The Built on Feistel Network Architecture Block Ciphers Modification

The article considers the method of implementing Shannon’s idea of building a cryptographically stable system by repeatedly applying relatively simple cryptographic transformations. At the same time was being solved the problem of simultaneously reducing the level of statistical vulnerabilities of the original sequence typical for block ciphers and fundamentally justified by the Kerckhoffs principle. It is suggested to reduce the sensitivity of existing cryptographic algorithms to existing cryptanalysis tools by implementing a universal solution suitable for any encryption algorithm. The main property of this solution is to increase crypto resistance by increasing the length of the key and the encrypted information block. The developed algorithms use the modification technique of symmetric block ciphers built on the architecture of the Feistel network. The proposed method is characterized by simplicity and transparency of solutions. An analysis of its main characteristics concerning classical algorithms built on the architecture of the Feistel network was carried out. It has been established that the time of multi-stage encryption decreases to the time of implementing a single round of encryption. Accordingly, the decryption time reduces to the execution time of two rounds - the encryption round and the decryption round. Therefore, high indicators of the cipher’s two main properties - bandwidth and reliability - are provided.