/*
	JPEG Image Decryption B1
	
	Input: dataen.bin
	Output: out.jpg
*/

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

#define WAIT system("PAUSE")
#define BUFFLENGTH 30000

int main(int argc, char *argv[])
{
  unsigned char input[BUFFLENGTH];
  unsigned char key[] = "MEETMEATTOGARPARTY";
  int count=0;
  FILE* file;

  //Read file
  if( (file = fopen("dataen.bin", "rb")) != NULL)
  {
		count = fread(input, 1, BUFFLENGTH, file);
		input[count] = '\0';
		printf("Read: %d\n", count);
		fclose(file);
  }
  else{
		printf("Error reading file!!!\n");
		goto EXIT;
  }
  
  //Enter the encryption process
  int i;
  for(i=0; i<count; i++)
  {
		//#1 Encryption State 2: Exchange the byte-value
		if(input[i] == 28)
			input[i] = 128;
		else if(input[i] == 96)
			input[i] = 52;
		else if(input[i] == 51)
			input[i] = 72;
		else if(input[i] == 9)
			input[i] = 1;
		else if(input[i] == 102)
			input[i] = 22;
		else if(input[i] == 91)
			input[i] = 90;
			
		//#2 Encryptiong State 1: XOR each byte with key[]
		input[i] = input[i] ^ key[i % (sizeof(key)-1)];
  }
  
  //Write to output
  //Read file
  if( (file = fopen("out.jpg", "wb")) != NULL)
  {
		count = fwrite(input, 1, count, file);
		printf("Write: %d\n", count);
		fclose(file);
  }
  else{
		printf("Error reading file for writing!!!\n");
		goto EXIT;
  }
  
  printf("Completed!!!\n");
EXIT:
  WAIT;
  return 0;
}