High Speed Consensus with Trusted Execution Environments

In recent years, Byzantine consensus algorithms have seen a surge in popularitywith the rise of Bitcoin and blockchain technology. A major problem that hampersadoption of existing consensus algorithms in blockchain scenarios is their scalability. There has been much research in the past years aiming to optimize thesealgorithms and increase their efficiency. For example, recent work has shown that voting rounds present in many classical algorithms can be made drastically more efficient by the use of message aggregation techniques. Another trend is towards the usage of trusted hardware to increase performance and lower resource requirementsof these algorithms. Trusted hardware enables algorithms to reduce the lower bound on the number of replicas from $3f+1$ to $2f+1$, where $f$ is the number of tolerated faults. Currently, all existing Byzantine consensus algorithms either use no trusted hardware at all, or assume that all replicas have access to the same trusted hardware. This leaves a gap in the design space, neglecting scenarios where only some machines have access to trusted hardware. In this work, we investigate the possibilities where only a subset of all replicas has access to trusted hardware. We introduce the SACBFT framework, consisting of two transformations that can be applied to existing Byzantine consensus protocols, increasing their efficiency by allowing them to make use of trusted hardware that exists in the system. We apply the framework to PBFT and RePBFT to produce SACPBFT and SACRePBFT respectively, and show how to apply the framework to other protocols. We also evaluate a proof-of-concept implementation of SACPBFT, showing that it can dramatically reduce network usage and increase performance even when only a single replica has access to trusted hardware

Foundations and Evolution of Modern Computing Paradigms: Cloud, IoT, Edge, and Fog

Article in Journa

rTLS: Secure and Efficient TLS Session Resumption for the Internet of Things

In recent years, the Transport Layer Security (TLS) protocol has enjoyed rapid growth as a security protocol for the Internet of Things (IoT). In its newest iteration, TLS 1.3, the Internet Engineering Task Force (IETF) has standardized a zero round-trip time (0-RTT) session resumption sub-protocol, allowing clients to already transmit application data in their first message to the server, provided they have shared session resumption details in a previous handshake. Since it is common for IoT devices to transmit periodic messages to a server, this 0-RTT protocol can help in reducing bandwidth overhead. Unfortunately, the sub-protocol has been designed for the Web and is susceptible to replay attacks. In our previous work, we adapted the 0-RTT protocol to strengthen it against replay attacks, while also reducing bandwidth overhead, thus making it more suitable for IoT applications. However, we did not include a formal security analysis of the protocol. In this work, we address this and provide a formal security analysis using OFMC. Further, we have included more accurate estimates on its performance, as well as making minor adjustments to the protocol itself to reduce implementation ambiguity and improve resilience

rTLS: Lightweight TLS Session Resumption for Constrained IoT Devices

ICICS 2020 - International Conference on Information and Communications Securit

Fogification of electric drives:An industrial use case

Publication in Conference proceedings/Worksho

Fault-tolerant Clock Synchronization using Precise Time Protocol Multi-Domain Aggregation

2021 IEEE 24th International Symposium on Real-Time Distributed Computing (ISORC

Quantification of indocyanine green near-infrared fluorescence bowel perfusion assessment in colorectal surgery

Background: Indocyanine green near-infrared fluorescence bowel perfusion assessment has shown its potential benefit in preventing anastomotic leakage. However, the surgeon's subjective visual interpretation of the fluorescence signal limits the validity and reproducibility of the technique. Therefore, this study aimed to identify objective quantified bowel perfusion patterns in patients undergoing colorectal surgery using a standardized imaging protocol. Method: A standardized fluorescence video was recorded. Postoperatively, the fluorescence videos were quantified by drawing contiguous region of interests (ROIs) on the bowel. For each ROI, a time-intensity curve was plotted from which perfusion parameters (n = 10) were derived and analyzed. Furthermore, the inter-observer agreement of the surgeon’s subjective interpretation of the fluorescence signal was assessed. Results: Twenty patients who underwent colorectal surgery were included in the study. Based on the quantified time-intensity curves, three different perfusion patterns were identified. Similar for both the ileum and colon, perfusion pattern 1 had a steep inflow that reached its peak fluorescence intensity rapidly, followed by a steep outflow. Perfusion pattern 2 had a relatively flat outflow slope immediately followed by its plateau phase. Perfusion pattern 3 only reached its peak fluorescence intensity after 3 min with a slow inflow gradient preceding it. The inter-observer agreement was poor-moderate (Intraclass Correlation Coefficient (ICC): 0.378, 95% CI 0.210–0.579). Conclusion: This study showed that quantification of bowel perfusion is a feasible method to differentiate between different perfusion patterns. In addition, the poor-moderate inter-observer agreement of the subjective interpretation of the fluorescence signal between surgeons emphasizes the need for objective quantification