arXiv subjects

Klaus Wehrle

Publications and source records attributed to Klaus Wehrle.

At least 37 records · Page 2Linked to original sources

arXiv2022

Scalable and Privacy-Focused Company-Centric Supply Chain Management

Blockchain technology promises to overcome trust and privacy concerns inherent to centralized information sharing. However, current decentralized supply chain management systems do either not meet privacy and scalability requirements or require a trustworthy consortium, which is challenging for increasingly dynamic supply chains with constantly changing participants. In this paper, we propose CCChain, a scalable and privacy-aware supply chain management system that stores all information locally to give companies complete sovereignty over who accesses their data. Still, tamper protection of all data through a permissionless blockchain enables on-demand tracking and tracing of products as well as reliable information sharing while affording the detection of data inconsistencies. Our evaluation confirms that CCChain offers superior scalability in comparison to alternatives while also enabling near real-time tracking and tracing for many, less complex products.

cs.CR↗

arXiv2022

BP-MAC: Fast Authentication for Short Messages

Resource-constrained devices increasingly rely on wireless communication for the reliable and low-latency transmission of short messages. However, especially the implementation of adequate integrity protection of time-critical messages places a significant burden on these devices. We address this issue by proposing BP-MAC, a fast and memory-efficient approach for computing message authentication codes based on the well-established Carter-Wegman construction. Our key idea is to offload resource-intensive computations to idle phases and thus save valuable time in latency-critical phases, i.e., when new data awaits processing. Therefore, BP-MAC leverages a universal hash function designed for the bitwise preprocessing of integrity protection to later only require a few XOR operations during the latency-critical phase. Our evaluation on embedded hardware shows that BP-MAC outperforms the state-of-the-art in terms of latency and memory overhead, notably for small messages, as required to adequately protect resource-constrained devices with stringent security and latency requirements.

cs.CR↗

arXiv2022

A False Sense of Security? Revisiting the State of Machine Learning-Based Industrial Intrusion Detection

Anomaly-based intrusion detection promises to detect novel or unknown attacks on industrial control systems by modeling expected system behavior and raising corresponding alarms for any deviations.As manually creating these behavioral models is tedious and error-prone, research focuses on machine learning to train them automatically, achieving detection rates upwards of 99%. However, these approaches are typically trained not only on benign traffic but also on attacks and then evaluated against the same type of attack used for training. Hence, their actual, real-world performance on unknown (not trained on) attacks remains unclear. In turn, the reported near-perfect detection rates of machine learning-based intrusion detection might create a false sense of security. To assess this situation and clarify the real potential of machine learning-based industrial intrusion detection, we develop an evaluation methodology and examine multiple approaches from literature for their performance on unknown attacks (excluded from training). Our results highlight an ineffectiveness in detecting unknown attacks, with detection rates dropping to between 3.2% and 14.7% for some types of attacks. Moving forward, we derive recommendations for further research on machine learning-based approaches to ensure clarity on their ability to detect unknown attacks.

cs.CR↗

arXiv2021

Collaboration is not Evil: A Systematic Look at Security Research for Industrial Use

Following the recent Internet of Things-induced trends on digitization in general, industrial applications will further evolve as well. With a focus on the domains of manufacturing and production, the Internet of Production pursues the vision of a digitized, globally interconnected, yet secure environment by establishing a distributed knowledge base. Background. As part of our collaborative research of advancing the scope of industrial applications through cybersecurity and privacy, we identified a set of common challenges and pitfalls that surface in such applied interdisciplinary collaborations. Aim. Our goal with this paper is to support researchers in the emerging field of cybersecurity in industrial settings by formalizing our experiences as reference for other research efforts, in industry and academia alike. Method. Based on our experience, we derived a process cycle of performing such interdisciplinary research, from the initial idea to the eventual dissemination and paper writing. This presented methodology strives to successfully bootstrap further research and to encourage further work in this emerging area. Results. Apart from our newly proposed process cycle, we report on our experiences and conduct a case study applying this methodology, raising awareness for challenges in cybersecurity research for industrial applications. We further detail the interplay between our process cycle and the data lifecycle in applied research data management. Finally, we augment our discussion with an industrial as well as an academic view on this research area and highlight that both areas still have to overcome significant challenges to sustainably and securely advance industrial applications. Conclusions. With our proposed process cycle for interdisciplinary research in the intersection of cybersecurity and industrial application, we provide a foundation for further research.

cs.CR↗

arXiv2021

Tracking the QUIC Spin Bit on Tofino

QUIC offers security and privacy for modern web traffic by closely integrating encryption into its transport functionality. In this process, it hides transport layer information often used for network monitoring, thus obsoleting traditional measurement concepts. To still enable passive RTT estimations, QUIC introduces a dedicated measurement bit - the spin bit. While simple in its design, tracking the spin bit at line-rate can become challenging for software-based solutions. Dedicated hardware trackers are also unsuitable as the spin bit is not invariant and can change in the future. Thus, this paper investigates whether P4-programmable hardware, such as the Intel Tofino, can effectively track the spin bit at line-rate. We find that the core functionality of the spin bit can be realized easily, and our prototype has an accuracy close to software-based trackers. Our prototype further protects against faulty measurements caused by reordering and prepares the data according to the needs of network operators, e.g., by classifying samples into pre-defined RTT classes. Still, distinct concepts in QUIC, such as its connection ID, are challenging with current hardware capabilities.

cs.NI↗

arXiv2021

CoinPrune: Shrinking Bitcoin's Blockchain Retrospectively

Popular cryptocurrencies continue to face serious scalability issues due to their ever-growing blockchains. Thus, modern blockchain designs began to prune old blocks and rely on recent snapshots for their bootstrapping processes instead. Unfortunately, established systems are often considered incapable of adopting these improvements. In this work, we present CoinPrune, our block-pruning scheme with full Bitcoin compatibility, to revise this popular belief. CoinPrune bootstraps joining nodes via snapshots that are periodically created from Bitcoin's set of unspent transaction outputs (UTXO set). Our scheme establishes trust in these snapshots by relying on CoinPrune-supporting miners to mutually reaffirm a snapshot's correctness on the blockchain. This way, snapshots remain trustworthy even if adversaries attempt to tamper with them. Our scheme maintains its retrospective deployability by relying on positive feedback only, i.e., blocks containing invalid reaffirmations are not rejected, but invalid reaffirmations are outpaced by the benign ones created by an honest majority among CoinPrune-supporting miners. Already today, CoinPrune reduces the storage requirements for Bitcoin nodes by two orders of magnitude, as joining nodes need to fetch and process only 6 GiB instead of 271 GiB of data in our evaluation, reducing the synchronization time of powerful devices from currently 7 h to 51 min, with even larger potential drops for less powerful devices. CoinPrune is further aware of higher-level application data, i.e., it conserves otherwise pruned application data and allows nodes to obfuscate objectionable and potentially illegal blockchain content from their UTXO set and the snapshots they distribute.

cs.CR↗

arXiv2021

Challenges and Opportunities in Securing the Industrial Internet of Things

Given the tremendous success of the Internet of Things in interconnecting consumer devices, we observe a natural trend to likewise interconnect devices in industrial settings, referred to as Industrial Internet of Things or Industry 4.0. While this coupling of industrial components provides many benefits, it also introduces serious security challenges. Although sharing many similarities with the consumer Internet of Things, securing the Industrial Internet of Things introduces its own challenges but also opportunities, mainly resulting from a longer lifetime of components and a larger scale of networks. In this paper, we identify the unique security goals and challenges of the Industrial Internet of Things, which, unlike consumer deployments, mainly follow from safety and productivity requirements. To address these security goals and challenges, we provide a comprehensive survey of research efforts to secure the Industrial Internet of Things, discuss their applicability, and analyze their security benefits.

cs.CR↗

arXiv2021

Sharding and HTTP/2 Connection Reuse Revisited: Why Are There Still Redundant Connections?

HTTP/2 and HTTP/3 avoid concurrent connections but instead multiplex requests over a single connection. Besides enabling new features, this reduces overhead and enables fair bandwidth sharing. Redundant connections should hence be a story of the past with HTTP/2. However, they still exist, potentially hindering innovation and performance. Thus, we measure their spread and analyze their causes in this paper. We find that 36% - 72% of the 6.24M HTTP Archive and 78% of the Alexa Top 100k websites cause Chromium-based webbrowsers to open superfluous connections. We mainly attribute these to domain sharding, despite HTTP/2 efforts to revert it, and DNS load balancing, but also the Fetch Standard.

cs.NI↗

arXiv2021

Video Conferencing and Flow-Rate Fairness: A First Look at Zoom and the Impact of Flow-Queuing AQM

Congestion control is essential for the stability of the Internet and the corresponding algorithms are commonly evaluated for interoperability based on flow-rate fairness. In contrast, video conferencing software such as Zoom uses custom congestion control algorithms whose fairness behavior is mostly unknown. Aggravatingly, video conferencing has recently seen a drastic increase in use - partly caused by the COVID-19 pandemic - and could hence negatively affect how available Internet resources are shared. In this paper, we thus investigate the flow-rate fairness of video conferencing congestion control at the example of Zoom and influences of deploying AQM. We find that Zoom is slow to react to bandwidth changes and uses two to three times the bandwidth of TCP in low-bandwidth scenarios. Moreover, also when competing with delay aware congestion control such as BBR, we see high queuing delays. AQM reduces these queuing delays and can equalize the bandwidth use when used with flow-queuing. However, it then introduces high packet loss for Zoom, leaving the question how delay and loss affect Zoom's QoE. We hence show a preliminary user study in the appendix which indicates that the QoE is at least not improved and should be studied further.

cs.NI↗

arXiv2021

L, Q, R, and T -- Which Spin Bit Cousin Is Here to Stay?

Network operators utilize traffic monitoring to locate and fix faults or performance bottlenecks. This often relies on intrinsic protocol semantics, e.g., sequence numbers, that many protocols share implicitly through their packet headers. The arrival of (almost) fully encrypted transport protocols, such as QUIC, significantly complicates this monitoring as header data is no longer visible to passive observers. Recognizing this challenge, QUIC offers explicit measurement semantics by exposing the spin bit to measure a flow's RTT. Ongoing efforts in the IETF IPPM working group argue to expose further information and enable the passive quantification of packet loss. This work implements and evaluates four currently proposed measurement techniques (L-, Q-, R-, and T-bit). We find that all techniques generally provide accurate loss estimations, but that longer algorithmic intervals for Q and R, yet foremost for T, complicate detecting very small loss rates or loss on short connections. Deployment combinations of Q & R as well as Q & L, thus, have the best potential for accurately grasping the loss in networks.

cs.NI↗

arXiv2020

A novel receiver design for energy packet-based dispatching

A steadily growing share of renewable energies with uctuating and decentralized generation as well as rising peak loads require novel solutions to ensure the reliability of electricity supply. More speci cally, grid stability is endangered by equally relevant line constraints and battery capacity limits. In this light, energy packet-based dispatching with power signal dual modulation has recently been introduced as an innovative solution. However, this approach assumes a central synchronicity provision unit for energy packet dispatching. In order to overcome this assumption, the present paper's main contribution is a design of an energy packet receiver which recovers the required synchronicity information directly from the received signal itself. Key implementation aspects are discussed in detail. By means of a DC grid example, simulation results show the performance and applicability of the proposed novel receiver for packet-based energy dispatching.

eess.SP↗

arXiv2020

Easing the Conscience with OPC UA: An Internet-Wide Study on Insecure Deployments

Due to increasing digitalization, formerly isolated industrial networks, e.g., for factory and process automation, move closer and closer to the Internet, mandating secure communication. However, securely setting up OPC UA, the prime candidate for secure industrial communication, is challenging due to a large variety of insecure options. To study whether Internet-facing OPC UA appliances are configured securely, we actively scan the IPv4 address space for publicly reachable OPC UA systems and assess the security of their configurations. We observe problematic security configurations such as missing access control (on 24% of hosts), disabled security functionality (24%), or use of deprecated cryptographic primitives (25%) on in total 92% of the reachable deployments. Furthermore, we discover several hundred devices in multiple autonomous systems sharing the same security certificate, opening the door for impersonation attacks. Overall, in this paper, we highlight commonly found security misconfigurations and underline the importance of appropriate configuration for security-featuring protocols.

cs.CR↗

arXiv2020

Symbolic Partial-Order Execution for Testing Multi-Threaded Programs

We describe a technique for systematic testing of multi-threaded programs. We combine Quasi-Optimal Partial-Order Reduction, a state-of-the-art technique that tackles path explosion due to interleaving non-determinism, with symbolic execution to handle data non-determinism. Our technique iteratively and exhaustively finds all executions of the program. It represents program executions using partial orders and finds the next execution using an underlying unfolding semantics. We avoid the exploration of redundant program traces using cutoff events. We implemented our technique as an extension of KLEE and evaluated it on a set of large multi-threaded C programs. Our experiments found several previously undiscovered bugs and undefined behaviors in memcached and GNU sort, showing that the new method is capable of finding bugs in industrial-size benchmarks.

cs.PL↗

arXiv2020

Complying with Data Handling Requirements in Cloud Storage Systems

In past years, cloud storage systems saw an enormous rise in usage. However, despite their popularity and importance as underlying infrastructure for more complex cloud services, today's cloud storage systems do not account for compliance with regulatory, organizational, or contractual data handling requirements by design. Since legislation increasingly responds to rising data protection and privacy concerns, complying with data handling requirements becomes a crucial property for cloud storage systems. We present PRADA, a practical approach to account for compliance with data handling requirements in key-value based cloud storage systems. To achieve this goal, PRADA introduces a transparent data handling layer, which empowers clients to request specific data handling requirements and enables operators of cloud storage systems to comply with them. We implement PRADA on top of the distributed database Cassandra and show in our evaluation that complying with data handling requirements in cloud storage systems is practical in real-world cloud deployments as used for microblogging, data sharing in the Internet of Things, and distributed email storage.

cs.NI↗

arXiv2020

Utilizing Public Blockchains for the Sybil-Resistant Bootstrapping of Distributed Anonymity Services

Distributed anonymity services, such as onion routing networks or cryptocurrency tumblers, promise privacy protection without trusted third parties. While the security of these services is often well-researched, security implications of their required bootstrapping processes are usually neglected: Users either jointly conduct the anonymization themselves, or they need to rely on a set of non-colluding privacy peers. However, the typically small number of privacy peers enable single adversaries to mimic distributed services. We thus present AnonBoot, a Sybil-resistant medium to securely bootstrap distributed anonymity services via public blockchains. AnonBoot enforces that peers periodically create a small proof of work to refresh their eligibility for providing secure anonymity services. A pseudo-random, locally replicable bootstrapping process using on-chain entropy then prevents biasing the election of eligible peers. Our evaluation using Bitcoin as AnonBoot's underlying blockchain shows its feasibility to maintain a trustworthy repository of 1000 peers with only a small storage footprint while supporting arbitrarily large user bases on top of most blockchains.

cs.CR↗

arXiv2020

How to Securely Prune Bitcoin's Blockchain

Bitcoin was the first successful decentralized cryptocurrency and remains the most popular of its kind to this day. Despite the benefits of its blockchain, Bitcoin still faces serious scalability issues, most importantly its ever-increasing blockchain size. While alternative designs introduced schemes to periodically create snapshots and thereafter prune older blocks, already-deployed systems such as Bitcoin are often considered incapable of adopting corresponding approaches. In this work, we revise this popular belief and present CoinPrune, a snapshot-based pruning scheme that is fully compatible with Bitcoin. CoinPrune can be deployed through an opt-in velvet fork, i.e., without impeding the established Bitcoin network. By requiring miners to publicly announce and jointly reaffirm recent snapshots on the blockchain, CoinPrune establishes trust into the snapshots' correctness even in the presence of powerful adversaries. Our evaluation shows that CoinPrune reduces the storage requirements of Bitcoin already by two orders of magnitude today, with further relative savings as the blockchain grows. In our experiments, nodes only have to fetch and process 5 GiB instead of 230 GiB of data when joining the network, reducing the synchronization time on powerful devices from currently 5 h to 46 min, with even more savings for less powerful devices.

cs.CR↗

arXiv2019

Putting Privacy into Perspective -- Comparing Technical, Legal, and Users' View of Data Sensitivity

Web 2.0, social media, cloud computing, and IoT easily connect people around the globe, overcoming time and space barriers, and offering manifold benefits. However, the technological advances and increased user participation generate novel challenges for protecting users' privacy. From the user perspective, data disclosure depends, in part, on the perceived sensitivity of that data, and thus on a risk assessment of data disclosure. But in light of the new technological opportunities to process and combine data, it is questionable whether users are able to adequately evaluate the risks of data disclosures. As mediating authority, data protection laws try to protect user data, granting enhanced protection to 'special categories' of data. In this publication, the legal, technological, and user perspectives on data sensitivity are presented and compared. From a technological perspective, all data can be referred to as 'potentially sensitive.' The legal and user perspective on data sensitivity deviate as some data types are granted special protection by the law but are not perceived as very sensitive by the users, and vice versa. Merging the three perspectives, the implications for informational self-determination are discussed.

cs.CY↗

arXiv2019

Perceiving QUIC: Do Users Notice or Even Care?

QUIC, as the foundation for HTTP/3, is becoming an Internet reality. A plethora of studies already show that QUIC excels beyond TCP+TLS+HTTP/2. Yet, these studies compare a highly optimized QUIC Web stack against an unoptimized TCP-based stack. In this paper, we bring TCP up to speed to perform an eye-level comparison. Instead of relying on technical metrics, we perform two extensive user studies to investigate QUIC's impact on the quality of experience. First, we investigate if users can distinguish two protocol versions in a direct comparison, and we find that QUIC is indeed rated faster than TCP and even a tuned TCP. Yet, our second study shows that this perceived performance increase does mostly not matter to the users, and they rate QUIC and TCP indistinguishable.

cs.NI↗