ColumnarCipher.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * @author arthur.paixao
 * @category Columnar Cipher Encode/Decode
 */
public class ColumnarCipher {
	char arr[][], encrypt[][], decrypt[][], keya[], keytemp[];

	public void creatematrixE(String s, String key, int row, int column) {
		arr = new char[row][column];
		int k = 0;
		keya = key.toCharArray();
		for (int i = 0; i < row; i++) {
			for (int j = 0; j < column; j++) {
				if (k < s.length()) {
					arr[i][j] = s.charAt(k);
					k++;
				} else {
					arr[i][j] = ' ';
				}
			}
		}
	}

	public void createkey(String key, int column) {
		keytemp = key.toCharArray();
		for (int i = 0; i < column - 1; i++) {
			for (int j = i + 1; j < column; j++) {
				if (keytemp[i] > keytemp[j]) {
					char temp = keytemp[i];
					keytemp[i] = keytemp[j];
					keytemp[j] = temp;
				}
			}
		}
	}

	public void creatematrixD(String s, String key, int row, int column) {
		arr = new char[row][column];
		int k = 0;
		keya = key.toCharArray();
		for (int i = 0; i < column; i++) {
			for (int j = 0; j < row; j++) {
				if (k < s.length()) {
					arr[j][i] = s.charAt(k);
					k++;
				} else {
					arr[j][i] = ' ';
				}
			}
		}
	}

	public void encrypt(int row, int column) {
		encrypt = new char[row][column];
		for (int i = 0; i < column; i++) {
			for (int j = 0; j < column; j++) {
				if (keya[i] == keytemp[j]) {
					for (int k = 0; k < row; k++) {
						encrypt[k][j] = arr[k][i];
					}
					keytemp[j] = '?';
					break;
				}
			}
		}
	}

	public void decrypt(int row, int column) {
		decrypt = new char[row][column];
		for (int i = 0; i < column; i++) {
			for (int j = 0; j < column; j++) {
				if (keya[j] == keytemp[i]) {
					for (int k = 0; k < row; k++) {
						decrypt[k][j] = arr[k][i];
					}
					keya[j] = '?';
					break;
				}
			}
		}
	}

	public void resultE(int row, int column, char arr[][]) {
		System.out.println("Result:");
		for (int i = 0; i < column; i++) {
			for (int j = 0; j < row; j++) {
				System.out.print(arr[j][i]);
			}
		}
	}

	public void resultD(int row, int column, char arr[][]) {
		System.out.println("Result:");
		for (int i = 0; i < row; i++) {
			for (int j = 0; j < column; j++) {
				System.out.print(arr[i][j]);
			}
		}
	}

	public static void main(String args[]) throws IOException {
		int row, column, choice;
		ColumnarCipher obj = new ColumnarCipher();
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		System.out.println("Menu:\n1) Encryption\n2) Decryption");
		choice = Integer.parseInt(in.readLine());
		System.out.println("Enter the string:");
		String s = in.readLine();
		System.out.println("Enter the key:");
		String key = in.readLine();
		row = s.length() / key.length();
		if (s.length() % key.length() != 0)
			row++;
		column = key.length();
		switch (choice) {
		case 1:
			obj.creatematrixE(s, key, row, column);
			obj.createkey(key, column);
			obj.encrypt(row, column);
			obj.resultE(row, column, obj.encrypt);
			break;
		case 2:
			obj.creatematrixD(s, key, row, column);
			obj.createkey(key, column);
			obj.decrypt(row, column);
			obj.resultD(row, column, obj.decrypt);
			break;
		}
	}

}