Completed Custom encrypt

Cryptography-CSS/CustomEncryption.java

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+import java.util.*;
+import java.io.*;
+import java.security.MessageDigest;
+
+
+class CustomEncryption {
+    public static String esc = "~~";
+
+    public static String Encrypt(String pt, int k[]) {
+        int scaleKey;
+        int n;
+        String ct = "";
+
+        String hashValue = getHash(pt);
+        System.out.println("Message Digest: " + hashValue);
+
+        ct += hashValue;
+        ct += esc;
+        ct += pt;
+
+        n = ct.length();
+        System.out.println("length: " + n);        
+
+        char[] ctArr = ct.toCharArray();
+        double scale = n / 10;
+        for (int i = 0; i < k.length; i++) {
+            scaleKey = (int)(k[i] * scale);
+            int index = 0;
+            for (int j = 0; j < scaleKey; j++) {
+                index += scaleKey;
+                for (int m = 0; m < k.length; m++) {
+                    ctArr[(index+m) % ctArr.length] += scaleKey;
+                    ctArr[(index+m) % ctArr.length] %= 256;
+                }
+            }
+        }
+
+        return String.valueOf(ctArr);
+    }
+
+    public static String Decrypt(String ct, int k[]) {
+        int n = ct.length(), scaleKey;
+        String pt = "";
+        System.out.println("length: " + n);
+
+        double scale = n / 10;
+        char[] ctArr = ct.toCharArray();
+        for (int i = 0; i < k.length; i++) {
+            scaleKey = (int)(k[i] * scale);
+            int index = 0;
+            for (int j = 0; j < scaleKey; j++) {
+                index += scaleKey;
+                for (int m = 0; m < k.length; m++) {
+                    ctArr[(index+m) % ctArr.length] -= scaleKey;
+                    ctArr[(index+m) % ctArr.length] %= 256;
+                }
+            }
+        }
+        ct = String.valueOf(ctArr);
+
+        for (int i = 0; i < ct.length(); i++) {
+            if (ct.charAt(i) == '~' && ct.charAt(i) == ct.charAt(i-1)) {
+                String hashValue = ct.substring(0, i-1);
+                System.out.println("Message Digest: " + hashValue);
+                pt = ct.substring(i+1, n);
+                System.out.println("Hash of message: " + getHash(pt));
+                System.out.println("Is Message Digest equal to Hash? " + hashValue.equals(getHash(pt)));
+                break;
+            }
+        }    
+
+        return pt;
+    }
+
+    public static String getHash(String data) {
+        String result = null;
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            byte[] hash = digest.digest(data.getBytes("UTF-8"));
+            return Base64.getEncoder().encodeToString(hash);
+        }catch(Exception ex) {
+            ex.printStackTrace();
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        String pt = "", ct;
+        int[] k = new int[]{3, 1, 2, 7, 5, 2, 8, 4, 9, 6, 7}; 
+        Scanner sc = new Scanner(System.in);
+
+        System.out.print("Enter plaintext: ");        
+        pt = sc.nextLine(); 
+
+        System.out.println("\nEncrypting");
+        ct = Encrypt(pt, k);
+        System.out.println("Cipher text: " + ct);
+
+        System.out.println("\nDecrypting");
+        pt = Decrypt(ct, k);
+        System.out.println("Plain text: " + pt);
+    }
+}