On retrieval of secret key parameters from symmetric block cipher O’zDST 1105:2009 using modified SQUARE cryptanalysis

In this article, the application of SQUARE cryptanalysis to the Uzbek standard of symmetric block encryption is investigated. We have constructed an efficient attack on the 1st and 2nd rounds of the Uzbek algorithm, allowing to retrieve several bytes of the secret key. We found that the constructed attack is almost surely successful. This article highlights the importance of studying the interaction of different transformations, as the success of the devised attack relies on using operations in the ring modulo 256, rather than in a finite field.