extra5.c xor encrypt

  1 #include <stdio.h>
  2 #include <string.h>
  3 #include <stdlib.h>
  4
  5 int encrypt_data(FILE *);
  6
  7 int main(void)
  8 {
  9         FILE *file_ptr;
 10         int return_code;
 11         char file_name[50];
 12
 13         printf("What would you like to name your file to be encrypted?\n");
 14         scanf("%s", &file_name);
 15
 16         file_ptr = fopen(file_name, "r+");
 17
 18         if(file_ptr == NULL)
 19                 printf("File does not exist.\n");
 20         else
 21                 printf("File exists.\n");
 22
 23
 24
 25         return_code = encrypt_data(file_ptr);
 26         fclose(file_ptr);
 27         printf("\n");
 28         return 0;
 29 }
 30
 31 int encrypt_data(FILE *disk_file_ptr)
 32 {
 33         int i;
 34         unsigned long int file_size;
 35         int key_length;
 36         char *file_buffer = NULL;
 37
 38         char key[] = "ABCDEF";
 39
 40         key_length = strlen(key);
 41
 42         fseek(disk_file_ptr, 0, SEEK_END);
 43         file_size = ftell(disk_file_ptr);
 44
 45         rewind(disk_file_ptr);
 46
 47         file_buffer = malloc(file_size);
 48
 49         if(fread(file_buffer, file_size, 1, disk_file_ptr) != 1)
 50         {
 51                 printf("Error in reading file\n");
 52                 return -1;
 53         }
 54
 55         for(i=0; i<file_size; i++)
 56         {
 57                 file_buffer[i] = file_buffer[i]^key[i%key_length];
 58         }
 59
 60         rewind(disk_file_ptr);
 61
 62         if(fwrite(file_buffer, file_size, 1, disk_file_ptr) != 1)
 63         {
 64                 printf("Error in writing encrypted data to file\n");
 65                 return -1;
 66         }
 67
 68         free(file_buffer);
 69
 70         return 0;
 71 }
 72