Question

I am creating a very basic encryption program using XOR to encrypt a user file and decrypt it again. What’s happening however is when I encrypt I get a long line of the same 6 letters and when I try to decrypt it doesn’t work. Can anyone spot the problem? Also, I will want to replace the XOR with a basic encryption method of my own but retain the same code except for the key. Will this be possible? Thanks!

#include <stdio.h>

int main(int argc, char*argv[])
{
FILE *fp1, *fp2;
char* key;
int c;

key = argv[1];

    if(*key != '\0')
    {
    fp1 = fopen(argv[2],"rb");
        if(fp1 != NULL)
        {
            fp2 = fopen(argv[3],"wb");
            if (fp2 != NULL)
            {
            while((c=getc(fp1)!=EOF))
            {
                if(!*key)key = argv[1];
                c ^=*(key++);

                putc(c, fp2);
            }
            fclose(fp2);
            }
        fclose(fp1);
        }
    }
return 1;
}

Answer 1

Check your parenthesis: the while should be

while((c=getc(fp1))!=EOF)