This paper considers a new method for obtaining an S-box, which is one of the nonlinear transformations used in modern block-symmetric cipher systems. This method is based on modular arithmetic, that is, exponentiation modulo polynomial in extended Galois fields $GF\left(2^8\right)$. The indicators and criteria of efficiency of the obtained S-box (balance, Hamming distance, distribution criteria, autocorrelation, algebraic immunity, cyclic structure of the S-box) are analyzed. The cryptographic characteristics are presented in comparison with the substitution boxes of known modern block ciphers. In addition, the resulting S-box was investigated by the methods of linear and differential cryptanalysis. In the future, the proposed S-box will be used in the developed encryption algorithm designed for the pre-encryption of confidential information.

This paper proposes the new hash algorithm HBC-256 (Hash based on Block Cipher) based on the symmetric block cipher of the CF (Compression Function). The algorithm is based on the wipe-pipe construct, a modified version of the Merkle-Damgard construct. To transform the block cipher CF into a one-way compression function, the Davis-Meyer scheme is used, which, according to the results of research, is recognized as a strong and secure scheme for constructing hash functions based on block ciphers. The symmetric CF block cipher algorithm used consists of three transformations (Stage-1, Stage-2, and Stage-3), which include modulo two addition, circular shift, and substitution box (four-bit S-boxes). The four substitution boxes are selected from the “golden” set of S-boxes, which have ideal cryptographic properties. The HBC-256 scheme is designed to strike an effective balance between computational speed and protection against a preimage attack. The CF algorithm uses an AES-like primitive as an internal transformation. The hash image was tested for randomness using the NIST (National Institute of Standards and Technology) statistical test suite, the results were examined for the presence of an avalanche effect in the CF encryption algorithm and the HBC-256 hash algorithm itself. The resistance of HBC-256 to near collisions has been practically tested. Since the classical block cipher key expansion algorithms slow down the hash function, the proposed algorithm is adapted for hardware and software implementation by applying parallel computing. A hashing algorithm was developed that has a sufficiently large freedom to select the sizes of the input blocks and the output hash digest. This will make it possible to create an almost universal hashing algorithm and use it in any cryptographic protocols and electronic digital signature algorithms

The distinguishing feature of hash-based algorithms is their high confidence in security. When designing electronic signature schemes, proofs of security reduction to certain properties of cryptographic hash functions are used. This means that if the scheme is compromised, then one of these properties will be violated. It is important to note that the properties of cryptographic hash functions have been studied for many years, but if a specific hash function used in a protocol turns out to be insecure, it can simply be replaced with another one while keeping the overall construction unchanged. This article describes a new post-quantum signature algorithm, Syrga-1, based on a hash function. This algorithm is designed to sign r messages with a single secret key. One of the key primitives of the signature algorithm is a cryptographic hash function. The proposed algorithm uses the HAS01 hashing algorithm developed by researchers from the Information Security Laboratory of the Institute of Information and Computational Technologies. The security and efficiency of the specified hash algorithm have been demonstrated in other articles by its authors. Hash-based signature schemes are attractive as post-quantum signature schemes because their security can be quantified, and their security has been proven.

This paper proposes a new post-quantum signature scheme, Syrga2, based on hash functions. As known, existing post-quantum algorithms are classified based on their structures. The proposed Syrga2 scheme belongs to the class of multi-use signatures with state retention. A distinctive feature of state-retaining signatures is achieving a compromise between performance and signature size. This scheme enables the creation of a secure signature for r messages using a single pair of secret and public keys. The strength of signature algorithms based on hash functions depends on the properties of the hash function used in their structure. Additionally, for such algorithms, it is possible to specify the security level precisely. In the proposed scheme, the HBC-256 algorithm developed at the Institute of Information and Computational Technologies (IICT) is used as the hash function. The security of the HBC-256 algorithm has been thoroughly studied in other works by the authors. In contrast to the Syrga1 scheme presented in previous works by the authors, the Syrga2 scheme provides for the definition of different security levels determined by the parameter τ. This paper experimentally demonstrates the impossibility of breaking the proposed scheme using a chosen-plaintext attack. Additionally, the scheme’s performance is evaluated for signature creation, signing, and message verification.

A new symmetric block cipher algorithm called AL02 has been developed. The algorithm scheme provides five-round encryption of 128-bit blocks, while the data size at the input and output of the S-box is 8 bits. The main transformation is the F transformation. The difference between the proposed algorithm and the classical scheme is that the F transformation provides the maximum possible dependence of the output vector bits on the input bits and is based on “modulo 2 addition” and a substitution S-box. To assess the strength of the AL02 algorithm, it was programmatically implemented in the C programming language. During the analysis, the cryptographic properties of the developed encryption algorithm were tested. The algorithm was tested for statistical security. For an experimental assessment, in order to ensure that the ciphertext is not inferior to a random sequence in its properties, the well-known sets of statistical tests by NIST (National Institute of Standards and Technology) and Donald Knuth were used. The property of the avalanche effect was also checked. The strength was evaluated using the methods of differential and linear cryptanalysis.

This paper offers a lattice-based digital signature construction, optimized for the provision of post-quantum security in resource-constrained environments, such as Internet of Things (IoT) devices. The offered scheme is built upon structured hardness assumptions, defined over polynomial rings that exhibit inherent algebraic symmetry. By exploiting the cyclic properties of these ring structures and implementing efficient Number Theoretic Transforms (NTTs), the construction achieves compact signatures that are under 3 KB and a runtime feasibility that uses less than 10 KB of RAM. The signature generation process incorporates balanced rejection sampling and carefully designed polynomial encodings that preserve structural regularity and computational efficiency. The security of the offered scheme is proven. The benchmark results generated from using the ARM Cortex-M4 platform demonstrate its practical usability. This study highlights how symmetric algebraic frameworks based on lattice-based cryptography can be leveraged to achieve both theoretical security and real-world performance in the post-quantum era.