package Ciphers.Substitution; import java.util.*; public class PlayfairCipher { private static final String letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter plain text: "); String plainText = scanner.nextLine().toUpperCase(); System.out.print("Enter key: "); String key = scanner.nextLine().toUpperCase(); String[][] cipherMatrix = getCipherMatrix(key); String cipherText = encrypt(cipherMatrix, plainText); System.out.println("cipherText = " + cipherText); } private static String encrypt(String[][] cipherMatrix, String plainText) { if (plainText.length() % 2 != 0) { plainText += "X"; } List pairs = new ArrayList<>(); for (int i = 0; i < plainText.length(); i += 2) { pairs.add(plainText.substring(i, i + 2)); } Map cipherMap = new HashMap<>(); for (int i = 0; i < 5; i++) { for (int j = 0; j < 5; j++) { cipherMap.put(cipherMatrix[i][j].charAt(0), new int[]{i, j}); if (cipherMatrix[i][j].equals("I")) { cipherMap.put('J', new int[]{i, j}); } } } StringBuilder cipherText = new StringBuilder(); for (String pair : pairs) { int[] pos1 = cipherMap.get(pair.charAt(0)); int[] pos2 = cipherMap.get(pair.charAt(1)); if (pos1[0] == pos2[0]) { cipherText.append(cipherMatrix[pos1[0]][(pos1[1] + 1) % 5]); cipherText.append(cipherMatrix[pos2[0]][(pos2[1] + 1) % 5]); } else if (pos1[1] == pos2[1]) { cipherText.append(cipherMatrix[(pos1[0] + 1) % 5][pos1[1]]); cipherText.append(cipherMatrix[(pos2[0] + 1) % 5][pos2[1]]); } else { cipherText.append(cipherMatrix[pos1[0]][pos2[1]]); cipherText.append(cipherMatrix[pos2[0]][pos1[1]]); } } return cipherText.toString(); } private static String[][] getCipherMatrix(String key) { List cipherMatrix = new ArrayList<>(); for (String k : key.concat(letters).split("")) { if (k.equals("J")) { k = "I"; } if (!cipherMatrix.contains(k)) { cipherMatrix.add(k); } } String[][] cipherMatrix2D = new String[5][5]; for (int i = 0; i < 5; i++) { for (int j = 0; j < 5; j++) { cipherMatrix2D[i][j] = cipherMatrix.get(i * 5 + j); } } return cipherMatrix2D; } }

Fire

Cite