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• Caesar Cipher Decryption
• Caesar Cipher Program In Java

Simple Chat Room using Python. Socket Programming in Java. Text: ATTACKATONCE Shift: 4 Cipher: EXXEGOEXSRGI. Algorithm for Caesar Cipher: Input: A String of lower case letters, called Text.

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What is a Caesar cipher? A Caesar cipher works by moving the letters in the alphabet by a certain number called the offset. If I encrypt the letter ‘A’ using an offset of 3 then ‘A’ becomes ‘D’. The rotation loops around the alaphabet so the letter ‘Z’ would become ‘C’ with an offset of 3. Patterns in a language A language has certain patterns in the writing, for example in English the letter ‘E’ will appear more often than the letter ‘Z’ so these pattersn can be used to try and work out the rotation. The program I developed uses a text file called ‘quadgrams’ which contains a block of four letters with the number of occurances in a piece of text.

Caesar Cipher Decryption

Brief description of the program The program takes in a piece of encrypted text and changes the offset all the way up to 25 and for each offset it passes it to a method that works out the mathematical probability that the piece of text is now English with that offset. To work out the mathematical probability it loads the quadgrams text file into a HashMap and searches the map for quadgrams that appear in the cipered text. It then stores the overall probability for that particular offset, moves to the next offset and repeats, if the probability is higher than the previous offset then this offset and probability is stored. See flow diagram below! CCDT Flow Chart Disclaimer: You can use this code anyway you like but you must provide acknowledgement to Monotok.org/Christopher Hamer.

Caesar Cipher Program In Java

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