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: byte[5]-byte[7] indicate content type ( system update, application, manual, ... ) size of media units ( 512*2^byte[6] ) and encryption.
0x190	0x40=8*8	Partition ID table
0x1D0	0x30	Reserved

Partition Flags

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	8	Card Info
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