In this article, we will consider the Vigenere table for the Russian alphabet, namely its significance in development. Let's get acquainted with the terminology, historical facts. We will study decryption and its methods, as well as much more, which ultimately will allow us to clearly define the concept of the Vigenere table.
Introduction
There is the concept of āinformation encryptionā - it represents a certain mechanism for interpreting information in a different form, which can only be known if you know how to decrypt it.
The VigenĆØre cipher is one of such methods of the polyalphabetic method of encrypting information by making changes to the alphabetic text, which can only be read if you know the keys. This multi-alphabet substitution was not invented at once. The first scientist to describe this method was J. Battista Bellazo. He did this on the pages of La cifra del. Sig. in 1553, however, the method was named after B. Vizhener, a diplomat from France. Its methodology is quite simple to understand and implement. It is also inaccessible to conventional cryptanalysis tools.
Historical data
L. Alberti, a well-known specialist in the fields of architecture and philosophy, in 1466 submitted for examination and evaluation a treatise that contained information about encryption, he was sent to the office of the Pope. The information told about various ways of performing this action. The final result of the work was presented to him in a personally developed data encoding method, which he called āa cipher worthy of kingsā. This encryption mechanism was a multi-alphabetic structure that formed an encryption disk. The invention of the printing device in Germany in 1518 provided a new space for the development of cryptography.
In 1553, another step was taken allowing this area of āāhuman activity to develop. This was done by J. Bellazo. He called his work "Signora Bellazo's Code." Here, a key or phrase was used as a key, which served as a password. In the future, these ideas were transformed by compatriot Bellazo, namely, J. B. Port. The main change was the proposal to abandon the standard following of the alphabetical order in the first table row and, therefore, the transition to the order taken from arbitrary topics that can be used as a key needed for decryption. In accordance with the lessons of cryptography, the rows of the tables retained the previous cyclic nature of the shifts. The book āOn Secret Correspondenceā published by the Porta included information on the bigram cipher.
Mid 16th century, Italy. Here appeared a book edition of the work of J. Cardano, aimed at reflecting innovations in cryptographic ideas. For example, the concept of "Cardano lattice" appeared.
After Blaise got acquainted with the work of Bellazo, Cardano and other thinkers, he also became interested in cryptographic business. In the future, he created the Vigenere cipher. Another significant work of his was the writing of a treatise on ciphers. In it, the author tried to explain the basics of cybernetic cryptography.
Cipher Reviews
Vigener's table and data encoding methods that resulted from its use were extremely resistant to āmanualā type hacking. A specialist in mathematics and writer L. Carroll conferred the title āunbreakableā on this cipher system, which he expressed in an article on the āAlphabetical Codeā published in 1868.
After 59 years, one of the American magazines spoke about the method of polyalphabetical encryption of alphabetic text, invented by Vizhener, as well as Carroll earlier. However, in the 19th century, the Kasiski method was invented, which made it possible to refute these claims by breaking the cipher system.
Gilbert Wernham made an attempt to improve the hacked cipher, but even taking into account its improvement, he remained unstable to cryptanalysis. In the future, Vernam himself created a truly system that cannot be decoded.
General information
The Vigenere table for the English alphabet had many different forms of interpretation in the modes of operation. For example, Caesarās cipher suggested an alphabetical shift by a certain number of positions. For example, a shift of three letters would mean that the letter A would become D, and B would turn into E. The cipher created by Vizhener is formed from a series of several Caesar encryption systems in series. Here, any shift can have different meanings. The encoding process may involve the use of special alphabetic plates or squares (tables) of Vigenere. Twenty-six characters were created for the Latin alphabet, and any subsequent line in them was shifted by a certain number of positions. The symbol of the key word determines the choice of alphabet to use.
Decryption
Using encryption using the Vigenere method , a āblurringā of the general characteristic of the frequency of repetition of characters in the source occurs. However, there remain features whose appearance in the text is regularly reproduced. The main weakness of this encoding is the repetition of keys. This allows you to build a cryptanalysis process, consisting of two stages:
- Determining the password length. This is done by analyzing the distribution frequency of various text thinning. In other words, they take a source with a cipher in which every second letter is a part of the code, then use the third, etc. If you can reach the point where the frequency distribution has too much difference in uniformity, then you can determine the length of the word used in as a key.
- Using cryptanalysis tools, which is the total number of Caesarās ciphers that can be easily cracked by looking at them separately from each other.
It is determined by Kasiski and Friedman tests.
Cashier Way
The first who was able to develop an algorithm for breaking the cryptographic method of Vigenere was C. Bebbage. As an incentive, he used the information obtained through an exchange of letters with J. Twits, where he claimed that he was able to develop a new encoding system. Charles Bebbage proved the opposite to his interlocutor by reducing him to a special case of Vigenere's works. After that, Twis advised Charles to crack the source. The decryption of the text hid the words of the poem of A. Tennyson, and the name of his wife, Emily, served as the key word. The publication of the opening did not take place at the request of the cracker. The same algorithm was discovered by the officer of the Prussian army, Frederick Wilhelm Kasiska, in whose honor he was named.
The idea is based on the periodic key flow technique. The natural form of the language also contains letter combinations, which can often be repeated and are called bigrams and trigrams. Their repetition frequency allows a chance to appear that will help determine the decryption key. The distance between the repetition of certain structures should correspond to the multiplicity of the length of the slogan. By calculating the longest total duration of each such distance, we can obtain the working hypothesis of the key length.
Kappa test
Another way to decrypt the Vigenere table and the encoding resulting from it can be considered a test created by V. Friedman. This method was developed in 1920. Here we used the concept of a coincidence index, which could measure the repetition rate of specific characters, which would allow to crack the cipher system. Having information that randomly selected characters can coincide with a chance of approximately equal to 0.067% (for English), you can also determine the probability of their coincidence in the text. Thanks to this, you can create an estimate of the key length.
Frequency analysis
After you can determine the size of the key length, you can begin to enter text in various columns in which they will correspond to any key character. All columns are formed thanks to the source code encoded using Caesar's cipher. And the key to this coding method is one voice unit for the Visionary system. Using tools that allow you to crack Caesarās ciphers, thereby complete decryption of the text.
An improved form of the Kasiski test, known as the Kirchhoff method, is based on comparing the appearance of frequencies with specific characters in each column. Thanks to them, the repetition rate of the symbol in the source texts is compared. How to use the VigenĆØre table, knowing all the symbols of the keys, it becomes clear to the cryptanalyst and it will not be difficult to read it in the final decryption process. The means of the Kirchhoff method are not applicable in cases where this lattice of letters is scrambled. That is, there is a departure from the standard sequence of letters in the alphabet. However, it is important to know that the match test is still comparable to the Kasiski method, and therefore they can be used to determine the key length for special cases.
Variability
The alphabetical system can be based on many other squares, of which there are quite a lot, and they are easy to remember. Applicable on a par with Vizhener's square. Famous analogies include a square named after Admiral F. Beauford. It represents the rows of the Vigenere table, but directed in the opposite direction. Sir Francis Beaufort was the man who created the scale for determining wind speeds.
To summarize
An example of the Vigenere table can be seen in the figure below.
Having general information about this encryption method, its history, development and relationship with various scientists, decryption methods, advantages and disadvantages, we can now clearly define this concept as a special way to transform information from one form to another in order to hide the source data from a certain a number of persons. The ability to code messages was an important strategic component of all the wars of mankind.