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  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. #define MAX_INPUT_LENGTH 50
  5. // Kunci rahasia yang telah di-XOR 0x77 (dibuat saat kompilasi)
  6. // Aslinya: "ADVANCED_RE_CHALLENGE"
  7. const char encrypted_key[] = "\x26\x31\x32\x35\x36\x37\x32\x35\x33\x34\x33\x37\x30\x32\x35\x37\x37\x32\x34\x37\x32";
  8. const int KEY_LENGTH = 21;
  9. const char MAGIC_BYTE = 0x77; // Kunci enkripsi (XOR key)
  10.  
  11. // Fungsi untuk mengenkripsi/mendekripsi string menggunakan XOR
  12. void simple_xor(char *data, int len, char key) {
  13.     for (int i = 0; i < len; i++) {
  14.         data[i] = data[i] ^ key;
  15.     }
  16. }
  17.  
  18. // Fungsi pengecekan yang kompleks
  19. int check_serial(const char *input) {
  20.     if (strlen(input) != KEY_LENGTH) {
  21.         return 0; // Gagal jika panjang berbeda
  22.     }
  23.  
  24.     // Buat salinan input karena kita akan memodifikasinya
  25.     char temp_input[MAX_INPUT_LENGTH];
  26.     strncpy(temp_input, input, KEY_LENGTH);
  27.     temp_input[KEY_LENGTH] = '\0'; // Pastikan null-terminated
  28.  
  29.     // Langkah 1: Enkripsi input pengguna (teknik pengalihan perhatian)
  30.     // Mahasiswa harus menyadari bahwa input mereka diubah
  31.     simple_xor(temp_input, KEY_LENGTH, MAGIC_BYTE);
  32.  
  33.     // Langkah 2: Perbandingan dengan kunci yang sudah terenkripsi
  34.     // Perbandingan dilakukan pada hasil XOR, bukan pada kunci asli
  35.     if (memcmp(temp_input, encrypted_key, KEY_LENGTH) == 0) {
  36.         return 1; // Berhasil
  37.     } else {
  38.         return 0; // Gagal
  39.     }
  40. }
  41.  
  42. int main() {
  43.     char user_input[MAX_INPUT_LENGTH];
  44.  
  45.     printf("--- Challenge Reversing Lanjutan ---\n");
  46.     printf("Masukkan Serial Key (tepat %d karakter): ", KEY_LENGTH);
  47.  
  48.     if (fgets(user_input, MAX_INPUT_LENGTH, stdin) != NULL) {
  49.         size_t len = strlen(user_input);
  50.         if (len > 0 && user_input[len - 1] == '\n') {
  51.             user_input[len - 1] = '\0';
  52.         }
  53.  
  54.         if (check_serial(user_input)) {
  55.             printf("\n[SUCCESS] Kode Lanjutan Ditembus!\n");
  56.             // String FLAG disembunyikan di sini
  57.             printf("FLAG: {XOR_IS_FUN_BUT_TRICKY}\n");
  58.         } else {
  59.             printf("\n[FAILURE] Serial Key salah. Coba lagi.\n");
  60.         }
  61.     }
  62.  
  63.     return 0;
  64. }
Success #stdin #stdout 0s 5332KB
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stdin
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/*  Berechnung des Hamming-Abstandes zwischen zwei 128-Bit Werten in 	*/
/*	einer Textdatei. 													*/
/*  Die Werte müssen auf einer separaten Zeile gespeichert sein			*/
/* 																		*/
/*	Erstellt: 17.5.2010													*/
/*  Autor: Thomas Scheffler												*/

#include <stdio.h>
#include <stdlib.h>

#define ARRAY_SIZE 32

unsigned Hamdist(unsigned x, unsigned y)
{
  unsigned dist = 0, val = x ^ y;
 
  // Count the number of set bits
  while(val)
  {
    ++dist; 
    val &= val - 1;
  }
 
  return dist;
}



int main (void)
{
	char hex;
	int i;
	int a[ARRAY_SIZE];
	int b[ARRAY_SIZE];
	int hamDist = 0;
	FILE* fp;
	
	//Arrays mit 0 initialisieren
	for (i = 0; i < ARRAY_SIZE; ++i)
	{
  		a[i] = 0;
  		b[i] = 0;
	}

	
	fp = fopen("hex.txt","r");
	if (fp == NULL) 
	{
		printf("Die Datei hex.txt wurde nicht gefunden!");
		exit(EXIT_FAILURE);
	}

	i=0;
	printf("1.Zeile einlesen.\n");

 	while((hex=fgetc(fp))!='\n' && hex != EOF)
    {
        a[i]=strtol(&hex,0,16);
		i++;
    }
	i=0;
	printf("2.Zeile einlesen.\n");

 	while((hex=fgetc(fp))!='\n' && hex != EOF)
    {
    	b[i]=strtol(&hex,0,16);
        i++;
    }
	fclose(fp);

	printf("Hamming-Abweichung pro Nibble:\n");
	for (i = 0; i < ARRAY_SIZE; ++i)
	{
		printf ("%i\t%i\t%i\n",a[i],b[i],Hamdist(a[i],b[i]));
		hamDist += Hamdist(a[i],b[i]);
	}
	printf ("\nHamming-Abweichung der Hash-Werte:%d\n",hamDist);
}
stdout
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--- Challenge Reversing Lanjutan ---
Masukkan Serial Key (tepat 21 karakter): 
[FAILURE] Serial Key salah. Coba lagi.
https://ideone.com/VMcFY1
language:
C (gcc 8.3)
created:
9 days ago
visibility:
public

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