1. Encrypt all strings
2. Obfuscate all function calls
3. Change XOR to AES

Real life applications

1.  Think about how you could hide your encrypted payload behind an image. Hint: file concatenation. Implement a new dropper.
2.  Build a dropper, which hosts its payload in a separate AES-encrypted file (on disk or on a file share). Hint: use CreateFile() and ReadFile(); example code.