Compression Function Research Articles

Lower Bound on Number of Compression Calls of a Collision-Resistance Preserving Hash

The collision-resistant hash function is an early cryptographic primitive that finds extensive use in various applications. Remarkably, the Merkle-Damgård and Merkle tree hash structures possess the collision-resistance preserving property, meaning the hash function remains collision-resistant when the underlying compression function is collision-resistant. This raises the intriguing question of whether reducing the number of underlying compression function calls with the collision-resistance preserving property is possible. In pursuit of addressing these inquiries, we prove that for an ℓ n -to- s n -bit collision-resistance preserving hash function designed using r t n -to- n -bit compression function calls, we must have r ≥ ⌈ ( ℓ − s ) / ( t − 1 ) ⌉ . Throughout the paper, all operations other than the compression function are assumed to be linear (which we call linear hash mode).

Strict Avalanche Criterion of SHA-256 and Sub-Function-Removed Variants

The measure of diffusion, the property of dissipating patterns and statistical structures in cryptographic transformations, serves as a valuable heuristic for assessing the obscurity of patterns that could lead to collisions. As with many cryptographic hash functions, SHA-256 is thought to exhibit the property of diffusion. While SHA-256’s diffuse output is loosely documented, even less is known about how the diffusion rate changes across the 64 rounds in its compression function and how the algorithm’s individual sub-functions contribute to the overall diffusion. The diffusion of the unmodified compression function is initially measured using the Strict Avalanche Criterion (SAC), with the aim of understanding the alteration in diffusion across the 64 rounds of compression. The level to which sub-functions affect diffusion is subsequently measured, enabling potential prioritization of these sub-functions in future collision attacks. To accomplish this, the compression function is modified by removing sub-functions, and the diffusion of these new variants is measured. While the SAC measurements of each function eventually plateau close to the 50% target, no function, including the unmodified compression function, strictly meets the SAC, and multiple variant functions diffuse at comparatively slower rates.

Monolith: Circuit-Friendly Hash Functions with New Nonlinear Layers for Fast and Constant-Time Implementations

Hash functions are a crucial component in incrementally verifiable computation (IVC) protocols and applications. Among those, recursive SNARKs and folding schemes require hash functions to be both fast in native CPU computations and compact in algebraic descriptions (constraints). However, neither SHA-2/3 nor newer algebraic constructions, such as Poseidon, achieve both requirements. In this work we overcome this problem in several steps. First, for certain prime field domains we propose a new design strategy called Kintsugi, which explains how to construct nonlinear layers of high algebraic degree which allow fast native implementations and at the same time also an efficient circuit description for zeroknowledge applications. Then we suggest another layer, based on the Feistel Type-3 scheme, and prove wide trail bounds for its combination with an MDS matrix. We propose a new permutation design named Monolith to be used as a sponge or compression function. It is the first arithmetization-oriented function with a native performance comparable to SHA3-256. At the same time, it outperforms Poseidon in a circuit using the Merkle tree prover in the Plonky2 framework. Contrary to previously proposed designs, Monolith also allows for efficient constant-time native implementations which mitigates the risk of side-channel attacks.

Contact pressure in the proton exchange membrane fuel cell: Development of analytical models based on experimental investigation and a posteriori design of experiments

To understand the link between the physical properties of the Gas Diffusion Layer (GDL) and the overall performance of a Proton Exchange Membrane Fuel Cell (PEMFC), it is essential to investigate the impact of compressive loading on the physical parameters of the component, focusing on its electrical properties. This paper's experimental results obtained in the team's previous research are classified and analysed using a posteriori Design of Experiment (DoE). It allows us to determine the influential parameters on the component behaviour. Two analytical models are developed through regression analysis, allowing for predicting the output variables as a function of the input ones. The results are evaluated with statistical tools. The first model predicts the electrical Contact Resistance (CR) variation of the GDL as a function of mechanical compression and component type. The analytical results show that cycling compression has a negligible effect due to the lower number of applied cycles. The Micro Porous Layer (MPL) presence increases the CR, while the polytetrafluorethylene (PTFE) decreases it slightly. The GDL thickness is the most influential geometrical parameter. For this reason, a second analytical model is developed and predicts that CR is reduced primarily by increased mechanical compression and thicker GDLs.

An Improved Dempster–Shafer Evidence Theory with Symmetric Compression and Application in Ship Probability

Auxiliary information sources, a subset of target recognition data sources, play a significant role in target recognition. The reliability and importance of these sources can vary, thereby affecting the effectiveness of the data provided. Consequently, it is essential to integrate these auxiliary information sources prior to their utilization for identification. The Dempster-Shafer (DS) evidence theory, a well-established data-fusion method, offers distinct advantages in handling and combining uncertain information. In cases where conflicting evidence sources and minimal disparities in fundamental probability allocation are present, the implementation of DS evidence theory may demonstrate deficiencies. To address these concerns, this study refined DS evidence theory by introducing the notion of invalid evidence sources and determining the similarity weight of evidence sources through the Pearson correlation coefficient, reflecting the credibility of the evidence. The significance of evidence is characterized by entropy weights, taking into account the uncertainty of the evidence source. The proposed asymptotic adjustment compression function adjusts the basic probability allocation of evidence sources using comprehensive weights, leading to symmetric compression and control of the influence of evidence sources in data fusion. The simulation results and their application in ship target recognition demonstrate that the proposed method successfully incorporates basic probability allocation calculations for ship targets in various environments. In addition, the method effectively integrates data from multiple auxiliary information sources to produce accurate fusion results within an acceptable margin of error, thus validating its efficacy. The superiority of the proposed method is proved by comparing it with other methods that use the calculated weights to weight the basic probability allocation of the evidence sources.

Inspector Gadget

We introduce InspectorGadget, an Open-Source Python-based software for assessing and comparing the complexity of masking gadgets. By providing a limited set of characteristics of a hardware platform, our tool allows to estimate the cost of a masking gadget in terms of cycle count equivalent and memory footprint. InspectorGadget is highly flexible. It enables the user to define her own estimation functions, as well as to expand the set of gadgets and predefined microcontrollers. As a case-study, we produce a fair comparison of several masked versions of Kyber compression function from the literature, together with novel alternatives automatically generated by our tool. Our results confirm that an interesting middle ground exists between theoretical performance measures (asymptotic complexity or operations count) and real implementations benchmarks (clock cycle accurate evaluations). InspectorGadget offers both simplicity and genericity while capturing the main performance-related parameters of a hardware platform.

A Second Preimage Attack on the XOR Hash Combiner

The exclusive-or (XOR) hash combiner is a classical hash function combiner, which is well known as a good PRF and MAC combiner, and is used in practice in TLS versions 1.0 and 1.1. In this work, we analyze the second preimage resistance of the XOR combiner underlying two different narrow-pipe hash functions with weak ideal compression functions. To control simultaneously the behavior of the two different hash functions, we develop a new structure called multicollision-and-double-diamond. Multicollision-and-double-diamond structure is constructed using the idea of meet-in-the-middle technique, combined with Joux’s multicollision and Chen’s inverse-diamond structure. Then based on the multicollision-and-double-diamond structure, we present a second preimage attack on the XOR hash combiner with the time complexity of about O2n+12n/2+n−l2n−l+n−k2n−k+2l+1+2k+1) (n is the size of the XOR hash combiner and l and k are respectively the depths of the two inverse-diamond structures), less than the ideal time complexity O2n, and memory of about O2k+2l.

Permutation-Based Hashing Beyond the Birthday Bound

It is known that the sponge construction is tightly indifferentiable from a random oracle up to around 2c/2 queries, where c is the capacity. In particular, it cannot provide generic security better than half of the underlying permutation size. In this paper, we aim to achieve hash function security beating this barrier. We present a hashing mode based on two b-bit permutations named the double sponge. The double sponge can be seen as the sponge embedded within the double block length hashing paradigm, making two permutation calls in parallel interleaved with an efficient mixing function. Similarly to the sponge, the permutation size is split as b = r+c, and the underlying compression function absorbs r bits at a time. We prove that the double sponge is indifferentiable from a random oracle up to around 22c/3 queries. This means that the double sponge achieves security beyond the birthday bound in the capacity. In addition, if c > 3b/4, the double sponge beats the birthday bound in the primitive size, to our knowledge being the first hashing mode based on a permutation that accomplices this feature.

Improved Meet-in-the-Middle Nostradamus Attacks on AES-like Hashing

The Nostradamus attack was originally proposed as a security vulnerability for a hash function by Kelsey and Kohno at EUROCRYPT 2006. It requires the attacker to commit to a hash value y of an iterated hash function H. Subsequently, upon being provided with a message prefix P, the adversary’s task is to identify a suffix S such that H(P∥S) equals y. Kelsey and Kohno demonstrated a herding attack requiring O(√n · 22n/3) evaluations of the compression function of H, where n represents the output and state size of the hash, placing this attack between preimage attacks and collision searches in terms of complexity. At ASIACRYPT 2022, Benedikt et al. transform Kelsey and Kohno’s attack into a quantum variant, decreasing the time complexity from O(√n · 22n/3) to O( 3√n · 23n/7). At ToSC 2023, Zhang et al. proposed the first dedicated Nostradamus attack on AES-like hashing in both classical and quantum settings. In this paper, we have made revisions to the multi-target technique incorporated into the meet-in-the-middle automatic search framework. This modification leads to a decrease in time complexity during the online linking phase, effectively reducing the overall attack time complexity in both classical and quantum scenarios. Specifically, we can achieve more rounds in the classical setting and reduce the time complexity for the same round in the quantum setting.

Functions of Stereotypes in Mass Culture in the Context of Critical Multiculturalism

This article offers a project-based English lesson with university students, which is aimed at studying the way that stereotypes function in mass culture. Critical multiculturalism is currently gaining more and more attention among researchers. Its rise is reflected in English language study books, which stands in stark contrast with the inexhaustible popularity of stereotypes in popular culture. Meanwhile, it is noteworthy that stereotypes are viewed not only as clichéd images of ethnic and socio-cultural groups, but they also participate in categorizing the flow of incoming information and thus act as an essential tool of cognition. During the preparation for the project-based lesson, students studied and analysed the functioning of stereotypes in various samples of popular culture, including commercials and memes, and then presented the results of their research in class. With the help of the teacher, the students identified the following functions of stereotypes in popular culture: cognitive, persuasive, integrative, reflexive, entertaining (including sarcastic), therapeutic, and the function of compression. Further research may continue this list and describe the hierarchical relations between the functions.

Types and functions of the neologisms in E. Zamyatin’s novel "We" (to the 140th anniversary of the birth)

The article examines the neologisms used in the text of E. Zamyatin ’s novel "We". The aim is to identify their types and determine their functions in the work. The research establishes the total number of word-formation innovations and concludes that potential words, primarily compound adjectives and adverbs, predominate in the inventory of neologisms in the text of the novel "We". Research methods: using word-formation analysis, the types of new formations are established. The functions of neoderivatives in the text are determined and systematised based on structural-semantic and linguostylistic analysis. The study identifies the primary methods of creating neologisms (compounding, compounding-suffixation, blending, suffixation) and highlights several genuine occasionalisms created by Zamyatin. The research demonstrates that the neologisms in the novel are multifunctional. They serve to create figurative characterisations of the personae, as well as the depicted phenomena and objects. Moreover, these neologisms perform the characterological and compression functions in conjunction with the nominative function proper (denote the realities of the Unified State). They contribute to the development of the recurring motifs in the work and largely determine its leitmotif structure. The paper emphasises that the nature of the neologisms in the novel "We" reflects the characteristics of E. Zamyatin ’s individual style as a whole and is associated with the aesthetic principles of neorealism the writer substantiated (creation of integral images, conveyance of visual impressions, and others).

On the origin of Sanchez-Lacombe equation of state theory in hydrostatic strain energy model for rubber-like materials

To capture the volume deformation of rubber-like materials, the strain energy density (SED) function of a compressible hyperelastic model is formulated as the hydrostatic/liquid-like term from interchain interaction changes plus the compressible elastic term owing to elastic deformation of crosslinking network. Notably, the former term dominates volume responses. Although the physics of the hydrostatic term is relatively clear, to our knowledge, few physically-based models are available. However, in our previous work (Liu and Lu, 2023), we constructed a physically-based hydrostatic SED function inspired by the Flory-Orwoll-Vrij equation of state (EOS) theory for pure polymer fluids, and proposed the general strategy for developing hydrostatic functions according to the EOS theories. Sanchez-Lacombe EOS theory (note: a type of lattice-fluid EOS theory) inspired this work. We assume: (i) a rubber-like material consists of polymer segments occupying lattice sites and unoccupied/vacant lattice sites, and the compressibility of the material corresponds to changes in vacant sites fraction; (ii) the hydrostatic strain energy is associated with the interchain interaction energy change and the mixing entropy change between network and vacant sites. According to the Helmholtz free energy in Sanchez-Lacombe EOS theory and limiting our attention to the isothermal condition, another physically-based hydrostatic SED function is constructed; a specific compressible hyperelastic model is provided by further combining compressible 8-chain elastic SED function. The basic framework of this compressible model is inherently consistent with the Flory-Rehner framework for swollen elastomers. Our model provides good predictions for volume deformation data of ten different rubber-like materials in hydrostatic compression (HC), uniaxial tension (UT), and constrained uniaxial compression (CUC). The proposed model reveals that HC, CUC, or uniaxial compression correspond to the entropy-decreasing process and they all are controlled by entropy changes; while for UT, equibiaxial tension, or pure shear, the entropy first increases and then decreases, and the interchain interaction energy and entropy changes control the responses for initial small stretches and remaining large stretches, respectively. This study aims to provide a new physical insight and a valid physically-based hydrostatic SED function for the compressibility of rubber-like materials.

Ключевой криптоалгоритм по схеме «сэндвич» на основе хеш-функции «Стрибог»

We propose a keyed cryptographic algorithm based on the “Streebog” hash function. We do not make any structural changes to the hash function itself, but only introduce a special type of padding. As a result, the key appears on both sides of the message in so-called “sandwich” manner - hence the name Streebog-S for our construction. “Sandwich” properties make it possible to simplify defenses against side-channel attacks while maintaining their effectiveness. We prove that Streebog-S and other algorithms based on “Streebog”, HMAC-Streebog and Streebog-K, remain secure as pseudorandom functions (PRF) and message authentication codes (MAC) even when almost all internal states are leaked to the adversary. This leakage resistance requires additional properties from the underlying compression function, namely collision- and preimage-resistance.

Optimization of thermal conductivity and lightweight properties of clay bricks

As the demand for energy increases worldwide, the construction industry, one of the most energy-intensive sectors, requires lightweight and high-thermal-performance materials. To address this, a multi-objective optimization approach was used in this study to identify the most suitable solutions for producing strength-fired clay bricks with low thermal conductivity. Porous bricks were produced with organic waste additives to illustrate the relationship between compressive strength and thermal conductivity. A 3-factor and 3-stage Box-Behnken experimental design was utilized, with a pore-forming additive ratio (0–10% by weight of pine nut shells), firing temperature (850–1050 °C), and firing time (2–6 h) as the variables. The fired bricks' physical, mechanical, and thermal properties were determined using standard analysis methods. The bricks' compressive strength and thermal conductivity functions were generated using neuro-regression systematics. Multiple targets were defined, including minimizing the thermal conductivity and maximizing the compressive strength of the bricks. The genetic algorithm was employed to identify Pareto-optimal solutions, and the final sets of low thermal conductive-strength brick production were chosen based on these solutions. Two sets were proposed to achieve the lowest thermal conductivity, and the results confirmed the validity and feasibility of the optimization study.

Possibilities of Determining K-Value and Activity Index for Ground Granulated Blast Furnace Slag

This paper deals with the determination of k-value and activity index for ground granulated blast furnace slag (GGBFS). The aim of this paper is to determine the activity index and k value for different CEM I cement substitutes with ground granulated blast furnace slag. determination of the k-value is based on the relationship of the water/cement ratio and the compressive strength of concrete with GGBFS. The next goal is to create a mathematical function that describes the development of compressive strength depending on the age of the cement mortar or concrete and the amount of cement replacement with GGBFS. Based on the achieved compressive strengths were designed compressive strength function for concrete and cement mortar with high coefficient of determination (above 0.9). Furthermore, k-values were determined for different ages of concrete and replacement of cement with finely ground slag. These k-values increase as the age of the concrete increases.

Accurately and explicitly simulating distinct tensile and compressive behaviors of various concretes with new elastoplasticity model

PurposeThis paper aims to present a direct analysis to demonstrate why markedly different tensile and compressive behaviors of concretes could not be simulated with the Drucker–Prager yield criterion.Design/methodology/approachThis study proposed an extended form of the latter for establishing a new elastoplasticity model with evolving yield strengths.FindingsExplicit closed-form solutions to non-symmetric tensile and compressive responses of uniaxial specimens at finite strain are for the first time obtained from hardening to softening.Originality/valueWith such exact solutions, the yield strengths in tension and compression can be explicitly prescribed by uniaxial tensile and compressive stress-strain functions. Then, the latter two are further provided in explicit forms toward accurately simulating tensile and compressive behaviors. Numerical examples are supplied for meso-scale heterogeneous concrete (MSHC) and high-performance concrete (HPC), etc. Model predictions are in good agreement with test data.

Weak fault detection based on amplification-compression function and sparse spike deconvolution

Weak fault detection is still a hotspot in these years. The key of this work is to enhance the ratio of signal to noise (SNR). Then a new extraction method of weak fault impact based on amplification algorithm is proposed. Since the fault impact is related to bigger derivative, the amplification function combined with the derivative of the vibration signal is used to amplify the amplitude of the impact. Then Sparse Spike Deconvolution (SSD) which has been widely used in earthquake for impact detection is able to extract small impact from the signal processed by amplification function. Then, in order to enhance the periodicity of fault impacts, the compression function is used to compress the amplitude of bigger impacts according to different scales. At last, the experiment result shows that the proposed method is more effective than the common envelope analysis.

Weighted Decision Enabled Phase Retrieval Receiver With Adaptive Intensity Transformation

Phase-retrieval (PR) receivers can reconstruct complex-valued signals from two de-correlated intensity measurements by the use of iterative PR algorithm, without the assistance of any optical carriers. However, both the computational complexity with hundreds of iterations and the limited PR accuracy prevent it from being applied to high-speed photonic interconnections. In current submission, we propose a weighted decision enhanced PR receiver with adaptive intensity transformation (WD_AIT_PR). The weighted decision based on a compressed sigmoid nonlinear function is helpful to avoid the hard-decision (HD) errors, leading to the performance enhancement of the PR receiver, in terms of both convergence speed and PR accuracy. When the 56 GBaud 16QAM signal after transmission over 80 km standard single mode fiber (SSMF) is reconstructed, the WD_AIT_PR receiver is numerically verified to possess the faster convergency speed with only 70 iterations and the best steady BER performance by reducing the required optical signal-to-noise ratio (OSNR) by 0.8 dB, 1.8 dB and 1.8 dB in order to reach 7% HD forward error correction (HD-FEC), in comparison with the HD_AIT_PR receiver by replacing WD with HD, the PR receiver with the phase reset (PR_PR) and the PR receiver with adaptive intensity transformation (AIT_PR), respectively. Meanwhile, the WD_AIT_PR receiver is robust to transmission impairments, including transmitter-side I/Q imbalance, receiver-side skew, the noise imbalance between two intensity measurements, laser phase noise, and laser wavelength drift. Finally, the enhanced performance of the WD_AIT_PR receiver is experimentally verified through recovering 25 GBaud 16QAM signals under the condition of 40 km SSMF transmission.

Dynamic calibration of a new secondary settler model using Cand. Microthrix as a predictor of settling velocity

Climate change is projected to increase the frequency of hydraulic shocks on urban water systems, affecting water resource recovery facilities (WRRFs). In these facilities, the settleability of activated sludge is a critical hydraulic bottleneck. However, to date, the dynamic prediction of hindered settling velocity (v0/rH) has remained unresolved. To address this significant knowledge gap, this study presents an assessment of microbial community predictors of hindered settling velocity. Through a regression analysis of independent laboratory and full-scale experimental data, we identified a close association between the relative abundance of Candidatus Microthrix filamentous bacteria and hindered settling velocity parameter values. While no direct association was observed between filamentous abundance and compression settling parameters, we propose linking the dynamic calibration of the compressive solid stress function to v0/rH. Notably, our results demonstrate, for the first time, the efficacy of dynamic calibration of SST models using the relative abundance of filamentous microbial predictors in a simulation model of the Kloten-Opfikon full-scale WRRF. Furthermore, besides Cand. Microthrix, Thiothrix is found to be a putative predictor for biomolecular SST calibration. These findings shed light on the potential of microbial communities to predict hindered settling velocity in WRRFs and offer valuable insights for improving wastewater treatment processes in the face of climate change challenges.

ADAPTIVE DOUBLE NEO-FUZZY NEURON AND ITS COMBINED LEARNING

The subject of the study in the article is the process of data classification under conditions of fuzziness and a limited volume of training sample. The goal is to enhance the double neo-fuzzy neuron within the framework of solving the data classification task with constraints on the training sample volume, processing time, as well as fuzziness and nonstationarity of input data. The tasks include improving the double neo-fuzzy neuron to enhance the system's approximation properties and developing a combined system learning method to ensure fast performance in an online mode. The approaches used are lazy learning, supervised learning, and self-learning. The following results have been obtained: the double neo-fuzzy neuron has been modified by introducing a compressive activation function at the output, creating conditions for building a neo-fuzzy network capable of adapting to non-stationary input data in an online mode and avoiding the vanishing gradient problem. Conclusion. A combined learning method for the double neo-fuzzy neuron has been proposed, involving parallel utilization of lazy learning, supervised learning, and self-learning with the "Winner Takes All" rule, followed by automatic formation of membership functions, enabling fast online classification in the presence of outliers in the input data.