Une classification des hypothèses calculatoire dans le modèle du groupe algébrique

International audiencea We give a taxonomy of computational assumptions in the algebraic group model (AGM). We first analyze Boyen's Uber assumption family for bilinear groups and then extend it in several ways to cover assumptions as diverse as Gap Diffie-Hellman and LRSW. We show that in the AGM every member of these families is implied by the q-discrete logarithm (DL) assumption, for some q that depends on the degrees of the polynomials defining the Uber assumption. Using the meta-reduction technique, we then separate (q + 1)-DL from q-DL, which yields a classification of all members of the extended Uber-assumption families. We finally show that there are strong assumptions, such as one-more DL, that provably fall outside our classification, by proving that they cannot be reduced from q-DL even in the AGM

Mutations in Protein-Binding Hot-Spots on the Hub Protein Smad3 Differentially Affect Its Protein Interactions and Smad3-Regulated Gene Expression

Hub proteins are connected through binding interactions to many other proteins. Smad3, a mediator of signal transduction induced by transforming growth factor beta (TGF-β), serves as a hub protein for over 50 protein-protein interactions. Different cellular responses mediated by Smad3 are the product of cell-type and context dependent Smad3-nucleated protein complexes acting in concert. Our hypothesis is that perturbation of this spectrum of protein complexes by mutation of single protein-binding hot-spots on Smad3 will have distinct consequences on Smad3-mediated responses.We mutated 28 amino acids on the surface of the Smad3 MH2 domain and identified 22 Smad3 variants with reduced binding to subsets of 17 Smad3-binding proteins including Smad4, SARA, Ski, Smurf2 and SIP1. Mutations defective in binding to Smad4, e.g., D408H, or defective in nucleocytoplasmic shuttling, e.g., W406A, were compromised in modulating the expression levels of a Smad3-dependent reporter gene or six endogenous Smad3-responsive genes: Mmp9, IL11, Tnfaip6, Fermt1, Olfm2 and Wnt11. However, the Smad3 mutants Y226A, Y297A, W326A, K341A, and E267A had distinct differences on TGF-β signaling. For example, K341A and Y226A both reduced the Smad3-mediated activation of the reporter gene by ∼50% but K341A only reduced the TGF-β inducibilty of Olfm2 in contrast to Y226A which reduced the TGF-β inducibility of all six endogenous genes as severely as the W406A mutation. E267A had increased protein binding but reduced TGF-β inducibility because it caused higher basal levels of expression. Y297A had increased TGF-β inducibility because it caused lower Smad3-induced basal levels of gene expression.Mutations in protein binding hot-spots on Smad3 reduced the binding to different subsets of interacting proteins and caused a range of quantitative changes in the expression of genes induced by Smad3. This approach should be useful for unraveling which Smad3 protein complexes are critical for specific biological responses

LNCS

For 1≤m≤n, we consider a natural m-out-of-n multi-instance scenario for a public-key encryption (PKE) scheme. An adversary, given n independent instances of PKE, wins if he breaks at least m out of the n instances. In this work, we are interested in the scaling factor of PKE schemes, SF, which measures how well the difficulty of breaking m out of the n instances scales in m. That is, a scaling factor SF=ℓ indicates that breaking m out of n instances is at least ℓ times more difficult than breaking one single instance. A PKE scheme with small scaling factor hence provides an ideal target for mass surveillance. In fact, the Logjam attack (CCS 2015) implicitly exploited, among other things, an almost constant scaling factor of ElGamal over finite fields (with shared group parameters). For Hashed ElGamal over elliptic curves, we use the generic group model to argue that the scaling factor depends on the scheme's granularity. In low granularity, meaning each public key contains its independent group parameter, the scheme has optimal scaling factor SF=m; In medium and high granularity, meaning all public keys share the same group parameter, the scheme still has a reasonable scaling factor SF=√m. Our findings underline that instantiating ElGamal over elliptic curves should be preferred to finite fields in a multi-instance scenario. As our main technical contribution, we derive new generic-group lower bounds of Ω(√(mp)) on the difficulty of solving both the m-out-of-n Gap Discrete Logarithm and the m-out-of-n Gap Computational Diffie-Hellman problem over groups of prime order p, extending a recent result by Yun (EUROCRYPT 2015). We establish the lower bound by studying the hardness of a related computational problem which we call the search-by-hypersurface problem

The Olympics and Japanese national identity: Multi-layered otherness in Tokyo 2016 and 2020

This paper is closed access until 30th October 2020.How are Japanese identity narratives constructed in the Tokyo 2016 campaign and the Tokyo 2020 bid and organisation? The earlier narratives of Tokyo 1940 and 1964 bids entailed invoking the Western Otherness to emphasise Japan’s Asian affinity while simultaneously emphasising Japan’s un-Asian characteristics, effectively employing dual Otherness to tell the story of Japanese Self. Tokyo’s position as a global city today means that Japanese Self is now constituted through multiple Otherness involving the West, Asia, as well as the primacy of Tokyo in opposition to the relative neglect of the periphery, constructing a more complex story of Otherness. There are concerns Tokyo is hoarding infrastructure investment ahead of Tokyo 2020, just as the regions affected by March 2011 disasters require capital infusion, fuelling a sense of Tokyo versus the rest. Hence, on top of the residual dual Otherness that can still be witnessed, Tokyo 2020 grafts another layer of Otherness, this time at the domestic level. In this article, I explore identity narratives by policy elites and opinion leaders to show the complex nature of multi-layered Otherness in the Tokyo 2016 and 2020 bidding and organisation

The Ski proto-oncogene regulates body composition and suppresses lipogenesis

Objective: The Ski gene regulates skeletal muscle differentiation in vitro and and in vivo. In the c-Ski overexpression mouse model there occurs marked skeletal muscle hypertrophy with decreased adipose tissue mass. In this study, we have investigated the underlying molecular mechanisms responsible for the increased skeletal muscle and decreased adipose tissue mass in the c-Ski mouse