[rikhal]

Recently I was informed that Datel has released a new version of their Action Replay Cheat Cartridge that allows you to cheat in DS games on a DSi console. Knowing that Nintendo put quite some effort in blocking any third party cartridges from working on the DSi I was curious to figure out how they did it.

Before jumping in this article, I’ll give you a small warning that what is written here might be quite “techy” to some people, I advise reading lots of GBAtek (And maybe a bit of dsibrew) when you get lost.

Research™ has shown that getting a DS cart to boot on a DSi requires quite a bit more effort then it did on a (DS)Lite. Cart timings are very important, you cannot eject the cartridge and insert a new one beyond the DSi menu. But most important of all, the DSi menu does additional integrity checking prior to booting the cartridge.

The integrity checking is there to ensure that the cartridge booted is a genuine licensed game cartridge. There is a whitelist stored in the DSi’s NAND, that has an entry for every DS game released, consisting of multiple SHA1 (How these hashes are constructed exactly hasn’t been confirmed) checksums for the cart header, ARM9 binary and ARM7 binary.