ARM TrustZone Research Articles

TrustHealth: Enhancing eHealth Security with Blockchain and Trusted Execution Environments

The rapid growth of electronic health (eHealth) systems has led to serious security and privacy challenges, highlighting the critical importance of protecting sensitive healthcare data. Although researchers have employed blockchain to tackle data management and sharing within eHealth systems, substantial privacy concerns persist as a primary challenge. In this paper, we introduce TrustHealth, a secure data sharing system that leverages trusted execution environment (TEE) and blockchain technology. TrustHealth leverages blockchain to design smart contracts to offer robust hashing protection for patients’ healthcare data. We provide a secure execution environment for SQLCipher, isolating all sensitive operations of healthcare data from the untrusted environment to ensure the confidentiality and integrity of the data. Additionally, we design a TEE-empowered session key generation protocol that enables secure authentication and key sharing for both parties involved in data sharing. Finally, we implement TrustHealth using Hyperledger Fabric and ARM TrustZone. Through security and performance evaluation, TrustHealth is shown to securely process massive encrypted data flows at a rate of 5000 records per second, affirming the feasibility of our proposed scheme. We believe that TrustHealth offers valuable guidelines for the design and implementation of similar systems, providing a valuable contribution to ensuring the privacy and security of eHealth systems.

MECAT: Memory-Safe Smart Contracts in ARM TrustZone

MECAT: Memory-Safe Smart Contracts in ARM TrustZone

TEEm: Supporting Large Memory for Trusted Applications in ARM TrustZone

TEEm: Supporting Large Memory for Trusted Applications in ARM TrustZone

CacheIEE: Cache-Assisted Isolated Execution Environment on ARM Multi-Core Platforms

ARM TrustZone technology has been widely used to create Trusted Execution Environments (TEEs) for enhancing the security of applications. However, the increasing number of installed security-sensitive applications in the secure world will inevitably enlarge the trusted computing base (TCB) of TEE systems. To minimize the TCB of the secure world and increase application portability, Isolated Execution Environments (IEEs) are proposed to protect applications in enclaves created in the normal world. However, existing IEE systems cannot provide the same level of security as the TEE systems, particularly, on resolving the multi-vector attacks that include both physical memory disclosure attacks and software attacks. In this paper, we develop a new cache-assisted IEE system called CacheIEE that creates enclaves in the L1 data cache of the normal world to protect sensitive data against multi-vector attacks. First, by always storing the sensitive data in the L1 data cache, CacheIEE can effectively prevent physical memory disclosure attacks. Second, we protect the L1 data cache against untrusted rich OS running in other cores. To support more applications, CacheIEE can process large-size sensitive data in the L1 data cache with constrained capacity. We implement a system prototype of CacheIEE and verify its security and practicability.

Basic secure services for standard RISC-V architectures

Trusted Execution Environments (TEEs) have gained prominence as a means to enhance the security of complex system designs. However, TEE implementations such as ARM TrustZone and Intel SGX have been plagued by numerous vulnerabilities, prompting the research community to focus on identifying and resolving existing design flaws. Concurrently, the emergence of the RISC-V processor architecture presents an opportunity for widespread usage and customization.This research paper delves into the potential of the RISC-V architecture to incorporate TEE functionality, emphasizing the need to identify and mitigate possible pitfalls and vulnerabilities during the design phase. By examining current issues present in established TEE frameworks, we implemented and evaluated real-world services utilized by user applications and operating systems that leverage common TEE features on an up-to-date version of the standard RISC-V Instruction Set Architecture (ISA).Our findings reveal that the existing RISC-V ISA can successfully support secure file storage, cryptographic key management, and remote attestation services, employing standard-compliant unmodified RISC-V cores. However, our results also highlight the absence of mechanisms within RISC-V to ensure secure communication between the system and peripherals, thereby lacking means to interact safely with the user in the event of an operating system compromise. In conclusion, we discuss potential solutions to address this remaining challenge and suggest improvements for future research in securing communication channels and user interaction within the RISC-V architecture.

Investigating Black-Box Function Recognition Using Hardware Performance Counters

This paper presents new methods and results for recognising black-box program functions using hardware performance counters (HPC), where an investigator can invoke and measure function calls. Important use cases include analysing compiled libraries, e.g. static and dynamic link libraries, and trusted execution environment (TEE) applications. We develop a generic approach to classify a comprehensive set of hardware events, e.g. branch mis-predictions and instruction retirements, to recognise standard benchmarking and cryptographic library functions. This includes various signing, verification and hash functions, and ciphers in numerous modes of operation. Three architectures are evaluated using off-the-shelf Intel/X86-64, ARM, and RISC-V CPUs. Next, we show that several known CVE-numbered OpenSSL vulnerabilities can be detected using HPC differences between patched and unpatched library versions. Further, we demonstrate that standardised cryptographic functions within ARM TrustZone TEE applications can be recognised using non-secure world HPC measurements, applying to platforms that insecurely perturb the performance monitoring unit (PMU) during TEE execution. High accuracy was achieved in all cases (86.22–99.83%) depending on the application, architectural, and compilation assumptions. Lastly, we discuss mitigations, outstanding challenges, and directions for future research.

End-to-End Security for Distributed Event-driven Enclave Applications on Heterogeneous TEEs

This article presents an approach to provide strong assurance of the secure execution of distributed event-driven applications on shared infrastructures, while relying on a small Trusted Computing Base. We build upon and extend security primitives provided by Trusted Execution Environments (TEEs) to guarantee authenticity and integrity properties of applications, and to secure control of input and output devices. More specifically, we guarantee that if an output is produced by the application, it was allowed to be produced by the application’s source code based on an authentic trace of inputs. We present an integrated open-source framework to develop, deploy, and use such applications across heterogeneous TEEs. Beyond authenticity and integrity, our framework optionally provides confidentiality and a notion of availability, and facilitates software development at a high level of abstraction over the platform-specific TEE layer. We support event-driven programming to develop distributed enclave applications in Rust and C for heterogeneous TEE, including Intel SGX, ARM TrustZone, and Sancus. In this article we discuss the workings of our approach, the extensions we made to the Sancus processor, and the integration of our development model with commercial TEEs. Our evaluation of security and performance aspects show that TEEs, together with our programming model, form a basis for powerful security architectures for dependable systems in domains such as Industrial Control Systems and the Internet of Things, illustrating our framework’s unique suitability for a broad range of use cases which combine cloud processing, mobile and edge devices, and lightweight sensing and actuation.

Overview of System-Level Security Technologies based on ARM TrustZone

With the rapid development of embedded technology and the increasing complexity of system functionality, there is a growing need for a trusted computing environment to ensure the security, integrity, and reliability of sensitive information. Systems not only need to protect the security of sensitive application code but also ensure the isolation of their execution process to prevent attacks and data theft. Traditional system protection is achieved by using security mechanisms that run in the same address space and privilege level as the kernel. However, this approach is not sufficiently secure as attackers who compromise the kernel can also compromise these security mechanisms. To achieve true kernel and critical data protection, security mechanisms need to be isolated. Therefore, building a trusted isolation runtime environment in the system is crucial for system security. TrustZone technology, developed by ARM, is a system-level security isolation framework capable of defending against various potential attacks. this paper provides an overall overview of different security isolation technologies. By concentrating on the principles and characteristics of ARM TrustZone, the paper conducts an in-depth analysis of system security isolation technology based on TrustZone. Finally, considering the existing security issues in the field of trusted execution environments, the paper presents prospects for the future development of this technology.

A survey on the (in)security of trusted execution environments

As the number of security and privacy attacks continue to grow around the world, there is an ever increasing need to protect our personal devices. As a matter of fact, more and more manufactures are relying on Trusted Execution Environments (TEEs) to shield their devices. In particular, ARM TrustZone (TZ) is being widely used in numerous embedded devices, especially smartphones, and this technology is the basis for secure solutions both in industry and academia. However, as shown in this paper, TEE is not bullet-proof and it has been successfully attacked numerous times and in very different ways. To raise awareness among potential stakeholders interested in this technology, this paper provides an extensive analysis and categorization of existing vulnerabilities in TEEs and highlights the design flaws that led to them. The presented vulnerabilities, which are not only extracted from existing literature but also from publicly available exploits and databases, are accompanied by some effective countermeasures to reduce the likelihood of new attacks. The paper ends with some appealing challenges and open issues.

Retracted: An edge-computing based Industrial Gateway for Industry 4.0 using ARM TrustZone technology

Secure and efficient communication to establish a seamless nexus between the five levels of a typical automation pyramid is paramount to Industry 4.0. Specifically, vertical and horizontal integration of these levels is an overarching requirement to accelerate productivity and improve operational activities. Vertical integration can improve visibility, flexibility, and productivity by connecting systems and applications. Horizontal integration can provide better collaboration and adaptability by connecting internal production facilities, multi-site operations, and third-party partners in a supply chain. In this paper, we propose an Edge-computing based Industrial Gateway for interfacing information technology and operational technology that can enable Industry 4.0 vertical and horizontal integration. Subsequently, we design and develop a working prototype to demonstrate a remote production-line maintenance use case with a strong focus on security aspects and the edge paradigm to bring computational resources and data storage closer to data sources.

MA-TEECM: Mutual Anonymous Authentication-Based Credential Migration Technology for Mobile Trusted Execution Environments

ARM TrustZone is the most widely used mobile trusted execution environment (TEE) technology today. Its hardware-enabled isolated execution environment provides reliable assurance of secure storage of credentials in mobile devices. However, the research on managing credentials stored in the TEE throughout the lifecycle of mobile devices has received little attention in recent years, and the credentials in TEE generally face usability problems caused by the mobile device lifecycle events. Aiming at the risk of information disclosure caused by the third-party service providers in the traditional credential migration scheme, this paper presents a mutual anonymous authentication-based credential migration framework for mobile trusted execution environments. First, we propose a peer-to-peer credential migration model between mobile terminals based on TrustZone and SGX, which solves the single point of failure caused by attacks on trusted third parties that act as credential transfer stations and managers in traditional solutions; Second, we propose an identity authentication protocol between TEEs based on mutual anonymous authentication, and a detailed authentication process is designed based on the universal mobile TEE model; Third, we build a formal verification model using High-Level Protocol Specification Language (HLPSL). Finally, the formal and informal security analysis indicate that the improved scheme meets the expected security requirements and is secure against several known attacks.

A Survey of Trusted Computing Solutions Using FPGAs

Ensuring the security and privacy of computation and data management in the cloud and edge is an ever-important requirement. There are several working solutions today for trusted computing with general purpose processors, for instance, Intel SGX and ARM TrustZone. However, with the widespread commercial adoption of specialized hardware accelerators in the cloud and at the edge, most importantly FPGAs, two questions emerge: 1) How secure are they against threats? and 2) How could FPGAs be utilized for more efficient trusted computing? In this survey, we investigate these two questions precisely. Even though there have been numerous surveys in the past on the security of FPGAs, we believe it is timely to study the space of related work again, given the large number of data-centric applications aimed at targeting trusted execution environments that have recently appeared. Therefore, in addition to presenting an overview of state of the art, we also highlight some opportunities for FPGAs in the context of providing efficient trusted computation.

Data Covert Channels between the Secure World and the Normal World in the ARM TrustZone Architecture

Data Covert Channels between the Secure World and the Normal World in the ARM TrustZone Architecture

STBEAT: Software Update on Trusted Environment Based on ARM TrustZone

In recent years, since edge computing has become more and more popular, its security issues have become apparent and have received unprecedented attention. Thus, the current research concentrates on security not only regarding devices such as PCs, smartphones, tablets, and IoTs, but also the automobile industry. However, since attack vectors have become more sophisticated than ever, we cannot just protect the zone above the system software layer in a certain operating system, such as Linux, for example. In addition, the challenges in IoT devices, such as power consumption, performance efficiency, and authentication management, still need to be solved. Since most IoT devices are controlled remotely, the security regarding system maintenance and upgrades has become a big issue. Therefore, a mechanism that can maintain IoT devices within a trusted environment based on localhost or over-the-air (OTA) will be a viable solution. We propose a mechanism called STBEAT, integrating an open-source project with ARM TrustZone to solve the challenges of upgrading the IoT system and updating system files more safely. This paper focuses on the ARMv7 architecture and utilizes the security stack from TrustZone to OP-TEE under the STM32 board package, and finally obtains the security key from the trusted application, which is used to conduct the cryptographic operations and then install the newer image on the MMC interface. To sum up, we propose a novel software update strategy and integrated ARM TrustZone security extension to beef up the embedded ecosystem.

Cross-World Covert Channel on ARM Trustzone through PMU.

The TrustZone technology is incorporated in a majority of recent ARM Cortex A and Cortex M processors widely deployed in the IoT world. Security critical code execution inside a so-called secure world is isolated from the rest of the application execution within a normal world. It provides hardware-isolated area called a trusted execution environment (TEE) in the processor for sensitive data and code. This paper demonstrates a vulnerability in the secure world in the form of a cross-world, secure world to normal world, covert channel. Performance counters or Performance Monitoring Unit (PMU) events are used to convey the information from the secure world to the normal world. An encoding program generates appropriate PMU event footprint given a secret S. A corresponding decoding program reads the PMU footprint and infers S using machine learning (ML). The machine learning model can be trained entirely from the data collected from the PMU in user space. Lack of synchronization between PMU start and PMU read adds noise to the encoding/decoding ML models. In order to account for this noise, this study proposes three different synchronization capabilities between the client and trusted applications in the covert channel. These are synchronous, semi-synchronous, and asynchronous. Previously proposed PMU based covert channels deploy L1 and LLC cache PMU events. The latency of these events tends to be 100–1000 cycles limiting the bandwidth of these covert channels. We propose to use microarchitecture level events with latency of 10–100 cycles captured through PMU for covert channel encoding leading to a potential 100× higher bandwidth. This study conducts a series of experiments to evaluate the proposed covert channels under various synchronization models on a TrustZone supported Cortex-A processor using OP-TEE framework. As stated earlier, switch from signaling based on PMU cache events to PMU microarchitectural events leads to approximately 15× higher covert channel bandwidth. This proposed finer-grained microarchitecture event encoding covert channel can achieve throughput of the order of 11 Kbits/s as opposed to previous work’s throughput of the order of 760 bits/s.

Defending against OS-Level Malware in Mobile Devices via Real-Time Malware Detection and Storage Restoration

Combating the OS-level malware is a very challenging problem as this type of malware can compromise the operating system, obtaining the kernel privilege and subverting almost all the existing anti-malware tools. This work aims to address this problem in the context of mobile devices. As real-world malware is very heterogeneous, we narrow down the scope of our work by especially focusing on a special type of OS-level malware that always corrupts user data. We have designed mobiDOM, the first framework that can combat the OS-level data corruption malware for mobile computing devices. Our mobiDOM contains two components, a malware detector and a data repairer. The malware detector can securely and timely detect the presence of OS-level malware by fully utilizing the existing hardware features of a mobile device, namely, flash memory and Arm TrustZone. Specifically, we integrate the malware detection into the flash translation layer (FTL), a firmware layer embedded into the flash storage hardware, which is inaccessible to the OS; in addition, we run a trusted application in the Arm TrustZone secure world, which acts as a user-level manager of the malware detector. The FTL-based malware detection and the TrustZone-based manager can communicate with each other stealthily via steganography. The data repairer can allow restoring the external storage to a healthy historical state by taking advantage of the out-of-place-update feature of flash memory and our malware-aware garbage collection in the FTL. Security analysis and experimental evaluation on a real-world testbed confirm the effectiveness of mobiDOM.

PSpSys: A time-predictable mixed-criticality system architecture based on ARM TrustZone

In mixed-criticality systems, components often have different criticality requirements that must be met. Components with different criticality requirements must be partitioned into independent execution domains with robust inter-domain isolation, in order to prevent interference between domains of different criticality. For the most critical components, timing-predictability and performance/efficiency are key in ensuring the correct execution of critical components. Existing approaches achieve the required inter-domain isolation using either virtualisation technology or a hardware isolation environment. However, these approaches often conflict with the required timing-predictability and performance/efficiency of components with the highest criticality, which originates from (i) the introduction of complicated system architectures; (ii) the neglection of partitioning and multiplexing of I/Os; (iii) the lack of bounded worst-case timing. In this article, we propose a new mixed-criticality system architecture based on ARM TrustZone technology, termed P arallel Sp ace Sys tem ( PSpSys ), which is a timing-predictable system architecture with hardware-level isolation and predictable inter-domain shared I/O management. In addition, an alternative co-processor is also proposed for PSpSys , which significantly improves performance with reduced system complexity. PSpSys therefore can be applied to safety-critical mechatronic systems (e.g. unmanned autonomous systems, field robotics) which perform tasks on different critical levels. Finally, we demonstrate how PSpSys can be exploited to achieve all the required features in real hardware platform (Xilinx ZC706 evaluation board).

LEAP: TrustZone Based Developer-Friendly TEE for Intelligent Mobile Apps

ARM TrustZone is widely deployed on commercial-off-the-shelf mobile devices for secure execution. However, many Apps cannot enjoy this feature because it brings many constraints to App developers. Previous works have been proposed to build a secure execution environment for developers on top of TrustZone. Unfortunately, these works are still not fully-fledged solutions for mobile Apps, especially for emerging intelligent Apps. To this end, we propose LEAP, which is a lightweight developer-friendly TEE solution for mobile Apps. LEAP enables isolated codes to execute in parallel and access peripheral (e.g., mobile GPUs) with ease, flexibly manages system resources upon different workloads, and offers the auto DevOps tool to help developers prepare the codes running on it. We implement the LEAP prototype on the off-the-shelf ARM platform and conduct extensive experiments on it. The experimental results show that Apps can be adapted to run with LEAP easily and efficiently. Compared to the state-of-the-art work along this research line, LEAP can achieve an average 3.57x speedup in supporting intelligent Apps using mobile GPU acceleration.

TrustSAMP: Securing Streaming Music Against Multivector Attacks on ARM Platform

Streaming music has dominated the digital music industry in recent years, which allows users to enjoy a huge music library online with a low subscription price. Terminal-side audio DRM (Digital Right Management) is very critical for streaming music industry, compromising of which will cause unrestricted listening, dumping and unauthorized secondary distribution. However, existing DRM protection schemes mainly focus on defeating software attacks but lack complete shielding against the physical memory disclosure attacks, which may even be launched by the owner of the terminal device. In this paper, we propose a terminal-side audio DRM solution called TrustSAMP to protect the copyrighted audio data against both software attacks and physical memory disclosure attacks. The basic idea is to process the audio data plaintext only in certain on-SoC components secured by ARM TrustZone. To minimize the TCB (Trusted Computing Base) of the secure world, we separate the control flow and the data flow of the Linux audio subsystem and port only the codes used for audio data decryption and plaintext transfer into the secure world. Moreover, we leave most driver codes of the audio-associated on-SoC components in the rich OS (i.e., in the normal world), and introduce a tiny proxy in the secure world to control the associated registers according to the requests from the normal-world drivers. The prototype implemented on real hardware shows that TrustSAMP can play a variety of wav-format audio with very small overhead and negligible loss of audio quality.

ISotEE: A Hypervisor Middleware for IoT-Enabled Resource-Constrained Reliable Systems

Embedded systems for critical applications are often based on resource-constrained devices to meet the requirements like performance predictability and energy consumption. To deal with the increased software complexity, many of these systems have adopted reliable RTOSes (Real-Time Operating Systems) with advanced protection functionalities. Meanwhile, the concept of IoT (Internet of Things) is gaining momentum. Many IoT OSes, specialized to provide the large software stack required by IoT applications, have been released. Nevertheless, neither reliable RTOS nor IoT OS can satisfy all the requirements of IoT-enabled reliable systems. Dual-OS configuration (i.e. the coexistence of reliable RTOS and IoT OS) is a promising approach to achieve high reliability and productivity simultaneously. Existing dual-OS solutions, however, depend on additional hardware features (e.g. virtualization extensions, ARM TrustZone), which are unavailable in most resource-constrained devices. This paper presents iSotEE (iSolated Execution Environment), a middleware allowing IoT OS to run inside an isolated environment on top of a reliable RTOS without special hardware. Open-source implementations of iSotEE for Renesas RX (with TOPPERS/HRP3 as reliable RTOS, Amazon FreeRTOS as IoT OS) and ARMv7-M (with two configurations of Zephyr as reliable RTOS and IoT OS) architectures are provided and evaluated. The results show that iSotEE can create reliable systems with a small footprint for resource-constrained devices, high real-time performance for critical applications, and high productivity and throughput for IoT applications.