I guess I had posted an older version of the .h file. Here's a new one.

Code:
#include <fstream.h>

void encrypt(char *filein, char *fileout, long key, long key2); //encryption routine
void decrypt(char *filein, char *fileout, long key, long key2); //decryption routine
char ch;

void encrypt(char *filein, char *fileout, long key, long key2)
{
    ifstream in(filein, ios::binary);
    ofstream out(fileout, ios::trunc | ios::binary);

    srand(key);
    key = rand() % key2 + 3;
    srand(key2);
    key2 = rand();

    while(!in.eof())
    {
        in.get(ch);
        ch += key;
        ch += key2 % key;
        out.put(ch);
    }
    
    in.close();
    out.close();
    exit(0);
}

void decrypt(char *filein, char *fileout, long key, long key2)
{
    ifstream in(filein, ios::binary);
    ofstream out(fileout, ios::trunc | ios::binary);

    srand(key);
    key = rand() % key2 + 3;
    srand(key2);
    key2 = rand();
    
    while(!in.eof())
    {
        in.get(ch);
        ch -= key2 % key;
        ch -= key;
        out.put(ch);
    }
    in.close();
    out.close();
    exit(0);
}
This algorithm successfully encrypted, and decrypted a file called netscan.exe. That attachment here will contain the source. A CPP which is a UI, and an H, which is the algorithm above. Also is a compiled version, with Dev-C++. I'll have another post containing the netscan and it's encrypted version. I changed the extension of Archive.exe to a .ZIP so I could attach it here. Rename the file to Archive.exe, and extract everything.