Added Column transposition Cipher in Java

pooja2405 · web-flow · commit 8267fb2a39fc · 2020-10-02T21:34:30.000+05:30
The Columnar Transposition Cipher is a form of transposition cipher just like Rail Fence Cipher. Columnar Transposition involves writing the plaintext out in rows, and then reading the ciphertext off in columns one by one.
diff --git a/ColumnarTranspositionCipher.java b/ColumnarTranspositionCipher.java
@@ -0,0 +1,125 @@
+import java.io.*;
+class Columnar {
+    char arr[][], encrypt[][], decrypt[][], keya[], keytemp[];
+
+    void createMatrixEncrypt(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] = ' ';
+                }
+            }
+        }
+    }
+
+    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;
+                }
+            }
+        }
+    }
+
+    void createMatrixDecrypt(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] = ' ';
+                }
+            }
+        }
+    }
+
+    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;
+                }
+            }
+        }
+    }
+
+    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;
+                }
+            }
+        }
+    }
+
+    void resultEncrypt(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]);
+            }
+        }
+    }
+
+    void resultDecrypt(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;
+        Columnar obj = new Columnar();
+        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();
+        if (choice == 1) {
+            obj.createMatrixEncrypt(s, key, row, column);
+            obj.createkey(key, column);
+            obj.encrypt(row, column);
+            obj.resultEncrypt(row, column, obj.encrypt);
+        } else {
+            obj.createMatrixDecrypt(s, key, row, column);
+            obj.createkey(key, column);
+            obj.decrypt(row, column);
+            obj.resultDecrypt(row, column, obj.decrypt);
+        }
+
+    }
+}
