The 32-bit Unix time, which is commonly used in computer systems, will overflow on 2038-01-19. Extending the format to 64 bit would allow to count seconds for 584 billion years but misses the opportunity to add features, such as sub-second precision or relative time encoding, which are useful for a universal datetime encoding.We propose and implement Flexpoch, a versatile 64-bit time encoding that is compatible with Unix time, has a high range of 21 thousand years, supports leap seconds and timezone offsets, and offers multiple precisions from 119 ns to millennia while being highly resource-efficient.

High-precision time synchronization is a vital prerequisite for many modern applications and technologies, including Smart Grids, Time-sensitive Networking (TSN), and 5G networks. Although the Precision Time Protocol (PTP) can accomplish this requirement in trusted environments, it becomes unreliable in the presence of specific cyber attacks. Mainly, time delay attacks pose the highest threat to the protocol, enabling attackers to diverge targeted clocks undetected. With the increasing danger of cyber attacks, especially against critical infrastructure, there is a great demand for effective countermeasures to secure both time synchronization and the applications that depend on it. However, current solutions are not sufficiently capable of mitigating sophisticated delay attacks. For example, they lack proper integration into the PTP protocol, scalability, or sound evaluation with the required microsecond-level accuracy. This work proposes an approach to detect and counteract delay attacks against PTP, which is based on cyclic path asymmetry measurements over redundant paths. We leverage Software-defined Networking (SDN) capabilities to dynamically find these redundant paths in arbitrary networks, recommend new links to increase the network’s security, and ensure deterministic routing. Furthermore, we show how path redundancy can be utilized to reveal and mitigate undesirable asymmetries on the synchronization path that cause the malicious clock divergence. Moreover, we propose PTPsec, a secure PTP protocol, and its implementation based on the latest IEEE 1588-2019 standard. With PTPsec, we advance the conventional PTP to support reliable delay attack detection and mitigation. We validate our approach in software simulations and on a hardware testbed, which includes an attacker capable of performing static and incremental delay attacks at a microsecond precision. Our experimental results show that the proposed approach is scalable, and all attack scenarios can be reliably detected and mitigated with minimal detection time.

The increasing digitalization in manufacturing and trends like the Industrial Metaverse drive the need for secure decentralized asset exchanges and industrial asset intellectual property (IP) rights protection. Utilizing distributed ledgers and non-fungible tokens (NFTs) linked by a hash enables the management and authentication of assets. However, challenges arise in authenticating the same asset’s different versions and file formats using a single hash.In this work, we propose a new NFT structure that allows binding multiple files existing in different file formats, representing the same digital asset by combining a Merkle Tree (MT) with a calculated Average Perceptual Hash (APH). While the MT proves bitwise integrity, the APH verifies functional integrity for asset authentication. We evaluate our approach for exchanging Printed Circuit Board (PCB) designs in a decentralized ecosystem by calculating unique PCB fingerprints and the APH. Our results show a robust identification and integrity verification of PCB designs depending on the manipulation type. Our approach for asset authentication is generalizable to all asset classes with an appropriate perceptual hash.

High-precision time synchronization is a vital prerequisite for many modern applications and technologies, including Smart Grids, Time-Sensitive Networking (TSN), and 5G networks. Although the Precision Time Protocol (PTP) can accomplish this requirement in trusted environments, it becomes unreliable in the presence of specific cyber attacks. Mainly, time delay attacks pose the highest threat to the protocol, enabling attackers to diverge targeted clocks undetected. With the increasing danger of cyber attacks, especially against critical infrastructure, there is a great demand for effective countermeasures to secure both time synchronization and the applications that depend on it. However, current solutions are not sufficiently capable of mitigating sophisticated delay attacks. For example, they lack proper integration into the PTP protocol, scalability, or sound evaluation with the required microsecond-level accuracy. This work proposes an approach to detect and counteract delay attacks against PTP based on cyclic path asymmetry measurements over redundant paths. For that, we provide a method to find redundant paths in arbitrary networks and show how this redundancy can be exploited to reveal and mitigate undesirable asymmetries on the synchronization path that cause the malicious clock divergence. Furthermore, we propose PTPsec, a secure PTP protocol and its implementation based on the latest IEEE 1588-2019 standard. With PTPsec, we advance the conventional PTP to support reliable delay attack detection and mitigation. We validate our approach on a hardware testbed, which includes an attacker capable of performing static and incremental delay attacks at a microsecond precision. Our experimental results show that all attack scenarios can be reliably detected and mitigated with minimal detection time.

International audience

The Publish/Subscribe (Pub/Sub) pattern is an attractive paradigm for supporting Vehicle to Cloud (V2C) communication. However, the security threats on confidentiality, integrity, and access control of the published data challenge the adoption of the Pub/Sub model. To address that, our paper proposes a secure policy-based Pub/Sub model for V2C communication, which allows to encrypt and control the access to messages published by vehicles. A vehicle encrypts messages with a symmetric key while saving the key in distributed shares on semi-honest services, called KeyStores, using the concept of secret sharing. The security policy, generated by the same vehicle, authorizes certain cloud services to obtain the shares from the KeyStores. Here, granting access rights takes place without violating the decoupling requirement of the Pub/Sub model. Experimental results show that, besides the end-to-end security protection, our proposed system introduces significantly less overhead (almost 70% less) than the state-of-the-art approach SSL when reestablishing connections, which is a common scenario in the V2C context due to unreliable network connection.

Hash-based signatures (HBS) are promising candidates for quantum-secure signatures on embedded IoT devices because they only use fast integer math, are well understood, produce small public keys, and offer many design parameters. However, HBS can only sign a limited amount of messages and produce - similar to most post-quantum schemes - large signatures of several kilo bytes.In this paper, we explore possibilities to reduce the size of the signatures by 1. improving the Winternitz One-Time Signature with a more efficient encoding and 2. offloading auxiliary data to a gateway.We show that for similar security and performance, our approach produces 2.6 % smaller signatures in general and up to 17.3 % smaller signatures for the sender compared to the related approaches LMS and XMSS. Furthermore, our open-source implementation allows a wider set of parameters that allows to tailor the scheme to the available resources of an embedded device, which is an important factor to overcome the security challenges in IoT.

Autonomous driving, vehicle platoons and smart traffic management will dramatically improve our transportation systems. In contrast to centralized approaches, which do not scale efficiently with the actual traffic load, a decentralized traffic management based on distributed consensus could provide a robust, fair and well-scaling solution for infrastructures of variable density. In this paper, we propose a distributed platoon management scheme, where platoon operations such as join or merge are decided by consensus over a Vehicular ad hoc network (VANET). Since conventional consensus protocols are not suitable for Cyber-Physical Systems (CPS) such as platoons, we introduce CUBA, a new validated and verifiable consensus protocol especially tailored to platoons, which considers their special communication topology. We demonstrate that CUBA only introduces a small communication overhead compared to the centralized, Leader-based approach and significantly outperforms related distributed approaches.

Smart contracts enable autonomous decentralized organizations (DADs) in large, trustless and open trading networks by specifying conditions for automated transactions of cryptographically secured data. This data could represent cryptocurrencies but also sensor data or commands to Cyber-Physical Systems (CPS) connected to the Internet. To provide reliability, the contract code is enforced by consensus and the transactions it triggers are nonrevertible, even if they were not intended by the programmer, which could lead to dangerous system behavior. In this paper, we conduct a survey over existing smart contract platforms and languages to determine requirements for the design of a safer contract language. Subsequently we propose concepts that enhance the understanding of code by limiting confusing language constructs, such as nesting, arbitrary naming of operations, and unreadable hash identifiers. This enables human reasoning about the contract semantics on a much higher abstraction layer, because a common understanding can be derived from the language specification itself. We implement these concepts in a new domain specific language called SmaCoNat to illustrate the feasibility and show that our concepts are barely covered by existing languages but significantly enhance readability and safety without violating deterministic parsability.

Blockchain provides decentralized consensus in large, open networks without a trusted authority, making it a promising solution for the Internet of Things (IoT) to distribute verifiable data, such as firmware updates. However, verifying data integrity and consensus on a linearly growing blockchain quickly exceeds memory and processing capabilities of embedded systems. As a remedy, we propose a generic blockchain extension that enables highly constrained devices to verify the inclusion and integrity of any block within a blockchain. Instead of traversing block by block, we construct a LeapChain that reduces verification steps without weakening the integrity guarantees of the blockchain. Applied to Proof-of-Work blockchains, our scheme can be used to verify consensus by proving a certain amount of work on top of a block. Our analytical and experimental results show that, compared to existing approaches, only LeapChain provides deterministic and tight upper bounds on the memory requirements in the kilobyte range, significantly extending the possibilities of blockchain application on embedded IoT devices.

In this paper, we present Smart2, an advanced smartphone charger that mitigates battery's capacity fading, which until now has usually been ignored. Smart2 exploits the fact that many users charge their phones over night. Since the overnight charging duration is unnecessarily long, the battery is subjected to a high average state of charge (SOC), which accelerates battery aging. Therefore, we delay the charging adaptively to be done shortly before the phone is unplugged. With this scheme, clearly when averaged over the duration of the night, the average SOC is lower and hence aging is reduced. Indicators are a set alarm clock and/or statistics of previous usage. Similarly, we lower the maximum target SOC. To enable this, the main challenges are firstly to find a solution that does not negatively influence the usability and secondly to quantify the achieved savings in terms of aging mitigation. Towards this, we propose a novel charging scheme which can be implemented in the smartphone's firmware. Furthermore, we propose a modified battery charging device that can be used with almost all existing smart phone models. Using our proposed techniques, the average battery cycle life can be nearly doubled from 3.7 to 6.6 years.