Columnar Transposition Cipher - GeeksforGeeks (2024)

// CPP program for illustrating// Columnar Transposition Cipher#include <bits/stdc++.h>using namespace std;// Encription functionstring Encryption(int no_rows, int len_key, int len_msg, string msg, int col_val[]){ int x = 0; char enc_mat[no_rows + 1][len_key]; // creating the matrix for (int i = 0; i < no_rows + 1; i++) { for (int j = 0; j < len_key; j++) { // initializes the positions with '_' after the // end of message if (x >= len_msg) { enc_mat[i][j] = '_'; } else { enc_mat[i][j] = msg[x]; } x++; } } int t = 1; string cipher = ""; // finding the cipher text according to the value of // col_val matrix while (t <= len_key) { for (int i = 0; i < len_key; i++) { int k = col_val[i]; if (k == t) { for (int j = 0; j < no_rows + 1; j++) { cipher += enc_mat[j][i]; } t++; } } } return cipher;}// decryption functionstring Decryption(int no_rows, int len_key, string cipher, int col_val[]){ char dec_mat[no_rows + 1][len_key]; int x = 0, t = 1; // rearrange the matrix according to the col_val while (t <= len_key) { for (int i = 0; i < len_key; i++) { int k = col_val[i]; if (k == t) { for (int j = 0; j < no_rows + 1; j++) { dec_mat[j][i] = cipher[x]; x++; } t++; } } } string message = ""; for (int i = 0; i < no_rows + 1; i++) { for (int j = 0; j < len_key; j++) { // replacing the '_' with space if (dec_mat[i][j] == '_') { dec_mat[i][j] = ' '; } message += dec_mat[i][j]; } } return message;}int main(){ // message string msg = "Geeks for Geeks"; // key string key = "HACK"; int len_key = key.length(); int len_msg = msg.length(); int val = 1, count = 0, ind; int col_val[len_key]; // intializing col_val matrix with 0 memset(col_val, 0, sizeof(col_val)); // numbering the key alphabets according to its ACII // value while (count < len_key) { int min = 999; for (int i = 0; i < len_key; i++) { if ((min > int(key[i])) && (col_val[i] == 0)) { min = int(key[i]); ind = i; } } col_val[ind] = val; count++; val++; } int no_rows = len_msg / len_key; // encrypted text string cipher_text = " "; cipher_text = Encryption(no_rows, len_key, len_msg, msg, col_val); cout << "Encrypted Message : " << cipher_text << endl; // decrypted text string original_msg = " "; original_msg = Decryption(no_rows, len_key, cipher_text, col_val); cout << "Decrypted Message : " << original_msg << endl;}// This code is contributed by Suchita Gond

import java.util.*;public class ColumnarTranspositionCipher { // Key for Columnar Transposition static final String key = "HACK"; static Map<Character, Integer> keyMap = new HashMap<>(); static void setPermutationOrder() { // Add the permutation order into the map for (int i = 0; i < key.length(); i++) { keyMap.put(key.charAt(i), i); } } // Encryption static String encryptMessage(String msg) { int row, col; StringBuilder cipher = new StringBuilder(); /* Calculate the number of columns in the matrix */ col = key.length(); /* Calculate the maximum number of rows in the matrix */ row = (int) Math.ceil((double) msg.length() / col); char[][] matrix = new char[row][col]; for (int i = 0, k = 0; i < row; i++) { for (int j = 0; j < col; ) { if (k < msg.length()) { char ch = msg.charAt(k); if (Character.isLetter(ch) || ch == ' ') { matrix[i][j] = ch; j++; } k++; } else { /* Add padding character '_' */ matrix[i][j] = '_'; j++; } } } for (Map.Entry<Character, Integer> entry : keyMap.entrySet()) { int columnIndex = entry.getValue(); // Get the cipher text from the matrix column-wise using the permuted key for (int i = 0; i < row; i++) { if (Character.isLetter(matrix[i][columnIndex]) || matrix[i][columnIndex] == ' ' || matrix[i][columnIndex] == '_') { cipher.append(matrix[i][columnIndex]); } } } return cipher.toString(); } // Decryption static String decryptMessage(String cipher) { /* Calculate the number of columns for the cipher matrix */ int col = key.length(); int row = (int) Math.ceil((double) cipher.length() / col); char[][] cipherMat = new char[row][col]; /* Add characters into the matrix column-wise */ int k = 0; for (int j = 0; j < col; j++) { for (int i = 0; i < row; i++) { cipherMat[i][j] = cipher.charAt(k); k++; } } /* Update the order of the key for decryption */ int index = 0; for (Map.Entry<Character, Integer> entry : keyMap.entrySet()) { entry.setValue(index++); } /* Arrange the matrix column-wise according to the permutation order */ char[][] decCipher = new char[row][col]; for (int l = 0; l < key.length(); l++) { int columnIndex = keyMap.get(key.charAt(l)); for (int i = 0; i < row; i++) { decCipher[i][l] = cipherMat[i][columnIndex]; } } /* Get the message using the matrix */ StringBuilder msg = new StringBuilder(); for (int i = 0; i < row; i++) { for (int j = 0; j < col; j++) { if (decCipher[i][j] != '_') { msg.append(decCipher[i][j]); } } } return msg.toString(); } public static void main(String[] args) { /* Message */ String msg = "Geeks for Geeks"; setPermutationOrder(); // Calling encryption function String cipher = encryptMessage(msg); System.out.println("Encrypted Message: " + cipher); // Calling Decryption function System.out.println("Decrypted Message: " + decryptMessage(cipher)); }}

# Python3 implementation of# Columnar Transpositionimport mathkey = "HACK"# Encryptiondef encryptMessage(msg): cipher = "" # track key indices k_indx = 0 msg_len = float(len(msg)) msg_lst = list(msg) key_lst = sorted(list(key)) # calculate column of the matrix col = len(key) # calculate maximum row of the matrix row = int(math.ceil(msg_len / col)) # add the padding character '_' in empty # the empty cell of the matix fill_null = int((row * col) - msg_len) msg_lst.extend('_' * fill_null) # create Matrix and insert message and # padding characters row-wise matrix = [msg_lst[i: i + col] for i in range(0, len(msg_lst), col)] # read matrix column-wise using key for _ in range(col): curr_idx = key.index(key_lst[k_indx]) cipher += ''.join([row[curr_idx] for row in matrix]) k_indx += 1 return cipher# Decryptiondef decryptMessage(cipher): msg = "" # track key indices k_indx = 0 # track msg indices msg_indx = 0 msg_len = float(len(cipher)) msg_lst = list(cipher) # calculate column of the matrix col = len(key) # calculate maximum row of the matrix row = int(math.ceil(msg_len / col)) # convert key into list and sort # alphabetically so we can access # each character by its alphabetical position. key_lst = sorted(list(key)) # create an empty matrix to # store deciphered message dec_cipher = [] for _ in range(row): dec_cipher += [[None] * col] # Arrange the matrix column wise according # to permutation order by adding into new matrix for _ in range(col): curr_idx = key.index(key_lst[k_indx]) for j in range(row): dec_cipher[j][curr_idx] = msg_lst[msg_indx] msg_indx += 1 k_indx += 1 # convert decrypted msg matrix into a string try: msg = ''.join(sum(dec_cipher, [])) except TypeError: raise TypeError("This program cannot", "handle repeating words.") null_count = msg.count('_') if null_count > 0: return msg[: -null_count] return msg# Driver Codemsg = "Geeks for Geeks"cipher = encryptMessage(msg)print("Encrypted Message: {}". format(cipher))print("Decryped Message: {}". format(decryptMessage(cipher)))# This code is contributed by Aditya K

using System;using System.Collections.Generic;public class ColumnarTranspositionCipher { // Key for Columnar Transposition static readonly string key = "HACK"; static Dictionary<char, int> keyMap = new Dictionary<char, int>(); static void SetPermutationOrder() { // Add the permutation order into the dictionary for (int i = 0; i < key.Length; i++) { keyMap[key[i]] = i; } } // Encryption static string EncryptMessage(string msg) { int row, col; System.Text.StringBuilder cipher = new System.Text.StringBuilder(); /* Calculate the number of columns in the matrix */ col = key.Length; /* Calculate the maximum number of rows in the * matrix */ row = (int)Math.Ceiling((double)msg.Length / col); char[, ] matrix = new char[row, col]; for (int i = 0, k = 0; i < row; i++) { for (int j = 0; j < col;) { if (k < msg.Length) { char ch = msg[k]; if (char.IsLetter(ch) || ch == ' ') { matrix[i, j] = ch; j++; } k++; } else { /* Add padding character '_' */ matrix[i, j] = '_'; j++; } } } foreach( var entry in new Dictionary<char, int>(keyMap)) { int columnIndex = entry.Value; // Get the cipher text from the matrix // column-wise using the permuted key for (int i = 0; i < row; i++) { if (char.IsLetter(matrix[i, columnIndex]) || matrix[i, columnIndex] == ' ' || matrix[i, columnIndex] == '_') { cipher.Append(matrix[i, columnIndex]); } } } return cipher.ToString(); } // Decryption static string DecryptMessage(string cipher) { /* Calculate the number of columns for the cipher * matrix */ int col = key.Length; int row = (int)Math.Ceiling((double)cipher.Length / col); char[, ] cipherMat = new char[row, col]; /* Add characters into the matrix column-wise */ int k = 0; for (int j = 0; j < col; j++) { for (int i = 0; i < row; i++) { cipherMat[i, j] = cipher[k]; k++; } } /* Update the order of the key for decryption */ int index = 0; foreach( var entry in new Dictionary<char, int>(keyMap)) { keyMap[entry.Key] = index++; } /* Arrange the matrix column-wise according to the * permutation order */ char[, ] decCipher = new char[row, col]; foreach(var entry in keyMap) { int columnIndex = entry.Value; for (int i = 0; i < row; i++) { decCipher[i, columnIndex] = cipherMat[i, columnIndex]; } } /* Get the message using the matrix */ System.Text.StringBuilder msg = new System.Text.StringBuilder(); for (int i = 0; i < row; i++) { for (int j = 0; j < col; j++) { if (decCipher[i, j] != '_') { msg.Append(decCipher[i, j]); } } } return msg.ToString(); } public static void Main(string[] args) { /* Message */ string msg = "Geeks for Geeks"; SetPermutationOrder(); // Calling encryption function string cipher = EncryptMessage(msg); Console.WriteLine("Encrypted Message: " + cipher); // Calling Decryption function Console.WriteLine("Decrypted Message: " + DecryptMessage(cipher)); }}

// JavaScript implementation of // Columnar Transpositionconst key = "HACK";// Encryptionfunction encryptMessage(msg) { let cipher = ""; // track key indices let k_indx = 0; const msg_len = msg.length; const msg_lst = Array.from(msg); const key_lst = Array.from(key).sort(); // calculate column of the matrix const col = key.length; // calculate maximum row of the matrix const row = Math.ceil(msg_len / col); // add the padding character '_' in empty // the empty cell of the matrix const fill_null = (row * col) - msg_len; for (let i = 0; i < fill_null; i++) { msg_lst.push('_'); } // create Matrix and insert message and // padding characters row-wise const matrix = []; for (let i = 0; i < msg_lst.length; i += col) { matrix.push(msg_lst.slice(i, i + col)); } // read matrix column-wise using key for (let _ = 0; _ < col; _++) { const curr_idx = key.indexOf(key_lst[k_indx]); for (const row of matrix) { cipher += row[curr_idx]; } k_indx++; } return cipher;}// Decryptionfunction decryptMessage(cipher) { let msg = ""; // track key indices let k_indx = 0; // track msg indices let msg_indx = 0; const msg_len = cipher.length; const msg_lst = Array.from(cipher); // calculate column of the matrix const col = key.length; // calculate maximum row of the matrix const row = Math.ceil(msg_len / col); // convert key into list and sort  // alphabetically so we can access  // each character by its alphabetical position. const key_lst = Array.from(key).sort(); // create an empty matrix to  // store deciphered message const dec_cipher = []; for (let i = 0; i < row; i++) { dec_cipher.push(Array(col).fill(null)); } // Arrange the matrix column wise according  // to permutation order by adding into a new matrix for (let _ = 0; _ < col; _++) { const curr_idx = key.indexOf(key_lst[k_indx]); for (let j = 0; j < row; j++) { dec_cipher[j][curr_idx] = msg_lst[msg_indx]; msg_indx++; } k_indx++; } // convert decrypted msg matrix into a string try { msg = dec_cipher.flat().join(''); } catch (err) { throw new Error("This program cannot handle repeating words."); } const null_count = (msg.match(/_/g) || []).length; if (null_count > 0) { return msg.slice(0, -null_count); } return msg;}// Driver Codeconst msg = "Geeks for Geeks";const cipher = encryptMessage(msg);console.log("Encrypted Message: " + cipher);console.log("Decrypted Message: " + decryptMessage(cipher));// This code is contributed by phasing17