BLOXY: Providing Transparent and Generic BFT-Based Ordering Services for Blockchains

With the wide-spread use of blockchain technology, Byzantine fault-tolerant (BFT) protocols are explored as a means to achieve consensus on which transactions should be processed next. BFT protocols are not a one-size-fits-all solution: they should be chosen according to the blockchain's use case, which can range from supply chain management to decentralised storage, requiring specialisation e.g. regarding throughput, latency, or level of decentralisation. Previously, consensus protocols were usually hardcoded into the blockchain infrastructure and could not be exchanged, therefore inhibiting flexible use of an otherwise generic blockchain infrastructure. Hyperledger Fabric claims to provide modular consensus and support for crash-fault and Byzantine fault tolerant protocols. However, integrating a BFT protocol has shown that Fabric's architecture is currently not well-suited for this fault model as it requires substantial changes and thereby breaks Fabric's modularity. This also has to be repeated for each integrated BFT protocol. In this paper, we present Bloxy, a blockchain-aware trusted proxy running on the replica that encapsulates all BFT client functionality. Bloxy enables transparent access to generic BFT frameworks and preserves Fabric's modularity even for the Byzantine fault model. It runs inside a trusted execution environment based on Intel's Software Guard Extensions. Bloxy offers blockchain-specific communication mechanisms as well as short-term block storage to handle crashes or disconnects to ensure that all nodes receive block updates. We implemented two Bloxy-based ordering services based on PBFT and the hybrid BFT protocol Hybster. Our evaluation shows that our approach increases throughput by up to 71% compared to directly integrated BFT protocols

Dicarbonyl­dichloridobis(trimethyl­phosphane)iron(II)–carbonyl­dichlorido­tris(trimethyl­phosphane)iron(II)–tetra­hydro­furan (1/1/2)

The asymmetric unit of the title crystal, [FeCl2(C3H9P)3(CO)]·[FeCl2(C3H9P)2(CO)2]·2C4H8O, contains half mol­ecules of the two closely related FeII complexes lying on mirror planes and a tetra­hydro­furan solvent mol­ecule, one C atom of which is disordered over two sets of sites with site occupancy factors 0.633 (9) and 0.367 (9). In both FeII complex mol­ecules, a distorted octa­hedral coordination geometry has been observed around the Fe atoms. Weak intermolecular C—H⋯O inter­actions are observed in the crystal structure

Diphenylamine-substituted osmanaphthalyne complexes: structural, bonding, and redox properties of unusual donor–bridge–acceptor systems

Diarylamine-substituted osmanaphthalyne complexes that feature two redox centers linked by the rigid skeleton of the metallacycle (C^C+), specifically, [OsCl2(PPh3)2{(C^C+)NAr2}][BF4 ] (Ar=Ph (1 a), p-MeOPh (1 b)) and their open-ring precursors [OsHCl2(PPh3)2{(CC(PPh3 +)= CHPh)NR2}][BF4 ] (Ar=Ph (2 a), p-MeOPh (2 b)), were successfully synthesized and characterized by 1 H, 13C, and 31P NMR spectroscopy, ESI-MS, and elemental analysis. The solid-state molecular structures of complexes 1 a and 2 a were ascertained by single-crystal X-ray diffraction. The OsC bond length in both complexes 1 a and 2 a fell within the range reported for similar osmanaphthalynes and osmium carbyne complexes, respectively. The structural parameters determined for complex 1 a, which were successfully reproduced by theoretical calculations, point to a p-delocalized metallacycle structure. The purple color of compounds 1 a and b was explained by the diarylamine!Os(metallacycle) chargetransfer absorption in the visible region. The neutral, oneelectron-oxidized and one-electron-reduced states of compounds 1 a, b, and a reference complex that lacked the diarylamine substituent, [OsCl2(PPh3)2{(C^C+)}][BF4] (1’), were investigated by cyclic and square-wave voltammetry, UV/Vis/NIR spectroelectrochemistry, and DFT calculations. The spin density in singly oxidized complexes [1 a]+ and [1 b]+ predominantly resided on the aminyl segment, with osmium involvement controlled by the diphenylamine substitution. Spin density in stable, singly-reduced [1’] was distributed mainly over the osmanaphthalyne metallacycle