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Playfair cipher. The Playfair cipher uses a 5×5 grid of letters, and encrypts a message by breaking the text into pairs of letters and swapping them according to their positions in a rectangle within that grid: "HI" becomes "BM". The Playfair cipher or Playfair square or Wheatstone–Playfair cipher is a manual symmetric encryption technique ...
The Two-square cipher, also called double Playfair, is a manual symmetric encryption technique. [1] It was developed to ease the cumbersome nature of the large encryption/decryption matrix used in the four-square cipher while still being slightly stronger than the single-square Playfair cipher . The technique encrypts pairs of letters ...
In cryptanalysis, frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers . Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters ...
1854 – Charles Wheatstone invents Playfair cipher; c. 1854 – Babbage's method for breaking polyalphabetic ciphers (pub 1863 by Kasiski) 1855 – For the English side in Crimean War, Charles Babbage broke Vigenère's autokey cipher (the 'unbreakable cipher' of the time) as well as the much weaker cipher that is called Vigenère cipher today ...
Index of coincidence. In cryptography, coincidence counting is the technique (invented by William F. Friedman [ 1]) of putting two texts side-by-side and counting the number of times that identical letters appear in the same position in both texts. This count, either as a ratio of the total or normalized by dividing by the expected count for a ...
Download Desktop Gold. AOL Desktop Gold is included at no additional cost with your membership. 2. Under 'All Products' scroll to 'AOL Desktop Gold'. If you have an AOL Desktop Gold trial or subscription. Using the link in the Official AOL signup confirmation email you received. 1.
Polygraphic substitution cipher: the unit of substitution is a sequence of two or more letters rather than just one (e.g., Playfair cipher) Transposition cipher: the ciphertext is a permutation of the plaintext (e.g., rail fence cipher) Historical ciphers are not generally used as a standalone encryption technique because they are quite easy to ...
Félix Delastelle. Félix-Marie Delastelle (2 January 1840 – 2 April 1902) was a French cryptographer, best known for inventing the bifid cipher, [1] first presented in the Revue du Génie civil in 1895 under the name of "cryptographie nouvelle". This cipher combines fractionation with transposition, and was an early cipher to implement the ...