Type the text to encode: meetmeatthecafeonmainstreettomorrowatnoon Using the example with Alice and Bob we get this output. String encipheredText = encipher.DoCipher() ĭecipher decipher = new Decipher(encipheredText, key) Ĭonsole.WriteLine(decipher.DoDecipher()) The Cipher class is pretty straight forward but we’ll take a look at a few things.Ĭonsole.Write("Type the text to encode: ") Įncipher encipher = new Encipher(clearText, key) Public void PrintGrid(bool printHeader = false)įor (int j = 0 j < Grid.GetLength(Column) j++)Ĭonsole.WriteLine("+".PadRight(Key.Length * 2, '-') + "+") Internal string GetColumnText(int column)įor (int i = 0 i < Grid.GetLength(Row) i++) Return (char) new Random().Next(CHAR_A, CHAR_Z + 1) Internal char GetChar(string text, int stringPosition) Regex.IsMatch(Key, VALID_KEY_CHARACTERS) "characters, and can't contain duplicate characters.")
The key must be at least 2 characters, only use alphanumeric " + Private const string VALID_KEY_CHARACTERS = "^ is not a valid key.
#Transposition cipher code
The code consists of three classes, Encipher, Decipher, and an abstract class Cipher that they inherit common and helper methods from. The following example is written in C# but should be pretty easy to rewrite into any other object oriented language. After the columns have been filled in, the matrix will look like the example above and Bob can read the message in clear text line by line. The encrypted message would then look like this: ttfaroooe etamttrnp meeoneoan mheiemwoq eacnstrtsĪlice then sends this encrypted message to Bob who reconstructs the matrix, using the same key, by filling in the columns in the key’s lexicographical order. With this key would be in the order of E, I, Q, T, and U. Next Alice write out the columns in lexicographical order based on the key. The letters at the end are randomized to to pad the matrix. Next step is to create the matrix based on their key. She then writes her message “meet me at the cafe on main street tomorrow at noon”. They’ve previously decided on a shared key, QUIET. Let’s say that Alice wants to send Bob a message about a secret meeting place. Today I thought we could talk a little bit about Columnar Transposition Ciphers (hereby called CTC for short), let’s start with discussing what a CTC is.Ī CTC is a simple encryption method using a shared key between the participants, where the characters in a clear text message gets shifted around in a specific predetermined way in a matrix.
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