious apps in isolated compartments. Moreover, moving security-sensitive apps from the TrustZone's secure world to isolated compartments minimizes the TEE's attack surface. Thus, mutual trust relationships between device vendors and developers become obsolete: the full potential of TEEs can be leveraged. We demonstrate practicality and real-world benefits of SANCTUARY by thoroughly evaluating our prototype on a HiKey 960 development board with microbenchmarks and a use case for one-time password generation in two-factor authentication.

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Abstract. In this paper we show how Isolated Execution Environments (IEE) offered by novel commodity hardware such as Intel's SGX provide a new path to constructing general secure multiparty computation (MPC) protocols. Our protocol is intuitive and elegant: it uses code within an IEE to play the role of a trusted third party (TTP), and the attestation guarantees of SGX to bootstrap secure communications between participants and the TTP. The load of communications and computations on participants only depends on the size of each party's inputs and outputs and is thus small and independent from the intricacies of the functionality to be computed. The remaining computational load-essentially that of computing the functionality -is moved to an untrusted party running an IEE-enabled machine, an attractive feature for Cloud-based scenarios. Our rigorous modular security analysis relies on the novel notion of labeled attested computation which we put forth in this paper. This notion is a convenient abstraction of the kind of attestation guarantees one can obtain from trusted hardware in multi-user scenarios. Finally, we present an extensive experimental evaluation of our solution on SGXenabled hardware. Our implementation is open-source and it is functionality agnostic: it can be used to securely outsource to the Cloud arbitrary off-the-shelf collaborative software, such as the one employed on financial data applications, enabling secure collaborative execution over private inputs provided by multiple parties. IntroductionSecure multiparty computation (MPC) allows a set of mutually distrusting parties to collaboratively carry out a computation that involves their private inputs. The security guarantee that parties get are essentially those provided by carrying out the same computation using a Trusted Third Party (TTP). The computations to be carried out range from simple functionalities, for example where a party commits to a secret value and later on reveals it; or they can be highly complex, for example running sealed bid auctions [11] or bank customer benchmarking [20]. Most of the existent approaches are software only. The trust barrier between parties is overcome using cryptographic techniques that permit computing over encrypted and/or secret-shared data [35,28,19]. Another approach first studied by Katz [31] formalizes a trusted hardware assumptionwhere users have access to tamper-proof tokens on which they can load arbitrary codethat is sufficient to bootstrap universally composable MPC.Broadly speaking, this work fits within the same category as that by Katz [15]. However, our starting point is a novel real-world form of trusted hardware that is currently shipped on commodity PCs: Intel's Software Guard Extensions [30]. Our goal is to leverage this hardware to significantly reduce the computational costs of practical secure computation protocols. The main security capability that such hardware offers are Isolated Execution Environments (IEE) -a powerful tool for boosting trust in remote systems under the tot...

Embedded computing devices are used on a large scale in the emerging internet of things (IoT). However, their wide deployment raises the incentive for attackers to target these devices, as demonstrated by several recent attacks. As IoT devices are built for long service life, means are required to protect sensitive code in the presence of potential vulnerabilities, which might be discovered long after deployment. Tagged memory has been proposed as a mechanism to enforce various fine-grained security policies at runtime. However, none of the existing tagged memory schemes provides efficient and flexible compartmentalization in terms of isolated execution environments. We present TIMBER-V, a new tagged memory architecture featuring flexible and efficient isolation of code and data on small embedded systems. We overcome several limitations of previous schemes. We augment tag isolation with a memory protection unit to isolate individual processes, while maintaining low memory overhead. TIMBER-V significantly reduces the problem of memory fragmentation, and improves dynamic reuse of untrusted memory across security boundaries. TIMBER-V enables novel sharing of execution stacks across different security domains, in addition to interleaved heaps. TIMBER-V is compatible to existing code, supports real-time constraints and is open source. We show the efficiency of TIMBER-V by evaluating our proofof-concept implementation on the RISC-V simulator.