Round Optimal Black-Box “Commit-and-Prove”

Motivatedbytheoreticalandpracticalconsiderations,anim- portant line of research is to design secure computation protocols that only make black-box use of cryptography. An important component in nearly all the black-box secure computation constructions is a black- box commit-and-prove protocol. A commit-and-prove protocol allows a prover to commit to a value and prove a statement about this value while guaranteeing that the committed value remains hidden. A black- box commit-and-prove protocol implements this functionality while only making black-box use of cryptography. In this paper, we build several tools that enable constructions of round- optimal, black-box commit and prove protocols. In particular, assuming injective one-way functions, we design the first round-optimal, black- box commit-and-prove arguments of knowledge satisfying strong privacy against malicious verifiers, namely: – Zero-knowledge in four rounds and, – Witness indistinguishability in three rounds. Prior to our work, the best known black-box protocols achieving commit- and-prove required more rounds. We additionally ensure that our protocols can be used, if needed, in the delayed-input setting, where the statement to be proven is decided only towards the end of the interaction. We also observe simple applications of our protocols towards achieving black-box four-round constructions of extractable and equivocal commitments. We believe that our protocols will provide a useful tool enabling several new constructions and easy round-efficient conversions from non-black- box to black-box protocols in the future

14 3 3 protein masks the nuclear localization sequence of caspase 2

Caspase‐2 is an apical protease responsible for the proteolysis of cellular substrates directly involved in mediating apoptotic signaling cascades. Caspase‐2 activation is inhibited by phosphorylation followed by binding to the scaffolding protein 14‐3‐3, which recognizes two phosphoserines located in the linker between the caspase recruitment domain and the p19 domains of the caspase‐2 zymogen. However, the structural details of this interaction and the exact role of 14‐3‐3 in the regulation of caspase‐2 activation remain unclear. Moreover, the caspase‐2 region with both 14‐3‐3‐binding motifs also contains the nuclear localization sequence (NLS), thus suggesting that 14‐3‐3 binding may regulate the subcellular localization of caspase‐2. Here, we report a structural analysis of the 14‐3‐3ζ:caspase‐2 complex using a combined approach based on small angle X‐ray scattering, NMR, chemical cross‐linking, and fluorescence spectroscopy. The structural model proposed in this study suggests that phosphorylated caspase‐2 and 14‐3‐3ζ form a compact and rigid complex in which the p19 and the p12 domains of caspase‐2 are positioned within the central channel of the 14‐3‐3 dimer and stabilized through interactions with the C‐terminal helices of both 14‐3‐3ζ protomers. In this conformation, the surface of the p12 domain, which is involved in caspase‐2 activation by dimerization, is sterically occluded by the 14‐3‐3 dimer, thereby likely preventing caspase‐2 activation. In addition, 14‐3‐3 protein binding to caspase‐2 masks its NLS. Therefore, our results suggest that 14‐3‐3 protein binding to caspase‐2 may play a key role in regulating caspase‐2 activation

Feasibility and Completeness of Cryptographic Tasks in the Quantum World

htmlabstractIt is known that cryptographic feasibility results can change by moving from the classical to the quantum world. With this in mind, we study the feasibility of realizing functionalities in the framework of universal composability, with respect to both computational and information-theoretic security. With respect to computational security, we show that existing feasibility results carry over unchanged from the classical to the quantum world; a functionality is “trivial” (i.e., can be realized without setup) in the quantum world if and only if it is trivial in the classical world. The same holds with regard to functionalities that are complete (i.e., can be used to realize arbitrary other functionalities). In the information-theoretic setting, the quantum and classical worlds differ. In the quantum world, functionalities in the class we consider are either complete, trivial, or belong to a family of simultaneous-exchange functionalities (e.g., XOR). However, other results in the information-theoretic setting remain roughly unchanged