testing

Data-Encryption-Standard/README.md

@@ -0,0 +1,16 @@
+# DES Encryption Algorithm
+
+## Description
+This project implements a simplified version of the DES encryption algorithm, with encryption and decryption using a symmetric key.
+
+## How to Build
+1. Navigate to the `build` directory.
+2. Run `make` to compile the project.
+
+## How to Run
+1. After building, run the `des` executable using `./des`.
+2. You will be prompted to enter a message and a key, both as integers (64-bit).
+
+## How to Clean
+- Run `make clean` to remove all compiled files.
+

Data-Encryption-Standard/build/Makefile

@@ -0,0 +1,28 @@
+# Variables
+CC = gcc
+CFLAGS = -I../include -Wall -Wextra
+OBJDIR = ../obj
+SRCDIR = ../src
+BINDIR = ../build
+
+# Source files
+SOURCES = $(SRCDIR)/main.c $(SRCDIR)/des.c
+OBJECTS = $(OBJDIR)/main.o $(OBJDIR)/des.o
+
+# Build target
+TARGET = des
+
+# Rules
+all: $(BINDIR)/$(TARGET)
+
+$(BINDIR)/$(TARGET): $(OBJECTS)
+	$(CC) $(OBJECTS) -o $(BINDIR)/$(TARGET)
+
+$(OBJDIR)/%.o: $(SRCDIR)/%.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm -f $(OBJDIR)/*.o $(BINDIR)/$(TARGET)
+
+.PHONY: all clean
+

Data-Encryption-Standard/include/des.h

@@ -0,0 +1,7 @@
+#ifndef DES_H
+#define DES_H
+
+void des_encrypt(unsigned long long *message, unsigned long long key);
+void des_decrypt(unsigned long long *message, unsigned long long key);
+
+#endif // DES_H

Data-Encryption-Standard/src/des.c

@@ -0,0 +1,76 @@
+#include "des.h"
+#include <stdio.h>
+#include <stdint.h>
+
+// A simplified placeholder for the Initial Permutation
+static uint64_t initial_permutation(uint64_t message) {
+    // Apply an initial permutation (just a placeholder for now)
+    return message;  // In a real implementation, this would rearrange the bits
+}
+
+// A simplified placeholder for the Final Permutation
+static uint64_t final_permutation(uint64_t message) {
+    // Apply the final permutation (just a placeholder for now)
+    return message;  // In a real implementation, this would rearrange the bits
+}
+
+// A simplified placeholder for the Feistel function used in DES rounds
+static uint32_t feistel_function(uint32_t half_block, uint64_t subkey) {
+    // Apply an expansion, substitution, and permutation (placeholder)
+    return half_block ^ (uint32_t)(subkey);  // Simplified XOR with the key
+}
+
+// A simplified function to split the message into left and right halves
+static void split_message(uint64_t message, uint32_t *left, uint32_t *right) {
+    *left = (uint32_t)(message >> 32);
+    *right = (uint32_t)(message & 0xFFFFFFFF);
+}
+
+// A simplified function to merge left and right halves into one message
+static uint64_t merge_message(uint32_t left, uint32_t right) {
+    return ((uint64_t)left << 32) | (uint64_t)right;
+}
+
+// The main DES encryption function
+void des_encrypt(unsigned long long *message, unsigned long long key) {
+    // Apply the initial permutation
+    *message = initial_permutation(*message);
+
+    uint32_t left, right;
+    split_message(*message, &left, &right);
+
+    // Perform 16 rounds of the Feistel function (simplified for now)
+    for (int i = 0; i < 16; i++) {
+        uint32_t temp = right;
+        right = left ^ feistel_function(right, key);  // Simplified function
+        left = temp;
+    }
+
+    // Merge the halves back together
+    *message = merge_message(left, right);
+
+    // Apply the final permutation
+    *message = final_permutation(*message);
+}
+
+// The main DES decryption function (similar to encryption, but reverse)
+void des_decrypt(unsigned long long *message, unsigned long long key) {
+    // Apply the initial permutation
+    *message = initial_permutation(*message);
+
+    uint32_t left, right;
+    split_message(*message, &left, &right);
+
+    // Perform 16 rounds of the Feistel function (reversed for decryption)
+    for (int i = 0; i < 16; i++) {
+        uint32_t temp = left;
+        left = right ^ feistel_function(left, key);  // Simplified function
+        right = temp;
+    }
+
+    // Merge the halves back together
+    *message = merge_message(left, right);
+
+    // Apply the final permutation
+    *message = final_permutation(*message);
+}

Data-Encryption-Standard/src/main.c

@@ -0,0 +1,25 @@
+#include "des.h"
+#include <stdio.h>
+
+int main() {
+    unsigned long long message;
+    unsigned long long key;
+
+    // Ask for a message and key (both as integers for simplicity)
+    printf("Enter a message to encrypt (as a 64-bit integer): ");
+    scanf("%llu", &message);
+
+    printf("Enter a key (as a 64-bit integer): ");
+    scanf("%llu", &key);
+
+    // Encrypt the message
+    des_encrypt(&message, key);
+    printf("Encrypted message: %llu\n", message);
+
+    // Decrypt the message
+    des_decrypt(&message, key);
+    printf("Decrypted message: %llu\n", message);
+
+    return 0;
+}
+