Why does the `strcpy` function cause problems when delivering shellcode, and what solution is applied in the article?

The `strcpy` function stops copying when it encounters a null byte (0x00), so if the shellcode contains null bytes, only part of it is copied into the buffer, preventing proper exploitation. To avoid this, the author XOR-encrypts the shellcode byte‑by‑byte (e.g., with 0x44) and prepends a small decoder that decrypts the shellcode at runtime, stopping when it hits a 0x90 byte. This technique is a common shellcode optimization to bypass null‑byte restrictions.