This paper introduces the Two-Class (r,k)-Coloring problem: Given a fixed number of k colors, such that only r of these k colors allow conflicts, what is the minimal number of conflicts incurred by an optimal coloring of the graph?

We establish that the family of Two-Class (r,k)-Coloring problems is NP-complete for any $k \geq 2$ when $(r, k) \neq (0,2)$. Furthermore, we show that Two-Class (r,k)-Coloring for $k \geq 2$ colors with one (r = 1) relaxed color cannot be approximated to any constant factor ($\notin$ APX).

Finally, we show that Two-Class (r,k)-Coloring with $k \geq r \geq 2$ colors is APX-complete.

We introduce FnF-BFT, a parallel-leader byzantine fault-tolerant state-machine replication protocol for the partially synchronous model with theoretical performance bounds during synchrony. By allowing all replicas to act as leaders and propose requests independently, FnF-BFT parallelizes the execution of requests. Leader parallelization distributes the load over the entire network – increasing throughput by overcoming the single-leader bottleneck. We further use historical data to ensure that well-performing replicas are in command. FnF-BFT's communication complexity is linear in the number of replicas during synchrony and thus competitive with state-of-the-art protocols. Finally, with FnF-BFT, we introduce the first BFT protocol with performance guarantees in stable network conditions under truly byzantine attacks. A prototype implementation of FnF-BFT outperforms (state-of-the-art) HotStuff's throughput, especially as replicas increase, showcasing FnF-BFT's significantly improved scaling capabilities.

Hyperloop pods are expected to travel faster than 1,000 km/h. Apart from high speed, high throughput and low latency are crucial to hyperloop's success. We show that hyperloop networks have the potential to transport as many passengers as train or plane networks. Our on-demand pod scheduling method provides low passenger waiting times of only a few minutes, even at peak times. That minimizes the overall trip latencies. Further, our scheduling results in low resource usage in terms of consumed energy and required number of pods in the system.

With on-demand scheduling, passengers need not look up schedules and cannot miss connections. Rather, the schedule follows passengers' itineraries. In addition, the hyperloop concept can enable many direct connections due to small pod capacities.

We conclude that hyperloop systems have the potential to become the preferred mode of transportation by being fast, reducing waiting times and keeping up with high demand -- all while offering more convenience than current public transportation.

PermitBFT establishes a permissioned byzantine ledger in the partially synchronous networking model. For n replicas, PermitBFT tolerates up to f < n/3 byzantine replicas. It is the first BFT protocol to achieve a latency of just 2 message delays despite tolerating byzantine replicas throughout the “fast track”, as long as they are not the leader. The design of PermitBFT relies on two fundamental concepts. First, in PermitBFT the participating nodes do not wait for a distinguished leader to act and subsequently confirm its actions, but send permits to the next leader proactively. Second, PermitBFT achieves a separation of the decision powers that are usually concentrated on a single leader node. A leader in PermitBFT controls which transactions to include in a new block, but not where to append the block in the block graph.