USAGE OF THE STEGANOGRAPHIC ALGORITHMS FOR TEXT INFORMATION HIDING
Authors: Lagun A. 
Published: October 2019

Today cryptographic and steganographic systems provide the best information security of society. Cryptography transforms information into the incomprehensible form with using the cryptographic keys and algorithms. Steganography hides the secret information in unknown place of object.

The steganographic algorithms, which hide message in text container, are researched in the article.

For process of hiding are used the text file-container properties. The hide message converts to the binary numbers system. User puts ones or zeros into the defined places of text file-container. These places have special characteristics.

There may be two types of hiding: insertion and replacement.

In case of insertion the hiding message adds to file-container with using invisible characters in viewing mode of text file. Then the size of full container with hided message is bigger than size of empty container.

If used the replacing method then the characters of file-container replace to other characters that are almost the same as the first ones. For example, anyone is possible replacement of characters that have the same appearance in different languages. In this case the sizes of the empty and filled container remain the same.

One of the simplest hiding methods is insertion the variable quantity of the space characters between words of text file. Suppose, that zero of hidden message is coded by one space character and one - is coded by two space characters. Therefore, depending on hidden message one or two space characters are located in different places of the text.

Also, the author considers another hiding type, which uses the same view of some characters of different languages. If you look at the characters in Ukrainian and English, than the 18 characters in the each language is the same – 'a','c','e','i','o','p','x','A','B','C','E','H','I','K','O','P','T','X'. When hiding for the values of zeros in hidden message the file-container remains the same, and for the values of ones in hidden message the characters of language file-container replace to the same characters of another language (Ukrainian-English).The results of the algorithm work show us, that when using characters from different languages in the hiding process, the full file-container is much smaller than when encoding the space characters.

The last algorithm which is considered in work uses tail space characters. It forms a filled container with enlarged text strings depending on the number of space characters which the hidden message determines. One character of hidden message is written in two file-container text strings. In particular the binary representation of each character is divided into two parts with four bits, and at the end of each text string is written no more than 15 space characters. The number of space characters corresponds to the decimal value of each part. To ensure hiding of secret message full container has the form aligned to the left edge of the text.

Considered algorithms of hiding message in text container are used for the confidential information defense. Algorithms, which use insertion of invisible characters, allow hiding the amount of information that corresponds to the number of space characters with certain characteristics. The most of replacement algorithms hide more information than insertion algorithms. Also replacement algorithms do not change file-container size. For example, algorithm, which replace characters of different alphabets, hides such amount of information, which depends on the statistics of used languages.

The most problem of using text containers is providing its steganographic defense. In particular, if user enables the unprintable character view in a text editor, then could see the some statistic of location invisible symbols added by the insertion methods. Therefore decoding of hidden message is simplified. The hidden message with using replacement algorithms is more defensible, but using of compression algorithms to the full container deletes the hidden information.