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This method ensures that each letter in the plaintext is substituted by a different letter in the ciphertext. If any letters overlap at the end of the alphabet, such as Z-Z or X-X, they are repositioned to maintain the cipher's security and adhere to guidelines established by the American Cryptogram Association [1].
In the 2000s, security questions came into widespread use on the Internet. [1] As a form of self-service password reset, security questions have reduced information technology help desk costs. [1] By allowing the use of security questions online, they are rendered vulnerable to keystroke logging and brute-force guessing attacks, [3] as well as ...
All spaces and repeated letters are removed from a word or phrase, which the encoder then uses as the start of the cipher alphabet. The end of the cipher alphabet is the rest of the alphabet in order without repeating the letters in the keyword. For example, if the keyword is CIPHER, the cipher alphabet would look like this:
It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. [1] The method is named after Julius Caesar, who used it in his private correspondence.
The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that each letter encrypts to one other letter, and back again, meaning the cipher is essentially a ...
The California Job Case was a compartmentalized box for printing in the 19th century, sizes corresponding to the commonality of letters. The frequency of letters in text has been studied for use in cryptanalysis, and frequency analysis in particular, dating back to the Arab mathematician al-Kindi (c. AD 801–873 ), who formally developed the method (the ciphers breakable by this technique go ...
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The two letters of the digram are considered opposite corners of a rectangle in the key table. To perform the substitution, apply the following 4 rules, in order, to each pair of letters in the plaintext: If both letters are the same (or only one letter is left), add an "X" after the first letter. Encrypt the new pair and continue.