Secure Code Update for Embedded Devices via Proofs of Secure Erasure

Abstract. Remote attestation is the process of verifying internal state of a remote embedded device. It is an important component of many security protocols and applications. Although previously proposed re-mote attestation techniques assisted by specialized secure hardware are effective, they not yet viable for low-cost embedded devices. One no-table alternative is software-based attestation, that is both less costly and more efficient. However, recent results identified weaknesses in some proposed software-based methods, thus showing that security of remote software attestation remains a challenge. Inspired by these developments, this paper explores an approach that relies neither on secure hardware nor on tight timing constraints typi-cal of software-based technqiques. By taking advantage of the bounded memory/storage model of low-cost embedded devices and assuming a small amount of read-only memory (ROM), our approach involves a new primitive – Proofs of Secure Erasure (PoSE-s). We also show that, even though it is effective and provably secure, PoSE-based attestation is not cheap. However, it is particularly well-suited and practical for two other related tasks: secure code update and secure memory/storage erasure. We consider several flavors of PoSE-based protocols and demonstrate their feasibility in the context of existing commodity embedded devices.

PADS: Practical Attestation for Highly Dynamic Swarm Topologies

Remote attestation protocols are widely used to detect device configuration (e.g., software and/or data) compromise in Internet of Things (IoT) scenarios. Unfortunately, the performances of such protocols are unsatisfactory when dealing with thousands of smart devices. Recently, researchers are focusing on addressing this limitation. The approach is to run attestation in a collective way, with the goal of reducing computation and communication. Despite these advances, current solutions for attestation are still unsatisfactory because of their complex management and strict assumptions concerning the topology (e.g., being time invariant or maintaining a fixed topology). In this paper, we propose PADS, a secure, efficient, and practical protocol for attesting potentially large networks of smart devices with unstructured or dynamic topologies. PADS builds upon the recent concept of non-interactive attestation, by reducing the collective attestation problem into a minimum consensus one. We compare PADS with a state-of-the art collective attestation protocol and validate it by using realistic simulations that show practicality and efficiency. The results confirm the suitability of PADS for low-end devices, and highly unstructured networks.Comment: Submitted to ESORICS 201

Secure Remote Attestation

More than ten years ago, a devastating data substitution attack was shown to successfully compromise all previously proposed remote attestation techniques. In fact, the authors went further than simply attacking previously proposed methods: they called into question whether it is theoretically possible for remote attestation methods to exist in face of their attack. Subsequently, it has been shown that it is possible, by relying on self-modifying code. We show that it is possible to create remote attestation that is secure against all data substitution attacks, without relying on self-modifying code. Our proposed method relies on a construction of the checksum process that forces frequent L2 cache overflows if any data substitution attack takes place

LIRA-V:Lightweight Remote Attestation for Constrained RISC-V Devices

This paper presents LIRA-V, a lightweight system for performing remote attestation between constrained devices using the RISC-V architecture. We propose using read-only memory and the RISC-V Physical Memory Protection (PMP) primitive to build a trust anchor for remote attestation and secure channel creation. Moreover, we propose a bi-directional attestation protocol for trusted device-to-device communication, which is subjected to formal symbolic verification using Scyther. We present the design, implementation and evaluation of LIRA-V using an off-the-shelf {RISC-V} microcontroller and present performance results to demonstrate its suitability. To our knowledge, we present the first remote attestation mechanism suitable for constrained RISC-V devices, with applications to the Internet of Things (IoT) and Cyber Physical Systems (CPS).Comment: Accepted at IEEE SafeThings (in conjunction with IEEE Security & Privacy '21

ERASMUS: Efficient Remote Attestation via Self- Measurement for Unattended Settings

Remote attestation (RA) is a popular means of detecting malware in embedded and IoT devices. RA is usually realized as an interactive protocol, whereby a trusted party -- verifier -- measures integrity of a potentially compromised remote device -- prover. Early work focused on purely software-based and fully hardware-based techniques, neither of which is ideal for low-end devices. More recent results have yielded hybrid (SW/HW) security architectures comprised of a minimal set of features to support efficient and secure RA on low-end devices. All prior RA techniques require on-demand operation, i.e, RA is performed in real time. We identify some drawbacks of this general approach in the context of unattended devices: First, it fails to detect mobile malware that enters and leaves the prover between successive RA instances. Second, it requires the prover to engage in a potentially expensive (in terms of time and energy) computation, which can be harmful for critical or real-time devices. To address these drawbacks, we introduce the concept of self-measurement where a prover device periodically (and securely) measures and records its own software state, based on a pre-established schedule. A possibly untrusted verifier occasionally collects and verifies these measurements. We present the design of a concrete technique called ERASMUS : Efficient Remote Attestation via Self-Measurement for Unattended Settings, justify its features and evaluate its performance. In the process, we also define a new metric -- Quality of Attestation (QoA). We argue that ERASMUS is well-suited for time-sensitive and/or safety-critical applications that are not served well by on-demand RA. Finally, we show that ERASMUS is a promising stepping stone towards handling attestation of multiple devices (i.e., a group or swarm) with high mobility

Extending TLS with mutual attestation for platform integrity assurance

Normally, secure communication between client-server applications is established using secure channel technologies such as Transport Layer Security (TLS). TLS is cryptographic protocol which ensures secure transmission of data and authenticity of communication at each endpoint platform. However, the protocol does not provide any trustworthiness assurance of the involved endpoint. This paper incorporates remote attestation in the TLS key exchange protocol to solve this issue.The proposed embedded attestation extension in TLS protocol will provide assurance of sender's platforms integrity to receiver, and vice versa.The CA responsibility in TLS is replaced using own Trusted Certificate Authority (TCA) in our protocol. The credibility of the proposed protocol is studied to secure against replay attack and collusion attack. The proof is performed using AVISPA with High Level Protocol Specification (HLPSL) through Dolev-Yao intruder model implementation of the proposed protocol

Secure Remote Attestation for Safety-Critical Embedded and IoT Devices

In recent years, embedded and cyber-physical systems (CPS), under the guise of Internet-of-Things (IoT), have entered many aspects of daily life. Despite many benefits, this develop-ment also greatly expands the so-called attack surface and turns these newly computerizedgadgets into attractive attack targets. One key component in securing IoT devices is malwaredetection, which is typically attained with (secure) remote attestation. Remote attestationis a distinct security service that allows a trusted verifier to verify the internal state of aremote untrusted device. Remote attestation is especially relevant for low/medium-end em-bedded devices that are incapable of protecting themselves against malware infection. Assafety-critical IoT devices become commonplace, it is crucial for remote attestation not tointerfere with the device’s normal operations. In this dissertation, we identify major issues inreconciling remote attestation and safety-critical application needs. We show that existingattestation techniques require devices to perform uninterruptible (atomic) operations duringattestation. Such operations can be time-consuming and thus may be harmful to the device’ssafety-critical functionality. On the other hand, simply relaxing security requirements of re-mote attestation can lead to other vulnerabilities. To resolve this conflict, this dissertationpresents the design, implementation, and evaluation of several mitigation techniques. In par-ticular, we propose two light-weight techniques capable of providing interruptible attestationmodality. In contrast to traditional techniques, our proposed techniques allow interrupts tooccur during attestation while ensuring malware detection via shuffled memory traversals ormemory locking mechanisms. Another type of techniques pursued in this dissertation aimsto minimize the real-time computation overhead during attestation. We propose using peri-odic self-measurements to measure and record the device’s state, resulting in more flexiblescheduling of the attestation process and also in no real-time burden as part of its interactionwith verifier. This technique is particularly suitable for swarm settings with a potentiallylarge number of safety-critical devices. Finally, we develop a remote attestation HYDRAarchitecture, based on a formally verified component, and use it as a building block in ourproposed mitigation techniques. We believe that this architecture may be of independentinterest

Advanced Remote Attestation Protocols for Embedded Systems

Small integrated computers, so-called embedded systems, have become a ubiquitous and indispensable part of our lives. Every day, we interact with a multitude of embedded systems. They are, for instance, integrated in home appliances, cars, planes, medical devices, or industrial systems. In many of these applications, embedded systems process privacy-sensitive data or perform safety-critical operations. Therefore, it is of high importance to ensure their secure and safe operation. However, recent attacks and security evaluations have shown that embedded systems frequently lack security and can often be compromised and misused with little effort. A promising technique to face the increasing amount of attacks on embedded systems is remote attestation. It enables a third party to verify the integrity of a remote device. Using remote attestation, attacks can be effectively detected, which allows to quickly respond to them and thus minimize potential damage. Today, almost all servers, desktop PCs, and notebooks have the required hardware and software to perform remote attestation. By contrast, a secure and efficient attestation of embedded systems is considerably harder to achieve, as embedded systems have to encounter several additional challenges. In this thesis, we tackle three main challenges in the attestation of embedded systems. First, we address the issue that low-end embedded devices typically lack the required hardware to perform a secure remote attestation. We present an attestation protocol that requires only minimal secure hardware, which makes our protocol applicable to many existing low-end embedded devices while providing high security guarantees. We demonstrate the practicality of our protocol in two applications, namely, verifying code updates in mesh networks and ensuring the safety and security of embedded systems in road vehicles. Second, we target the efficient attestation of multiple embedded devices that are connected in challenging network conditions. Previous attestation protocols are inefficient or even inapplicable when devices are mobile or lack continuous connectivity. We propose an attestation protocol that particularly targets the efficient attestation of many devices in highly dynamic and disruptive networks. Third, we consider a more powerful adversary who is able to physically tamper with the hardware of embedded systems. Existing attestation protocols that address physical attacks suffer from limited scalability and robustness. We present two protocols that are capable of verifying the software integrity as well as the hardware integrity of embedded devices in an efficient and robust way. Whereas the first protocol is optimized towards scalability, the second protocol aims at robustness and is additionally suited to be applied in autonomous networks. In summary, this thesis contributes to enhancing the security, efficiency, robustness, and applicability of remote attestation for embedded systems