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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 ...
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 ...
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 ...
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 ...
t. e. In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by ...
In cryptography, a transposition cipher (also known as a permutation cipher) is a method of encryption which scrambles the positions of characters ( transposition) without changing the characters themselves. Transposition ciphers reorder units of plaintext (typically characters or groups of characters) according to a regular system to produce a ...
John Playfair FRSE, FRS (10 [citation needed] March 1748 – 20 July 1819) was a Church of Scotland minister, remembered as a scientist and mathematician, and a professor of natural philosophy at the University of Edinburgh. He is best known for his book Illustrations of the Huttonian Theory of the Earth (1802), which summarised the work of ...
Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. This process prevents the loss of sensitive information via hacking. Decryption, the inverse of encryption, is the process of turning ciphertext into ...