WebAssembly (WASM) is an immensely versatile and increasingly popular compilation target. It executes applications written in several languages (e.g., C/C++) with near-native performance in various domains (e.g., mobile, edge, cloud). Despite WASM's sandboxing feature, which isolates applications from other instances and the host platform, WASM does not inherently provide any memory safety guarantees for applications written in low-level, unsafe languages. To this end, we propose Cage, a hardware-accelerated toolchain for WASM that supports unmodified applications compiled to WASM and utilizes diverse Arm hardware features aiming to enrich the memory safety properties of WASM. Precisely, Cage leverages Arm's Memory Tagging Extension (MTE) to (i) provide spatial and temporal memory safety for heap and stack allocations and (ii) improve the performance of WASM's sandboxing mechanism. Cage further employs Arm's Pointer Authentication (PAC) to prevent leaked pointers from being reused by other WASM instances, thus enhancing WASM's security properties. We implement our system based on 64-bit WASM. We provide a WASM compiler and runtime with support for Arm's MTE and PAC. On top of that, Cage's LLVM-based compiler toolchain transforms unmodified applications to provide spatial and temporal memory safety for stack and heap allocations and prevent function pointer reuse. Our evaluation on real hardware shows that Cage incurs minimal runtime (<5.8%) and memory (<3.7%) overheads and can improve the performance of WASM's sandboxing mechanism, achieving a speedup of over 5.1%, while offering efficient memory safety guarantees.

The adoption of wearable technologies, such as smartwatches or wristbands, is rising. End-users expect to use all of their devices in an interconnected and seamless manner to conduct digital transactions, e.g., to pay or identify via their smartwatches, and not only via their smartphones. As sensitive transactions are usually protected by hardware-enforced isolation mechanisms, such as Trusted Execution Environments (TEEs), this brings new challenges of interconnecting TEEs to collaboratively conduct such transactions. We therefore propose MultiTEE, a distributed TEE architecture for heterogeneous device clusters, enabling secure data exchange and cooperation between TEEs. MultiTEE relies on lightweight, secure channels between TEEs, combined with remote attestation for the integrity verification of software stacks, as well as a memory-safe implementation. This enables an interface between Trusted Applications (TAs) of the distributed TEE similar to the interfaces of classic, single device TEEs. To demonstrate the feasibility of our solution, we built a Proof of Concept (PoC), partially implementing the upcoming European Digital Identity (EUDI) wallet to show the usage of heterogeneous device clusters for electronic identification. We evaluate our solution regarding performance and security.

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The majority of mobile devices today are based on Arm architecture that supports the hosting of trusted applications in Trusted Execution Environment (TEE). RISC-V is a relatively new open-source instruction set architecture that was engineered to fit many uses. In one potential RISC-V usage scenario, mobile devices could be based on RISC-V hardware. We consider the implications of porting the mobile security stack on top of a RISC-V system on a chip, identify the gaps in the open-source Keystone framework for building custom TEEs, and propose a security architecture that, among other things, supports the GlobalPlatform TEE API specification for trusted applications. In addition to Keystone enclaves the architecture includes a Trusted Hart – a normal core that runs a trusted operating system and is dedicated for security functions, like control of the device’s keystore and the management of secure peripherals. The proposed security architecture for RISC-V platform is verified experimentally using the HiFive Unleashed RISC-V development board.

Modern reduced instruction set computer processors are based on a load/store architecture, where all computations are performed on register operands. Compilers therefore allocate registers based on demand, and when occupancy is at maximum, register contents are spilled onto the stack and then retrieved later as data is needed. This phenomenon has security implications that cannot be ignored, as data on the stack is subject to well-known memory corruption attacks. Moreover, works presented so far are mainly targeting protection of pointers to code (e.g., return addresses), but are ineffective for protecting other context data in the stack. This article presents a security solution for spilled registers, generalizing the use of ARM pointer authentication (PA) for this purpose. The protection is enforced by the LLVM compiler via additional compiler passes and modifications. The solution provides guarantees for both integrity and confidentiality protection, and also addressing reuse attack problems associated with PA usage. Experimental data collected demonstrates the effectiveness of the solution against corruption and eavesdropping. We test our solution using SPEC CPU 2017, which confirms the functional viability of our solution. Additionally, we expose real-world performance overhead metrics of our protection design on a ARM-PA-enabled processor.

Software control-flow integrity (CFI) solutions have been applied to the Linux kernel for memory protection. Due to performance costs, deployed software CFI solutions are coarse grained. In this work, we demonstrate a precise hardware-assisted kernel CFI running on widely-used off-the-shelf processors. Specifically, we use the ARMv8.3 pointer authentication (PAuth) extension and present a design that uses it to achieve strong security guarantees with minimal performance penalties. Furthermore, we show how deployment of such security primitives in the kernel can significantly differ from their user space application.

Shadow stacks are the go-to solution for perfect backward-edge control-flow integrity (CFI). Software shadow stacks trade off security for performance. Hardware-assisted shadow stacks are efficient and secure, but expensive to deploy. We present authenticated call stack (ACS), a novel mechanism for precise verification of return addresses using aggregated message authentication codes. We show how ACS can be realized using ARMv8.3-A pointer authentication, a new low-overhead mechanism for protecting pointer integrity. Our solution achieves security comparable to hardware-assisted shadow stacks, while incurring negligible performance overhead (< 0.5%) but requiring no additional hardware support.

Malware checking is changing from being a local service to a cloud-assisted one where users' devices query a cloud server, which hosts a dictionary of malware signatures, to check if particular applications are potentially malware. Whilst such an architecture gains all the benefits of cloud-based services, it opens up a major privacy concern since the cloud service can infer personal traits of the users based on the lists of applications queried by their devices. Private membership test (PMT) schemes can remove this privacy concern. However, known PMT schemes do not scale well to a large number of simultaneous users and high query arrival rates. We propose a simple PMT approach using a carousel: circling the entire dictionary through trusted hardware on the cloud server. Users communicate with the trusted hardware via secure channels. We show how the carousel approach, using different data structures to represent the dictionary, can be realized on two different commercial hardware security architectures (ARM TrustZone and Intel SGX). We highlight subtle aspects of securely implementing seemingly simple PMT schemes on these architectures. Through extensive experimental analysis, we show that for the malware checking scenario our carousel approach surprisingly outperforms Path ORAM on the same hardware by supporting a much higher query arrival rate while guaranteeing acceptable response latency for individual queries.

Remote attestation is a crucial security service particularly relevant to increasingly popular IoT (and other embedded) devices. It allows a trusted party (verifier) to learn the state of a remote, and potentially malware-infected, device (prover). Most existing approaches are static in nature and only check whether benign software is initially loaded on the prover. However, they are vulnerable to runtime attacks that hijack the application's control or data flow, e.g., via return-oriented programming or data-oriented exploits. As a concrete step towards more comprehensive runtime remote attestation, we present the design and implementation of Control-FLow ATtestation (C-FLAT) that enables remote attestation of an application's control-flow path, without requiring the source code. We describe a full prototype implementation of C-FLAT on Raspberry Pi using its ARM TrustZone hardware security extensions. We evaluate C-FLAT's performance using a real-world embedded (cyber-physical) application, and demonstrate its efficacy against control-flow hijacking attacks.

Trusted computing technologies for mobile devices have been researched, developed, and deployed over the past decade. Although their use has been limited so far, ongoing standardization may change this by opening up these technologies for easy access by developers and users. In this survey, we describe the current state of trusted computing solutions for mobile devices from research, standardization, and deployment perspectives.

A trusted execution environment (TEE) is a secure processing environment that is isolated from the normal processing environment where the device operating system and applications run. The first mobile phones with hardware-based TEEs appeared almost a decade ago, and today almost every smartphone and tablet contains a TEE like ARM TrustZone. Despite such a large-scale deployment, the use of TEE functionality has been limited for developers. With emerging standardization this situation is about to change. In this tutorial, we explain the security features provided by mobile TEEs and describe On-board Credentials (ObC) system that enables third-party TEE development. We discuss ongoing TEE standardization activities, including the recent Global Platform standards and the Trusted Platform Module (TPM) 2.0 specification, and identify open problems for the near future of mobile hardware security.

The recent dramatic increase in the popularity of "smartphones" has led to increased interest in smartphone security research. From the perspective of a security researcher the noteworthy attributes of a modern smartphone are the ability to install new applications, possibility to access Internet and presence of private or sensitive information such as messages or location. These attributes are also present in a large class of more traditional "feature phones." Mobile platform security architectures in these types of devices have seen a much larger scale of deployment compared to platform security architectures designed for PC platforms. In this paper we start by describing the business, regulatory and end-user requirements which paved the way for this widespread deployment of mobile platform security architectures. We briefly describe typical hardware-based security mechanism that provide the foundation for mobile platform security. We then describe and compare the currently most prominent open mobile platform security architectures and conclude that many features introduced recently are borrowed, or adapted with a twist, from older platform security architectures. Finally, we identify a number of open problems in designing effective mobile platform security.

“Pairing” is the establishment of authenticated key agreement between two devices over a wireless channel. Such devices are ad hoc in nature as they lack any common preshared secrets or trusted authority. Fortunately, these devices can be connected via auxiliary physical (audio, visual, tactile) channels which can be authenticated by human users. They can, therefore, be used to form the basis of a pairing operation. Recently proposed pairing protocols and methods are based upon bidirectional physical channels. However, various pairing scenarios are asymmetric in nature, i.e., only a unidirectional physical channel exists between two devices (such as between a cell phone and an access point). In this paper, we show how strong mutual authentication can be achieved even with a unidirectional visual channel, where prior methods could provide only a weaker property termed as presence. This could help reduce the execution time and improve usability of prior pairing methods. In addition, by adopting recently proposed improved pairing protocols, we propose how visual channel authentication can be used even on devices that have very limited displaying capabilities, all the way down to a device whose display consists of a cheap single light-source, such as a light-emitting diode. We present the results of a preliminary usability study evaluating our proposed method.

Securely storing and using credentials is critical for ensuring the security of many modern distributed applications. Existing approaches to address this problem fall short. User memorizable passwords are flexible and cheap, but they suffer from bad usability and low security. On the other hand, dedicated hardware tokens provide high levels of security, but the logistics of manufacturing and provisioning such tokens are expensive, which makes them unattractive for most service providers. A new approach to address the problem has become possible due to the fact that several types of general-purpose secure hardware, like TPM and M-shield, are becoming widely deployed. These platforms enable, to different degrees, a strongly isolated secure environment. In this paper, we describe how we use general-purpose secure hardware to develop an architecture for credentials which we call On-board Credentials (ObCs). ObCs combine the flexibility of virtual credentials with the higher levels of protection due to the use of secure hardware. A distinguishing feature of the ObC architecture is that it is open: it allows anyone to design and deploy new credential algorithms to ObC-capable devices without approval from the device manufacturer or any other third party. The primary contribution of this paper is showing and solving the technical challenges in achieving openness while avoiding additional costs (by making use of already deployed secure hardware) and without compromising security (e.g., ensuring strong isolation). Our proposed architecture is designed with the constraints of existing secure hardware in mind and has been prototyped on several different platforms including mobile devices based on M-Shield secure hardware.

We will demonstrate a new copyright payment system for peer-to-peer file sharing. The demonstration shows a concept, which legalizes unauthorized content on users' hard disks or memory cards. The system provides a possibility to carry out payments for the content that has been downloaded at any time in the past. The system identifies and characterizes the content. According to the user selection the user can pay the copyright fees for the selected content. The copyright fees are further delivered to the respective copyright owners.

Most contemporary security mechanisms and protocols include exchange of random or time-variant nonces as an essential means of protection against replay and other threats or as a seed for randomness. In many cases, it would be beneficial to have such nonces available from a trusted common source, such as a satellite. The goal of this paper is to present a protocol by which a loosely connected network of devices can agree on a common piece of randomness, and show how it can be applied to improve efficiency of a privacy protection system and group session key exchange for PAN/LAN devices.

Recently several researchers and practitioners have begun to address the problem of how to set up secure communication between two devices without the assistance of a trusted third party. McCune et al., (2005) proposed that one device displays the hash of its public key in the form of a barcode, and the other device reads it using a camera. Mutual authentication requires switching the roles of the devices and repeating the above process in the reverse direction. In this paper, we show how strong mutual authentication can be achieved even with a unidirectional visual channel, without having to switch device roles. By adopting recently proposed improved pairing protocols, we propose how visual channel authentication can be used even on devices that have very limited displaying capabilities