Glossary

Terms you will meet across this documentation

A

Apploader: The small program that loads the game into memory and starts it. It lives at a fixed offset in the partition before the file data
Arena: The game’s heap. Everything between arenaLo and arenaHi is available for runtime allocation
arenaLo: The lower bound of the Arena. It is a constant compiled into the boot code, not a value read from anywhere, which is why moving it means patching an instruction. See Code injection

BCSV: A typed table format holding most of a game’s tunable data. Column names are stored as hashes so readable names have to be supplied from outside. See Files, in depth
bi2.bin: A configuration block sitting right after the internal header, holding some parameters. If you have any sourced information of it, i’m taking them
Block: The unit of partition encryption: 0x8000 bytes of which 0x400 are a hash header and 0x7C00 are encrypted data
BNR
opening.bnr: The banner file shown in the Wii menu. An IMET header followed by a U8 archive containing the icon, the banner and the sound
boot.bin: A second disc header. Stored at offset 0 of the decrypted partition data. It carries what the outer header cannot know: the offsets of the DOL and the FST. Extraction tools call it boot.bin. It’s like the header of each partition
bss: Means Block Started by Symbol. It’s not a specific of Nintendo consoles. The memory section of BSS is used for constants and static object. This section is zeroed at load time. Its end is not the start of the Arena: measured across games, arenaLo sits about 0x10000 higher

Certificate chain: The three certificates that would validate a Ticket and a TMD signature on real hardware
CMD
Content metadata: One entry of a TMD, describing a single content: its ID, index, type, size and SHA-1
Code cave: A run of unused bytes inside an existing section, usually nop or zeros large enough to hold a small routine. The cheapest place to put code since it needs no new section
Common key: One of Nintendo’s global AES keys used to decrypt every Title key. Index 0 is the normal key, index 1 the Korean one and index 2 the Wii U in Wii mode

Disc header: The first 0x440 bytes of an ISO unencrypted. Holds the Game ID, the title and the flags that disable encryption or hash verification. See Wii ISO Structure and Decryption Process
DOL: The executable format of Wii games. Up to 7 text and 11 data sections, each declaring the virtual address it must load at. See Working with the DOL
Dolphin: The GameCube and Wii emulator (and also the internal project codename for Gamecube)

Fakesign: Zeroing a signature and brute-forcing a padding field until the SHA-1 of the signed blob starts with a null byte. This exploits a check in the original IOS that compared only the first byte. Also known as Trucha bug
FST
File System Table: The list of files and directories in a partition. It’s stored as a flat array of nodes, not a tree: a directory records the index where its contents end. See Files, in depth

Game ID: Six ASCII characters identifying a release such as RMGE01. The first letter is the console, the next two the game, fourth the region, the last two the publisher. (Might be wrong, i don’t find any source of it)
Group: 64 Block s subdivided into 8 subgroups of 8 blocks. Hashing and encryption operate a group at a time which is why changing one byte costs a whole group

H0
H1
H2
H3: The four levels of the partition hash tree. H0 hashes the 31 subblocks of a block, H1 the 8 blocks of a subgroup, H2 the 8 subgroups of a group and H3 each group. The H3 table lives outside the encrypted data and is itself hashed into the TMD
Hook: Replacing an existing instruction with a branch to your own code, which runs and then returns

IMD5: A small header with an MD5 checksum, wrapping the assets inside a banner
IMET: The header of a BNR, holding the game title in ten languages
IV
Initialization vector: The starting state of an AES-CBC operation. Each encrypted Block stores its own at offset 0x3D0 of its header

Magic word: A sequence of bytes that identifies the file type . 0x5D1C9EA3 at offset 0x18 marks a Wii Disc header for example
MEM1: The 24 MB of main memory mapped from 0x80000000. Game code and most data live here
MEM2: An additional 64 MB mapped from 0x90000000
Merkle tree: A tree in which every non-leaf node is a hash of its children. The Wii partition hash tree is one of it and it is what makes in-place editing impossible. See Rebuilding the disc

Partition: A self-contained individually encrypted section of the disc. DATA holds the game, UPDATE holds a system update, CHANNEL holds virtual channel titles. Wiithon reads and patches DATA for now
Partition table: A table at 0x40000 describing up to four groups of partitions, each entry giving an offset and a type
PowerPC
Broadway: The Wii’s CPU. 32-bit big endian and fixed four-byte instructions. See PowerPC for patching

RARC: Nintendo’s archive format, used to bundle game assets. Frequently wrapped in Yaz0

Ticket: The structure holding the encrypted Title key. One per partition and stored at its very start
Title key: The AES-128 key that encrypts a partition’s data. It is stored encrypted in the Ticket and decrypted with a Common key
TMD
Title metadata: Describes a title and its contents with a SHA-1 hash per content. It also carries the hash of the H3 table, which is why it can only be finalised once the partition is fully encrypted
TPL: Nintendo’s texture format found inside banner archives

Virtual address: The address a section is loaded at as opposed to its offset in the DOL file. All patching APIs in Wiithon take virtual addresses

WiiBrew: The community wiki documenting the Wii’s formats and internals. Most of what Wii ISO Structure and Decryption Process describes was reverse engineered there first
wit: The Wiimms ISO Tools, a command line suite for extracting and rebuilding Wii discs. The directory layout DirectoryPartitionSource expects is the one wit produces