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This document is about the format of CTR cart images (CCI), which is also the format of 3DS ROM dumps.


CCI files start with a NCSD header, followed by 3 NCCH blocks. The first block usually starts at 0x4000. While it is unknown what each NCCH block is for, the first one is most likely the main program code since it is much bigger than the others.

The NCCH blocks are in the same format as CXI files.

NCSD header

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.