POLYBIUS SQUARE DECODER PLUS
POLYBIUS SQUARE DECODER SERIES

This betraysВ that the cipher is based on a 6 x 6 grid.Д«y adding aВ keyword the Nihilist cipher addresses both weaknesses of the Polybius Square. Second,В no number in an encrypted message will exceed 66. First, it is susceptible to frequency analysis. The Polybius Square has obvious weaknesses. Repeat with the next letter of the ciphertext message. Use the Polybius square to determine the plaintext equivalent ofВ 31 (M) in first box of line 5.Д¦. Subtract theВ Additive from the Ciphertext (47-16) to determine the Polybius value (31) in first box of line 4.ДҐ. Enter the Polybius equivalent (or Additive) of F (16) in first box of line 3.Д¤. Enter the first letter of the keyword (F) in the first box of line 2.ДЈ. Enter the first number of the ciphertext message (47) in the first box of line 1.Дў. Follow the steps listed below to encrypt a message.ДЇigure 4: Message decrypted using the Nihilist cipherДЎ. You can view and print an encryption worksheet for this exercise by clicking here. With any cipher, encryption and decryption is easiest using a worksheet designed especially for the purpose. These numbers are then added (Figure 3) to generate the ciphertext.

POLYBIUS SQUARE DECODER SERIES

The original Nihilist cipher uses the Polybius square to convert both the plaintext and a keyword to a series of two-digit numbers. The term Nihilist cipher is sometimes extended to include several improved algorithms used much later for communication by the Soviet First Chief Directorate (KGB) with itsВ spies. To protect themselves from the Okhrana, the Czar's secret police, the Nihilists developed their own cipher based on the Polybius Square and a keyword. Lacking the ideology of Marx and the iron discipline of Lenin, they were never as well organized as the Bolesheviks. The Nihilists were a group ofВ anti-czarists who, in the 1880s, sought to overthrow the Russian monarchyВ by means of sabotage, terrorism and assassination. Thus 'MEET' is enciphered asВ 31-15-15-42.ДЇigure 2: Message enciphered with Polybius Square Each letter and number isВ represented by its co-ordinates in the grid.

POLYBIUS SQUARE DECODER PLUS

The 6 x 6 grid in Figure 1, for example,В represents all the letters of the alphabet plus all the numbers using two-letter combinations of the numbers 1 through 6. He designed the cipher bearing his nameВ to fractionate plaintext characters so that they can be represented by a smaller set of symbols. Polybius was an ancient Greek historian and scholar. The plaintext is used as input to an encryption algorithm. Plaintext (PT): In cryptography, plaintext (also called cleartext) is the information which the sender wishes to transmit to the receiver.

In encryption, the key specifies a particular transformation of plaintext into ciphertext, or vice versa during decryption. Without the key, an algorithm will have no result. Key (keyword, keytext): in cryptography, the key is a piece of information (a parameter) that determines the functional output of a cryptographic algorithm or cipher. In this exercise the student will learn to encrypt and decrypt messages using both the Polybius Square and the Nihilist ciphers.Д¬iphertext (CT): theВ encrypted version of a message that the sender wishes to transmit to the receiver.Дecipher (decrypt, decode): to convertВ a ciphertext message to plain text.Д®ncipher (encrypt, encode): to convertВ a plaintext messageВ to ciphertext.ДЇractionate: to divide or separate into parts break up This exercise demonstrates how an ancient cipher (the Polybius Square) was modified to createВ a classic field cipher - the Nihilist cipher. Laboratory Session 9: THE NIHILIST CIPHER

Polybius square decoder