Thread: Xor Algorith (need help !)

Hello, it's my first time posting on this forum, i need help w/ my xor algorithm :
So basicly my whole program works, if this one condition is valid (and i don't understand why)
If my message (taken from a file) is in caps lock, my key (inputed "gets")should not be in caps lock and vice versa.

Here is my code, and any idea is welcomed !

Code:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#defineMAX_BUFFER_SIZE10000
typedef unsigned char byte;

//strncat(key, key, strlen(phrase) - strlen(key));

void repeat_key(byte * phrase, byte * key)
{
  byte new[MAX_BUFFER_SIZE];
  int i;
  int cmpt = 0;

  for (i = 0; i < strlen(phrase); i++) {
    if (cmpt == strlen(key))
      cmpt = 0;
    new = key[cmpt];
    cmpt++;
  }
  new = '\0';
  strcpy(key, new);
}

void cut_key(byte * phrase, byte * key)
{
  byte new[MAX_BUFFER_SIZE];
  int i;
  for (i = 0; i < strlen(phrase); i++) {
    new = key;
  }
  new = '\0';
  strcpy(key, new);
}

void xorCipher(byte * key, FILE * file_src_P, FILE * file_dest_P)
{
  byte msg[MAX_BUFFER_SIZE];
  char output[MAX_BUFFER_SIZE];
  int i;

  fgets(msg, MAX_BUFFER_SIZE, file_src_P);

  if (strlen(key) > strlen(msg)) {
    cut_key(msg, key);
    for (i = 0; i < strlen(msg); i++) {
      output = msg ^ key;
    }
    output = '\0';
    if (fprintf(file_dest_P, "%s", output) < 0) {
      printf("Erreur fprintf !\n");
      exit(1);
    };
  } else if (strlen(key) < strlen(msg)) {
    repeat_key(msg, key);
    for (i = 0; i < strlen(msg); i++) {
      output = msg ^ key;
    }
    output = '\0';
    if (fprintf(file_dest_P, "%s", output) < 0) {
      printf("Erreur fprintf !\n");
      exit(1);
    };
  } else if (strlen(key) == strlen(msg)) {
    for (i = 0; i < strlen(msg); i++) {
      output = msg ^ key;
    }
    output = '\0';
    if (fprintf(file_dest_P, "%s", output) < 0) {
      printf("Erreur fprintf !\n");
      exit(1);
    };
  }
}

int main()
{
  byte key[MAX_BUFFER_SIZE];
  FILE *f_s_p = fopen("source.txt", "r");
  FILE *f_d_p = fopen("destination.txt", "w");
  //FILE * f_s_p = fopen("destination.txt","r");
  //FILE * f_d_p = fopen("source.txt","w");

  printf("Entrez clef : ");
  gets(key);

  if (strlen(key) == 0) {
    printf("Entrez une clef valide !\n");
    exit(1);
  }

  if (f_s_p == NULL || f_d_p == NULL) {
    printf("Erreur fopen !\n");
    exit(1);
  }

  xorCipher(key, f_s_p, f_d_p);

  fclose(f_s_p);
  fclose(f_d_p);

  return 0;

}

> So basicly my whole program works, if this one condition is valid (and i don't understand why)
Surely not.....

Code:

foo.c:18:9: error: assignment to expression with array type
     new = key[cmpt];
         ^
foo.c:21:7: error: assignment to expression with array type
   new = '\0';
       ^

And a whole raft of warnings.