Wii Security

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The Wii has four basic ways of communicating with the environment -- games on DVDs, savegames on SD card, channels/VCs on SD card and updates downloaded from Internet. All of them needs to be protected, for the Wii security model to hold up integrity. Different solutions are in place for all of the ways, even if there are similarities between them.

DVD discs

The DVDs are encrypted to avoid analysis, and signed to avoid modifications.

The encryption is a symmetric crypto, 128 bit AES-CBC. Symmetric means that the same key is used for both encryption and decryption. The Wii DVD contains of several partitions. Each partition has its own AES key. This key is stored on the disc, in the partition information, but it is encrypted with the master AES key. So, with the master AES key you can decrypt the partition keys, and with the partition keys you can decrypt the partitions. Lucky for us, the master AES key was extracted by the Tweezer hack.

The disc is signed by building SHA-1 hashes of small parts of the disc, then aggregating these hashes into a hierarchical structure, which is finally signed with a asymmetric crypto. This solution is chosen for efficiency, since asymmetric cryptos are extremely slow.

For more details, see Partition Data info on the Wiidisc page.

Typically, the first partition contains system updates, in the form of WAD files. The data content of the WAD files themselves are encrypted and signed, as well. It is encrypted by 128 bit AES-CBC, by a title key. The title key is encrypted with the master AES key, and is stored in the WAD.

Savegames on SD cards

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Channels on SD cards

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Internet updates

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