NCSD
This page documents the format of NCSD.
Overview
There are two known specialisations of the NCSD container format. The CTR Cart Image (CCI) format and the CTR System Update (CSU). CCI is the format of retail game ROM dumps. CSU is used with developer system updates and tools
NCSD images start with a NCSD header, followed by up to a maximum of 8 NCCH partitions. The first partition(NCCH 0) usually starts at 0x4000, this is generally the main NCCH (Executable). The following info on partitions 1, 2, and 7 are only valid for .CCI. The second partition(NCCH 1) contains the game's Electronic Manual(The partitionID-high for the Instruction Manual .CFA is always 0x00050000). The third partition(NCCH 2) contains the download play "Child"(The partitionID-high for the .CFA containing the DLP Child is always 0x00060000). The eighth block(NCCH 7) contains "Update Data"(The partitionID-high for the .CFA containing the Update Data is always 0x80000000). The format of partitions can be determined from the partition FS flags, while the contents can be determined from the partitions flags.
NCSD header
| Offset | Size | Description |
|---|---|---|
| 0x000 | 0x100 | RSA-2048 SHA-256 signature of the NCSD header |
| 0x100 | 4 | Magic Number 'NCSD' |
| 0x104 | 4 | Size of the NCSD image, in media units (1 media unit = 0x200 bytes) |
| 0x108 | 8 | Media ID |
| 0x110 | 8 | Partitions FS type |
| 0x118 | 8 | Partitions crypt type |
| 0x120 | 0x40=(4+4)*8 | Offset & Length partition table |
| 0x160 | 0x20 | Exheader SHA-256 hash |
| 0x180 | 0x4 | Additional header size |
| 0x184 | 0x4 | Sector zero offset |
| 0x188 | 8 | Partition Flags (See Below) |
| 0x190 | 0x40=8*8 | Partition ID table |
| 0x1D0 | 0x30 | Reserved |
Partition Flags
| Byte Index | Description |
|---|---|
| 3 | Media Card Device (1 = NOR Flash, 2 = None, 3 = BT) |
| 4 | Media Platform Index (1 = CTR) |
| 5 | Media Type Index (0 = Inner Device, 1 = Card1, 2 = Card2, 3 = Extended Device) |
| 6 | Media Unit Size i.e. u32 MediaUnitSize = 0x200*2^flags[6]; |
| 7 | Media Card Device (Used Prior to SDK 3.X) |
Partition Flags (In Terms of Save Crypto Determination)
| Byte Index | Description |
|---|---|
| 0 | Unknown, NATIVE_FIRM loads this flag from the gamecard NCSD header starting with 6.0.0-11. |
| 1 | Starting with 6.0.0-11 NATIVE_FIRM will use this flag to determine the gamecard savegame keyY method, when flag[3] is set. 2 = hashed keyY, 3 = new keyY method implemented with 6.0.0-11. |
| 3 | Support for this flag was implemented in NATIVE_FIRM with 2.0.0-2. When this flag is set the hashed gamecard savegame keyY method is used, this likely still uses the repeating-CTR however. With 6.0.0-11 the system will determine the gamecard savegame keyY method via flag[1], instead of just using the hashed keyY via this flag |
| 7 | This flag enables using the hashed gamecard savegame keyY method, support for this flag was implemented in NATIVE_FIRM with 2.2.0-4. All games with the NCSD image finalized since 2.2.0-4(and contains 2.2.0-4+ in the system update partition) have this flag set, this flag also enables using new CTR method as well. |
Card Info Header
| OFFSET | SIZE | DESCRIPTION |
|---|---|---|
| 0x200 | 4 | Writable Address In Media Units (For 'On-Chip' Savedata) |
| 0x200 | 4 | Card Info Bitmask |
| 0x208 | 0xDF8 | Reserved1 |
| 0x1000 | 8 | Media ID (same as first NCCH partitionId) |
| 0x1008 | 8 | Reserved2 |
| 0x1010 | 0x30 | Initial Data |
| 0x1040 | 0xC0 | Reserved |
| 0x1100 | 0x100 | Copy of first NCCH header (excluding RSA signature) |
Development Card Info Header Extension
| OFFSET | SIZE | DESCRIPTION |
|---|---|---|
| 0x1200 | 0x200 | CardDeviceReserved1 |
| 0x1400 | 0x10 | TitleKey |
| 0x1410 | 0xF0 | CardDeviceReserved2 |
Tools
ctrtool - (CMD)(Windows/Linux) Parsing NCSD files
3DSExplorer - (GUI)(Windows Only) Parsing NCSD files