Most messages on the network are transmitted in encrypted form, since open communication channels are not protected from
The problem of finding cipher vulnerabilities is alwaysspicy. To avoid breaking them, it is necessary to strengthen the protection of ciphers from possible leaks and test encryption systems to find weak points. All ciphers are divided into two large classes - block and stream. Streaming data has a great advantage: it provides an acceptable speed of information transfer, including for sending images and videos. Stream encryption is based on combining data with a random sequence using a special algorithm. For such encryption, special keys are used. There are many requirements for keys so that data encrypted with them can be generated and stored. However, it is not always possible to ensure that a reliable key is used. Therefore, stream encryption systems require preliminary testing for vulnerability.
“I was interested not only in offeringan algorithm that can determine the source text of a transmitted message, but also find the possibility of restoring the text both in theory and in practice directly—without defining the key,” comments the author of the work, graduate student at MIEM NRU HSE Anastasia Malashina. For the task of searching for vulnerabilities, she investigated a method that allows us to evaluate the possibility of keyless recovery of individual message segments in cases of using a vulnerable cipher or leaks in a communication channel.
Using information about possible optionseach of the encrypted characters of the original message, the algorithm iterates over the values for all other characters. If there was a vulnerability in the original cipher, this method allows you to detect it. The proposed algorithm was implemented in a special program, part of which was recently patented. This program allows you to evaluate the reliability of encryption systems and the possibility of breaking them in the event of a data leak.
“During the work, I examined the buildingjournalistic texts and an open corpus of the Russian language. Statistical analysis of dictionaries made it possible to estimate the entropy of texts, for which the possibility of partial decryption was subsequently assessed. In addition, dictionaries compiled on the basis of corpora are used in the experimental part of the study to implement a dictionary attack. Similar results were obtained for the English language based on the iWeb corpus,” adds Malashina.
The results of the study are presented in the article “Development of tools for studying the information characteristics of natural language.”
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