This document is about the format of CTR cart images (CCI), which is also the format of 3DS ROM dumps.
Overview
CCI files start with a NCSD header, followed by 3 NCCH blocks. The first block usually starts at 0x4000. The first block contains the main game code/data, the second block contains the download play code/data and the third block contains potential system updates.
The NCCH blocks are in the same format as CXI files.
NCSD header
| OFFSET | SIZE | DESCRIPTION |
|---|---|---|
| 0x000 | 0x100 | RSA-2048 signature of the NCSD header, using SHA-256 (needs to be confirmed) |
| 0x100 | 4 | Magic ID, always 'NCSD' |
| 0x104 | 4 | Size of the CCI image, in media units (1 media unit = 0x200 bytes) |
| 0x108 | 8 | Title/Program ID |
| 0x120 | 4 | Offset to the first NCCH in media units |
| 0x124 | 4 | Size of the first NCCH |
| 0x130 | 4 | Offset to the second NCCH |
| 0x134 | 4 | Size of the second NCCH |
| 0x158 | 4 | Offset to the third NCCH |
| 0x15C | 4 | Size of the third NCCH |
| 0x188 | 8 | NCCH Flags: byte[5]-byte[7] indicate content type ( system update, application, ... ) size of media units ( 512*2^byte[6] ) and encryption. |
| 0x190 | 8 | Partition ID of the first NCCH |
| 0x1A0 | 8 | Partition ID of the second NCCH |
| 0x1C8 | 8 | Partition ID of the third NCCH |
| 0x200 | 4 | Always 0xFFFFFFFF |
| 0x300 | 4 | Used ROM size in bytes |
| 0x320 | 16 | Unknown |
Parts of the first NCCH block's header are found around 0x1000 for whatever reason.
CCI images may not include all three NCCH blocks. For example, Ghost Recon: Shadow Wars lacks the second NCCH. Entries at 0x130, 0x134 and 0x1A0 in its NCSD header are zero.