Шифрование данных

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SIZE 18
 
int key;
 
void crypt(char *s, char *t)
{
    while ( *s != '\0')
    {
        *t=*s^key;
        s++;
        t++;
    };
}
main()
{
    srand(time(0));
    key = rand()%254+1;
    char str1[SIZE]="It is test string";
    char str2[SIZE]="";
    char str3[SIZE]="";
    int i;
    crypt(str1,str2);
    crypt(str2,str3);
    printf("%d\n%s\n%s\n%s\n",key,str1,str2,str3);
}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
void genKeyFile(char *fileName)
{
    srand(time(0));
    char key = rand()%254+1;
    FILE *fkey = fopen(fileName, "w");
    fputc(key,fkey);
    fclose(fkey);
}
void cryptFile(char *srcFile, char *dstFile, char *keyFile)
{
    FILE *fkey = fopen(keyFile, "r");
    char key = fgetc(fkey);
    fclose(fkey);
 
    FILE *src = fopen(srcFile, "r");
    FILE *dst = fopen(dstFile, "w");
 
    char ch;
    
    while((ch = fgetc(src))!=EOF)
        fputc(ch^key, dst);
 
    fclose(src);
    fclose(dst);
}
main()
{
    char *srcfn = "in.txt";
    char *dstfne = "out_enc.txt";
    char *dstfnd = "out_dec.txt";
    char *keyfn = "key,dat";
 
    genKeyFile(keyfn);
    cryptFile(srcfn,dstfne,keyfn);
    cryptFile(dstfne,dstfnd,keyfn);
    
}