From 423f24e9a182e986aeca404d80b3f9f469d80960 Mon Sep 17 00:00:00 2001
From: Daniel <59575049+lumijiez@users.noreply.github.com>
Date: Wed, 4 Dec 2024 00:30:56 +0200
Subject: [PATCH] des key schedule for lab

---
 src/main/java/org/lumijiez/DES.java | 89 +++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 src/main/java/org/lumijiez/DES.java

diff --git a/src/main/java/org/lumijiez/DES.java b/src/main/java/org/lumijiez/DES.java
new file mode 100644
index 0000000..f4ae25c
--- /dev/null
+++ b/src/main/java/org/lumijiez/DES.java
@@ -0,0 +1,89 @@
+package org.lumijiez;
+
+import java.util.Scanner;
+import java.util.Random;
+
+public class DES {
+    private static final int[] SHIFT_TABLE = {
+            1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
+    };
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.println("DES Key Schedule Calculator - Ci and Di Generation");
+        System.out.println("-----------------------------------------------");
+
+        System.out.println("Choose input method:");
+        System.out.println("1. Random generation");
+        System.out.println("2. Manual input");
+        int choice = scanner.nextInt();
+
+        String kPlus;
+
+        if (choice == 1) {
+            kPlus = generateRandomBits(56);
+        } else {
+            System.out.println("Enter 56-bit K+ (0s and 1s only):");
+            kPlus = scanner.next();
+
+            if (!kPlus.matches("[01]{56}")) {
+                System.out.println("Invalid input! Please enter exactly 56 bits (0s and 1s only)");
+                return;
+            }
+        }
+
+        System.out.println("Enter round number i (1-16):");
+        int round = scanner.nextInt();
+
+        if (round < 1 || round > 16) {
+            System.out.println("Invalid round number! Must be between 1 and 16");
+            return;
+        }
+
+        String c0 = kPlus.substring(0, 28);
+        String d0 = kPlus.substring(28, 56);
+
+        System.out.println("\nInitial values:");
+        System.out.println("K+ = " + kPlus);
+        System.out.println("C0 = " + c0);
+        System.out.println("D0 = " + d0);
+
+        String ci = c0;
+        String di = d0;
+
+        System.out.println("\nCalculating shifts for round " + round + ":");
+
+        for (int j = 0; j < round; j++) {
+            int shifts = SHIFT_TABLE[j];
+
+            ci = leftCircularShift(ci, shifts);
+            di = leftCircularShift(di, shifts);
+
+            System.out.println("\nRound " + (j + 1) + ":");
+            System.out.println("Number of left shifts: " + shifts);
+            System.out.println("C" + (j + 1) + " = " + ci);
+            System.out.println("D" + (j + 1) + " = " + di);
+        }
+
+        System.out.println("\nFinal Result for round " + round + ":");
+        System.out.println("C" + round + " = " + ci);
+        System.out.println("D" + round + " = " + di);
+    }
+
+    private static String leftCircularShift(String bits, int positions) {
+        positions = positions % bits.length();
+        return bits.substring(positions) + bits.substring(0, positions);
+    }
+
+    private static String generateRandomBits(int length) {
+        Random random = new Random();
+        StringBuilder sb = new StringBuilder(length);
+
+        for (int i = 0; i < length; i++) {
+            sb.append(random.nextInt(2));
+        }
+
+        return sb.toString();
+    }
+}