Continuous NMC Secure Against Permutations and Overwrites, with Applications to CCA Secure Commitments

Non-Malleable Codes (NMC) were introduced by Dziembowski, Pietrzak and Wichs in ICS 2010 as a relaxation of error correcting codes and error detecting codes. Faust, Mukherjee, Nielsen, and Venturi in TCC 2014 introduced an even stronger notion of non-malleable codes called continuous non-malleable codes where security is achieved against continuous tampering of a single codeword without re-encoding. We construct information theoretically secure CNMC resilient to bit permutations and overwrites, this is the first Continuous NMC constructed outside of the split-state model. In this work we also study relations between the CNMC and parallel CCA commitments. We show that the CNMC can be used to bootstrap a self-destruct parallel CCA bit commitment to a self-destruct parallel CCA string commitment, where self-destruct parallel CCA is a weak form of parallel CCA security. Then we can get rid of the self-destruct limitation obtaining a parallel CCA commitment, requiring only one-way functions

A Unified and Composable Take on Ratcheting

Ratcheting, an umbrella term for certain techniques for achieving secure messaging with strong guarantees, has spurred much interest in the cryptographic community, with several novel protocols proposed as of lately. Most of them are composed from several sub-protocols, often sharing similar ideas across different protocols. Thus, one could hope to reuse the sub-protocols to build new protocols achieving different security, efficiency, and usability trade-offs. This is especially desirable in view of the community\u27s current aim for group messaging, which has a significantly larger design space. However, the underlying ideas are usually not made explicit, but rather implicitly encoded in a (fairly complex) security game, primarily targeted at the overall security proof. This not only hinders modular protocol design, but also makes the suitability of a protocol for a particular application difficult to assess. In this work we demonstrate that ratcheting components can be modeled in a composable framework, allowing for their reuse in a modular fashion. To this end, we first propose an extension of the Constructive Cryptography framework by so-called global event histories, to allow for a clean modularization even if the component modules are not fully independent but actually subtly intertwined, as in most ratcheting protocols. Second, we model a unified, flexibly instantiable type of strong security statement for secure messaging within that framework. Third, we show that one can phrase strong guarantees for a number of sub-protocols from the existing literature in this model with only minor modifications, slightly stronger assumptions, and reasonably intuitive formalizations. When expressing existing protocols\u27 guarantees in a simulation-based framework, one has to address the so-called commitment problem. We do so by reflecting the removal of access to certain oracles under specific conditions, appearing in game-based security definitions, in the real world of our composable statements. We also propose a novel non-committing protocol for settings where the number of messages a party can send before receiving a reply is bounded

Non-Interactive Non-Malleability from Quantum Supremacy

We construct non-interactive non-malleable commitments without setup in the plain model, under well-studied assumptions. First, we construct non-interactive non-malleable commitments with respect to commitment for $\epsilon \log \log n$ tags for a small constant $\epsilon > 0$, under the following assumptions: - Sub-exponential hardness of factoring or discrete log. - Quantum sub-exponential hardness of learning with errors (LWE). Second, as our key technical contribution, we introduce a new tag amplification technique. We show how to convert any non-interactive non-malleable commitment with respect to commitment for $\epsilon\log \log n$ tags (for any constant $\epsilon>0$) into a non-interactive non-malleable commitment with respect to replacement for $2^n$ tags. This part only assumes the existence of sub-exponentially secure non-interactive witness indistinguishable (NIWI) proofs, which can be based on sub-exponential security of the decisional linear assumption. Interestingly, for the tag amplification technique, we crucially rely on the leakage lemma due to Gentry and Wichs (STOC 2011). For the construction of non-malleable commitments for $\epsilon \log \log n$ tags, we rely on quantum supremacy. This use of quantum supremacy in classical cryptography is novel, and we believe it will have future applications. We provide one such application to two-message witness indistinguishable (WI) arguments from (quantum) polynomial hardness assumptions

Physical Activity: A Comparison of Rural And Urban Older Adults' Needs and Preferences

Physical activity (PA) rates among older adults are low. We examined and compared the PA needs, preferences, and practices of 118 rural- and urban-residing older adults through focus groups and surveys. The sample was diverse (White = 42.4%, Black = 37.3%), mostly female, food-secure, and not meeting PA recommendations (38.1%). PA rates were lower for rural-residing older adults (p This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License

Overcoming Impossibility Results in Composable Security using Interval-Wise Guarantees

Composable security definitions, at times called simulation-based definitions, provide strong security guarantees that hold in any context. However, they are also met with some skepticism due to many impossibility results; goals such as commitments and zero-knowledge that are achievable in a stand-alone sense were shown to be unachievable composably (without a setup) since provably no efficient simulator exists. In particular, in the context of adaptive security, the so-called simulator commitment problem arises: once a party gets corrupted, an efficient simulator is unable to be consistent with its pre-corruption outputs. A natural question is whether such impossibility results are unavoidable or only artifacts of frameworks being too restrictive. In this work, we propose a novel type of composable security statement that evades the commitment problem. Our new type is able to express the composable guarantees of schemes that previously did not have a clear composable understanding. To this end, we leverage the concept of system specifications in the Constructive Cryptography framework, capturing the conjunction of several interval-wise guarantees, each specifying the guarantees between two events. We develop the required theory and present the corresponding new composition theorem. We present three applications of our theory. First, we show in the context of symmetric encryption with adaptive corruption how our notion naturally captures the expected confidentiality guarantee---the messages remain confidential until either party gets corrupted---and that it can be achieved by any standard semantically secure scheme (negating the need for non-committing encryption). Second, we present a composable formalization of (so far only known to be standalone secure) commitment protocols, which is instantiable without a trusted setup like a CRS. We show it to be sufficient for being used in coin tossing over the telephone, one of the early intuitive applications of commitments. Third, we reexamine a result by Hofheinz, Matt, and Maurer [Asiacrypt\u2715] implying that IND-ID-CPA security is not the right notion for identity-based encryption, unmasking this claim as an unnecessary framework artifact

A New Approach to Black-Box Concurrent Secure Computation

We consider the task of constructing concurrently composable protocols for general secure computation by making only black-box use of underlying cryptographic primitives. Existing approaches for this task first construct a black-box version of CCA-secure commitments which provide a strong form of concurrent security to the committed value(s). This strong form of security is then crucially used to construct higher level protocols such as concurrently secure OT/coin-tossing (and eventually all functionalities). This work explores a fresh approach. We first aim to construct a concurrently-secure OT protocol whose concurrent security is proven directly using concurrent simulation techniques; in particular, it does not rely on the usual ``non-polynomial oracles\u27\u27 of CCA-secure commitments. The notion of concurrent security we target is super-polynomial simulation (SPS). We show that such an OT protocol can be constructed from polynomial hardness assumptions in a black-box manner, and within a constant number of rounds. In fact, we only require the existence of (constant round) semi-honest OT and standard collision-resistant hash functions. Next, we show that such an OT protocol is sufficient to obtain SPS-secure (concurrent) multiparty computation (MPC) for general functionalities. This transformation does not require any additional assumptions; it also maintains the black-box nature as well as the constant round feature of the original OT protocol. Prior to our work, the only known black-box construction of constant-round concurrently composable MPC required stronger assumptions; namely, verifiable perfectly binding homomorphic commitment schemes and PKE with oblivious public-key generation

Urinary nitrate excretion in relation to murine macrophage activation. Influence of dietary L-arginine and oral NG-monomethyl-L-arginine.

Abstract Murine macrophage oxidation of L-arginine guanidino nitrogen to nitrite/nitrate yields an intermediate effector, possibly nitric oxide, with antimicrobial activity. Total body nitrogen oxidation metabolism (NOM) was measured in vivo by determining the urinary nitrate excretion of mice ingesting a chemically defined nitrite/nitrate-free diet. As reported previously, mycobacterial infection with bacillus Calmétte-Guerin led to a large increase in urinary nitrate excretion. This increase was temporally related to macrophage activation in vivo. The substrate for macrophage nitrogen oxidation metabolism in vitro, L-arginine, was deleted from the diet without ameliorating the urinary nitrate excretion response induced by BCG. This suggested that L-arginine was synthesized endogenously because there are no other known natural substrates for NOM. A competitive inhibitor of NOM, the L-arginine analog, NG-monomethyl-L-arginine was fed to mice in their drinking water. NG-monomethyl-L-arginine ingestion blocked both basal and bacillus Calmétte-Guerin-induced urinary nitrate excretion over a 2-4 week time span. These experimental conditions should prove useful for further investigation on the role of macrophage NOM in host defense against intracellular microorganisms.</jats:p