A blockchain, or in other words a chain of transaction blocks, is distributed database that maintains an ordered blocks reliably connect the information contained them. Copies are usually stored on multiple computers and synchronized accordance with rules building which provides secure change-resistant storage information. To build linked lists hashing used. Hashing special cryptographic primitive one-way, resistance to collisions search for prototypes computation hash value (hash message...

Abstract The known method of high nonlinear S-boxes generation based on the gradient descent [Kazymyrov, O. V.: Methods and Techniques Generation Nonlinear Substitutions for Symmetric Encryption Algorithms. thesis scholarly degree candidate technical sciences, speciality 05.13.21 - Information security systems, Kharkiv National University Radioelectronics, Kharkiv, 2014. (In Russian)] requires consecutive applications several criteria each formed substitution. This paper presents an...

This paper presents improvement of the high nonlinear S-boxes generation method by appropriate selection criteria application order which decreases required computation power for S-box generation. The proposed modification allows a byte with nonlinearity 104, algebraic immunity 3 and maximum difference distribution table 8 within approximately 30 minutes single PC running time.

Two double-spend attack strategies on a proof-of-stake consensus are considered. For each strategy, the probability of its success is obtained, which depends network parameters and number confirmation blocks. These results can be used to define how many blocks vendor should wait after correspondent transaction before sending goods or services.

We propose new mathematical models of splitting attacks targeted at two major consensus protocols applied in cryptocurrencies. Obtained upper bounds probability successful fork maintenance by an attacker allows to get estimates on block expectation number for securing the system against attacks.

We propose a new approach for secure decentralized and censorless upgrade of existing cryptocurrencies to newly created tokens without interaction from any external information sources (oracles). The proposed scheme is based on burning implemented via the multi-currency auction. auction carried out blockchain token using smart-contract that processes participants' bids burnt other supports price discovery algorithm each cryptocurrency with no oracles or trusted source information. Contrary...

There are many ARX-based symmetric primitives that form the core of modern lightweight cryptography. The paper considers known methods proving differential properties ciphers based on application partial difference distribution tables, probabilistic neutral bits and SAT solvers. long trail strategy allows designing provable secure block is also considered. open problems ARX-ciphers security to attacks formulated. It underlined there no universal theory evaluating any primitive cryptanalysis.

Electronic trust services are becoming an integral part of the information space.With reliable implementation basic as electronic signature and authentication, it is possible to build more complex systems that rely on them, particularly voting system.In paper, new concept for developing a decentralized system using blockchain technology proposed.The two-level architecture provides secure process without redundancy existing (not based blockchain) systems.The presented blockchain-based...

Context. We consider security properties of decentralized blockchain-based consensus protocols. The object research is blockconfirmation time for users to get assurance that their transaction will not be reverted.Objective. goal the paper analyze double-spend attacks on different systems and compareresulting probabilities attacker’s success.Method. presented two models types Ouroboros protocol (for general covert adversaries).The allow calculating exact number slots needed achieve required...

This paper presents three approaches to search for one-round differential characteristics with high probability post quantum lightweight block cipher Cypress-256. The presented methods include the selection of appropriate input differences round function based on properties modulo addition operation. proposed optimized method allowed find Cypress-256 1/4.

We study probability change of double spend attack on Proof-of-Work consensus protocol depending network parameters in the model with continuous time. analyze effect block generation intensity vulnerability to attack, and provide analytical expressions for security threshold upper bound intensity.

A specific number of transaction confirmation blocks determines average time receiving and accepting payments at cryptocurrencies, the shortest for same level blockchain security provides best user properties. Existing papers on Bitcoin use implicit assumption prompt spreading over network (that is not always case real world conditions). The newer publications with rigorous analysis proofs properties that take into account delays provide asymptotic estimates, no numbers blocks.

In this work it is considered the differential cryptanalysis of lightweight block cipher Cypress that was recently developed in Ukraine. Firstly, a model for introduced. Then method searching multi-round characteristics Cypress-256 proposed. The includes construction big set one-round with further combination them. application proposed reveled no match within constructed good from point view its strength to cryptanalysis. analysis showed inputs minimal Hemming weight are not always leads...

The paper presents the formulas for probability of a double spend attack on blockchain with Proof-of-Work consensus protocol network non-zero synchronization time.The results show that depends essentially block delivery time and intensity generation.More precisely, such increases when product these two values increases.The analytical obtained in this allow not only to calculate exact value probability, but also define minimal number confirmation blocks sufficient guarantee security against...

We obtained analytical expressions of upper estimates for success probability a double spend attack on DAG-based consensus protocol SPECTRE, depending network parameters. Using such estimates, it is possible to evaluate the number confirmation blocks that sufficient prevention attacks.

The paper is devoted to the comparison of performance prospective lightweight block cipher Cypress with performances known modern ciphers such as AES, SPECK, SPARX etc. measurement was done on different platforms: Windows, Linux and Android. On all platforms selected, showed best results. Cypress-256 highest Windows x32 (almost 3.5 Gbps), 64-bit (over 8 Gbps) Android (1.3 Gbps). x64 result obtained by Cypress- 512 5

In this paper we present a reputation-based incentive model for community-driven decentralized analysis of cryptocurrency platform development proposals. Firstly, consider how the rewards Proposal Assessors (who write assessments on proposals) and Veteran rank assessments) depend different types work they've done. Then, definition properties reputation function rationale selecting coefficients work.

Context. The object of study this work is the arrival processes block symmetric ciphers to state a random permutation.Objective. Clarification by means computational experiments values dynamic parameters some modern thestate permutation, which can be important when evaluating their effectiveness.Method. Methods consists in determining differential activation (programming models) sets theinput difference and subsequent determination minimum number S-boxes-activated first cycle encryption,...