Kaikki aineistot
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Experimental and theoretical characterisation and studies of the stability of heterobicyclic thiazinium salts (bicyclic 2-mercaptoimidazolium chlorides and bromides) were performed to rationalise and understand the influence of the counterion (Cl−↔ Br−) and the replacement of CH by N on crystal packing, the influence of the anion on the moisture and temperature dependent stability, and the racemisation behaviour of the imidazo-thiazinium chloride. Six compounds were synthesised and for five of the compounds the structures were solved from single-crystal X-ray diffraction data. The structural features of the sixth compound could be derived from powder X-ray diffraction data comparisons. An exchange of the Cl−anion by Br−does not influence the crystal packing of the racemic thiazinium salt but increases its moisture dependent stability. In contrast, replacing the imidazole moiety of the cation by a triazole or tetrazole moiety results in distinct packing arrangements of the investigated bromide salts, although,substitution calculations suggest that isostructural packing arrangements might exist. The binary melting point phase diagram was constructed to confirm the nature of the racemic species of the thiazinium chloride, and differential scanning calorimetry and lattice energy minimisations were used to estimate the enthalpy difference between the racemic and enantiopure crystals, rationalising the high tendency of racemisation of the enantiopure compound.
We present a new method for transforming zero-knowledge protocols in the designated verifier setting into public-coin protocols, which can be made non-interactive and publicly verifiable. Our transformation applies to a large class of ZK protocols based on oblivious transfer. In particular, we show that it can be applied to recent, fast protocols based on vector oblivious linear evaluation (VOLE), with a technique we call VOLE-in-the-head, upgrading these protocols to support public verifiability. Our resulting ZK protocols have linear proof size, and are simpler, smaller and faster than related approaches based on MPC-in-the-head. To build VOLE-in-the-head while supporting both binary circuits and large finite fields, we develop several new technical tools. One of these is a new proof of security for the SoftSpokenOT protocol (Crypto 2022), which generalizes it to produce certain types of VOLE correlations over large fields. Secondly, we present a new ZK protocol that is tailored to take advantage of this form of VOLE, which leads to a publicly verifiable VOLE-in-the-head protocol with only 2x more communication than the best, designated-verifier VOLE-based protocols. We analyze the soundness of our approach when made non-interactive using the Fiat-Shamir transform, using round-by-round soundness. As an application of the resulting NIZK, we present FAEST, a post-quantum signature scheme based on AES. FAEST is the first AES-based signature scheme to be smaller than SPHINCS+, with signature sizes between 5.6 and 6.6kB at the 128-bit security level. Compared with the smallest version of SPHINCS+ (7.9kB), FAEST verification is slower, but the signing times are between 8x and 40x faster.
Expedient alkylations of 1-methyl-3H-imidazole-2-thione, a pharmaceutical active ingredient available in bulk quantities, provide high yield access to numerous protonated, or quaternized imidazoliums with chemospecific attachment of the fluoroponytail at the 2-mercapto functionality. The deprotonated primary target products represent valuable nitrogen heterocyclic bases, capable of further substitution, and salt or complex formation. Specific physicochemical characteristics that are relevant for phase and surface responsive behavior, e.g. critical micelle concentration, oleophobicity, depression of the aqueous surface tension, foam formation, emulsification of microgranular PTFE, are investigated for selected representatives and compared to the properties of common fluorosurfactants and ionic liquids. Remarkably, it is found that halogen bonding between iodide counterions of respective polyfluoroalkylmethimazolium systems and 1-iodoperfluoroalkanes, serving as the σ-hole partner of the halides, greatly affect the solubility profile of the resulting molecular adducts. Single-crystal X-ray structure determinations are carried out across the new fluorous substance classes. Strikingly, the helical arrangement of fluorine atoms along the chains typically encountered in polyfluorinated compounds is not found as the prevailing conformation. Rather, they are outnumbered by structural motifs exhibiting the rare zig-zag (linear alkane-like) chain conformation. Key derivatives are also subjected to preliminary ecotoxicological testing.