MOGG File Format

MOGG files are often used in Harmonix games for all platforms except for PS2 and DS. They are an extension of the OGG Vorbis container with an extra header prepending it, and almost all official MOGGs starting with Rock Band shipped on-disk and as DLC are encrypted.

The version value in the MOGG header is used to indicate which encryption key and format should be used for decryption.

Structure

MOGG Header

Name	Type	Size	Function
Version	Integer (LE)	4 bytes	Version of the MOGG file. Related to encryption (10 / 0xA = unencrypted)
Header Size	Integer (LE)	4 bytes	Length of the MOGG header / offset in the file where the OGG begins.
Map Version	Integer (LE)	4 bytes	Version of the MOGG map. (usually 16 / 0x10)
Seek Interval	Integer (LE)	4 bytes	The interval between samples in the sample table. (Usually 20000 / 0x4E20)
Entry Count	Integer (LE)	4 bytes	The number of entries in the MOGG header.
Sample Table	#MOGG Sample Entry Array	sizeof(MOGG Entry) * Entry Count	A lookup table to help the game stream the OGG file from disk.
AES Key	Byte Array	16 bytes	An AES key used to encrypt the file. Only present if MOGG version is >= 11 / 0xB.

MOGG Sample Entry

To help the game seek in an OGG file (rewinding after pausing, practice mode, etc), a lookup table is used to locate the byte offset in the file to look for a sample.

When the game wants to seek to sample N, it looks up entry (N / Seek Interval) in the table, that gives a byte offset and sample offset. It then seeks the file over to the byte offset and skips (N - Sample Offset) samples.

Name	Type	Size	Function
Byte Offset	Integer (LE)	4 bytes	Offset into the file that the entry starts.
Sample	Integer (LE)	4 bytes	The sample in the OGG stream that corresponds to the byte offset.

OGG File

Past this point is a regular (optionally encrypted) OGG Vorbis format file containing multiple tracks. The tracks corresponding to instruments are defined in the songs.dta file.

Encryption

At its core, files are encrypted with a 128-bit AES EBC cipher. Each "generation" of MOGG files changes the encryption keys and scheme used. For legal reasons this wiki can not document any keys themselves, or any explicit details about 0x11 encryption.

Generation	Info	Games
10 / 0xA	Unencrypted. Lacks key in MOGG header.	Used in Guitar Hero 2 (Xbox 360)
11 / 0xB	Encryption is done with a static key. Uses key in MOGG header as IV.	Used in Rock Band on-disc and DLC songs.
12 / 0xC	The true decryption key is derived through a custom algorithm. Changes the format of the header.	Used in Rock Band 2 on-disc songs.
14 / 0xE	Increases the complexity of the key derivation step.	Used in Rock Band 2 DLC songs.
15 / 0xF
16 / 0x10		Used in Rock Band 3, Rock Band 4 and Rock Band VR on-disc and DLC until November 2018.
17 / 0x11	A new value is added in the header and a new set of keys are used for a more complex key derivation step.	Used in Rock Band 4 DLC after November 2018, as well as Fuser.

Keys in Rock Band 2 (Xbox 360) and later are additionally protected behind the console's native XeKeys functions (XeKeysAesCbc). This was likely to prevent those with development kits from reverse engineering the new algorithm, as XeKeys uses different keys depending on the console's key vault.

TODO: is 13/0xD ever used? Validate if the games and descriptions are correct.

The Beatles: Rock Band used version 16/0x10 behind a Cloakware's white-box crypto algorithm in order to protect the original keyset.

Tools

Several tools are available for working with MOGG files (creation/extraction, encryption, etc)

• Onyx Music Game Toolkit
• Magma
• ArkTool
• C3 CON Tools
• Audacity (supports reading smaller unencrypted MOGG files if the header is small)

References

• xorloser's ScoreHero post
• Onyx Toolkit Source Code
• ogg2mogg Source Code
• "Breaking Beatles" - maxton - Archived on 4th December 2020