Cart crypto demo
================

This tool decrypts the 3DS cart encryption example on [3dbrew](https://3dbrew.org/wiki/Gamecards).

The code is based on code found on [GBATEK](https://problemkaputt.de/gbatek.htm#3dscartridgeregisters) (**Warning:** big page).

It expects a file named `0004000000038c00.3ds` in the current directory. A known-good dump of this title (LEGO Star Wars III The Clone Wars, EUR) has SHA-256 8fcbd4b394f765cb09f81ee7c62802d490c86ed85bd5ab3923b48a4d0222de22.

It assumes gamecart ID2 == 0, which should be the case for all retail carts.

Secrets
-------

To use this, you need a file called `ctr_secrets.py` in the directory where `cart.py` is. It needs to define a few things:

It needs to define `KEY_DERIVATION_CONSTANT` as an integer (`0x1##############################a`).

It needs to define `CART_KEYS` as an array or tuple like this:

    CART_KEYS = ( # indexed based on ID2
        {
            'rc4': 0x4##############################7,
            'snow': 0xd##############################4
        },
        {
            'rc4': 0x3##############################9,
            'snow': 0xd##############################4
        },
        {
            'rc4': 0x0##############################0,
            'snow': 0x0##############################0
        },
        {
            'rc4': 0x7##############################c,
            'snow': 0x0##############################a
        }
        )

Note that these are *integers*.

It needs to define an array or tuple `BOOTROM_KEYS` like this:

    BOOTROM_KEYS = (
            { # AES slot 0x00
                'keyX': b'',
                'keyY': b'',
                'normalkey': b'',
            },
            { # AES slot 0x01
                'keyX': b'',
                'keyY': b'',
                'normalkey': b'',
            },
            # etc.
            ) * 0x40

Note that these are *bytes*. You can use [yellows8's boot9 tools](https://github.com/yellows8/boot9_tools) to extract the required keyX for slot 0x3b.