Bit Security as Computational Cost for Winning Games with High Probability

We introduce a novel framework for quantifying the bit security of security games. Our notion is defined with an operational meaning that a $\lambda$-bit secure game requires a total computational cost of $2^\lambda$ for winning the game with high probability, e.g., 0.99. We define the bit security both for search-type and decision-type games. Since we identify that these two types of games should be structurally different, we treat them differently but define the bit security using the unified framework to guarantee the same operational interpretation. The key novelty of our notion of bit security is to employ two types of adversaries: inner adversary and outer adversary. While the inner adversary plays a ``usual\u27\u27 security game, the outer adversary invokes the inner adversary many times to amplify the winning probability for the security game. We find from our framework that the bit security for decision games can be characterized by the information measure called the Rényi divergence of order $1/2$ of the inner adversary. The conventional ``advantage,\u27\u27 defined as the probability of winning the game, characterizes our bit security for search-type games. We present several security reductions in our framework for justifying our notion of bit security. Many of our results quantitatively match the results for the bit security notion proposed by Micciancio and Walter in 2018. In this sense, our bit security strengthens the previous notion of bit security by adding an operational meaning. A difference from their work is that, in our framework, the Goldreich-Levin theorem gives an optimal reduction only for ``balanced\u27\u27 adversaries who output binary values in a balanced manner

Bit-Security Preserving Hardness Amplification

Hardness amplification is one of the important reduction techniques in cryptography, and it has been extensively studied in the literature. The standard XOR lemma known in the literature evaluates the hardness in terms of the probability of correct prediction; the hardness is amplified from mildly hard (close to $1$) to very hard $1/2 + \varepsilon$ by inducing $\varepsilon^2$ multiplicative decrease of the circuit size. Translating such a statement in terms of the bit-security framework introduced by Micciancio-Walter (EUROCRYPT 2018) and Watanabe-Yasunaga (ASIACRYPT 2021), it may cause the bit-security loss by the factor of $\log(1/\varepsilon)$. To resolve this issue, we derive a new variant of the XOR lemma in terms of the R\\u27enyi advantage, which directly characterizes the bit security. In the course of proving this result, we prove a new variant of the hardcore lemma in terms of the conditional squared advantage; our proof uses a boosting algorithm that may output the $\bot$ symbol in addition to $0$ and $1$, which may be of independent interest

Unified View for Notions of Bit Security

A theoretical framework of the bit security of cryptographic primitives/games was first introduced in a pioneering work by Micciancio and Walter (Eurocrypt 2018), and an alternative framework was introduced by the authors (Asiacrypt 2021). First, we observe that quantitative results in the latter framework are preserved even if adversaries are allowed to output the failure symbol. With this slight modification, we show that the notion of bit security in the latter framework is equivalent to that in the former framework up to constant bits. Also, we demonstrate that several existing notions of advantages can be captured in a unified way. Based on this equivalence, we show that the reduction algorithm of Hast (J. Cryptology, 2004) gives a tight reduction of the Goldreich-Levin hard-core predicate to the hardness of one-way functions. These two results resolved open problems that remained. Furthermore, in the latter framework, we show that all games we need to care about are decision games. Namely, for every search game G, there is the corresponding decision game G′ such that G has λ-bit security if and only if G′ has λ-bit security. The game G′ consists of the real and the ideal games, where attacks in the ideal game are never approved. Such games often appear in game-hopping security proofs. The result justifies such security proofs because they lose no security. Finally, we provide a distribution replacement theorem. Suppose a game using distribution Q in a black-box manner is λ-bit secure, and two distributions P and Q are computationally λ-bit secure indistinguishable. In that case, the game where Q is replaced by P is also λ-bit secure

Chip or Wafer -Small quantity fabrication

International audienceIn the academic research activities in the cleanroom, where mass production is rarely required or substrate to be processed is sometimes limited in size, devices are often fabricated using diced chips rather than wafers. However, such fabrication often struggles to maintain quality, in part because of inhomogeneity on the small chip and the different chip size among users, which requires process optimization for each. One possible solution is to standardize processing chips attached to or embedded in a dummy wafer

Experimental demonstration of position-controllable topological interface states in high-frequency Kitaev topological integrated circuits

Abstract Topological integrated circuits are integrated-circuit realizations of topological systems. Here we show an experimental demonstration by taking the case of the Kitaev topological superconductor model. An integrated-circuit implementation enables us to realize high resonant frequency as high as 13GHz. We explicitly observe the spatial profile of a topological edge state. In particular, the topological interface state between a topological segment and a trivial segment is the Majorana-like state. We construct a switchable structure in the integrated circuit, which enables us to control the position of a Majorana-like interface state arbitrarily along a chain. Our results contribute to the development of topological electronics with high frequency integrated circuits

Chip or Wafer -Small quantity fabrication

International audienceIn the academic research activities in the cleanroom, where mass production is rarely required or substrate to be processed is sometimes limited in size, devices are often fabricated using diced chips rather than wafers. However, such fabrication often struggles to maintain quality, in part because of inhomogeneity on the small chip and the different chip size among users, which requires process optimization for each. One possible solution is to standardize processing chips attached to or embedded in a dummy wafer

Micro Water Flow Measurement Using a Temperature-Compensated MEMS Piezoresistive Cantilever

In this study, we propose a microelectromechanical system (MEMS) force sensor for microflow measurements. The sensor is equipped with a flow sensing piezoresistive cantilever and a dummy piezoresistive cantilever, which acts as a temperature reference. Since the dummy cantilever is also in the form of a thin cantilever, the temperature environment of the dummy sensor is almost identical to that of the sensing cantilever. The temperature compensation effect was measured, and the piezoresistive cantilever was combined with a gasket jig to enable the direct implementation of the piezoresistive cantilever in a flow tube. The sensor device stably measured flow rates from 20 μL/s to 400 μL/s in a silicon tube with a 2-mm inner diameter without being disturbed by temperature fluctuations

Carrot Consumption Frequency Associated with Reduced BMI and Obesity through the SNP Intermediary rs4445711

It is unclear whether genetic interactions are involved in the association between vegetable intake and reduced body mass index (BMI) or obesity. We conducted a comprehensive search for single nucleotide polymorphisms (SNPs) which are associated with the interaction between vegetable intake frequency and BMI or obesity. We performed a genome-wide association analysis to evaluate the genetic interactions between self-reported intake of vegetables such as carrot, broccoli, spinach, other green vegetables (green pepper and green beans), pumpkin, and cabbage with BMI and obesity, which is defined as a BMI ≥ 25.0 kg/m2 in the Japanese population (n = 12,225). The mean BMI and prevalence of obesity was 23.9 ± 3.4 kg/m2 and 32.3% in men and 22.1 ± 3.8 kg/m2 and 17.3% in in women, respectively. A significant interaction was observed between rs4445711 and frequency of carrot intake on BMI (p = 4.5 × 10−8). This interaction was slightly attenuated after adjustment for age, sex, alcohol intake, smoking, physical activity and the frequency of total vegetable intake (p = 2.1 × 10−7). A significant interaction was also observed between rs4445711 and frequency of carrot intake on obesity (p = 2.5 × 10−8). No significant interactions that were the same as the interaction between frequency of carrot intake and rs4445711 were observed between the intake frequency of broccoli, spinach, other green vegetables, pumpkin or cabbage and BMI or obesity. The frequency of carrot consumption is implicated in reducing BMI by the intermediary of rs4445711. This novel genetic association may provide new clues to clarify the association between vegetable intake and BMI or obesity

High titers of infectious SARS-CoV-2 in corpses of patients with COVID-19

Objectives: The prolonged presence of infectious SARS-CoV-2 in deceased patients with COVID-19 has been reported. However, infectious virus titers have not been determined. Such information is important for public health, death investigation, and handling corpses. The aim of this study was to assess the level of SARS-CoV-2 infectivity in the corpses of patients with COVID-19. Methods: We collected 11 nasopharyngeal swabs and 19 lung tissue specimens from 11 autopsy cases with COVID-19 in 2021. We then investigated the viral genomic copy number by real-time reverse transcription-polymerase chain reaction and infectious titers by cell culture and virus isolation. Results: Infectious virus was present in six of 11 (55%) cases, four of 11 (36%) nasopharyngeal swabs, and nine of 19 (47%) lung specimens. The virus titers ranged from 6.00E + 01 plaque-forming units/ml to 2.09E + 06 plaque-forming units/g. In all cases in which an infectious virus was found, the time from death to discovery was within 1 day and the longest postmortem interval was 13 days. Conclusion: The corpses of patients with COVID-19 may have high titers of infectious virus after a long postmortem interval (up to 13 days). Therefore, appropriate infection control measures must be taken when handling corpses