The DSiWare exported from a 3DS is located at "sdmc:/Nintendo 3DS/<ID0>/<ID1>/Nintendo DSiWare". Filenames are same format as DSi: "<TitleID-Low>.bin". The below sizes include the 0x20-byte block metadata.
DSiWare exported from 3DS use keyslots initialized by movable.sed. Each section is encrypted with AES-CBC.
The content sections are ordered the same way as DSi: TMD, SRL from content0, <content1-7 for format v2>, savegame, and banner.sav.(ContentX here is the .app data from TWL-NAND /title) The DSiWare export type is specified by AMPXI:ExportDSiWare, this field is also used to specify the format version. For NATIVE_FIRM versions where this DSiWare type field is unused, format version v1 is used. When this field is used, format version v1 is used for DSiWare type value 13, otherwise v2 is used.
Block Metadata
| Offset
|
Size
|
Description
|
| 0x0
|
0x10
|
AES MAC over a SHA-256 hash
|
| 0x10
|
0x10
|
IV, generated by the RNG.
|
Each section begins with the payload encrypted data, followed by this block metadata. The hash used for the MAC is calculated over the the cleartext payload, however it's unknown how this hash is calculated. This hash used for generating the MAC is also stored in the footer.
| Offset
|
Size
|
Description
|
| 0x0
|
X
|
SHA-256 hashes over the banner, header, and content sections.
|
| 0x0 + X
|
0x3C
|
ECDSA signature over the previous data, signed by the AP cert?
|
| 0x3C + X
|
0x180
|
ECDSA "APXXXXXXXXXXXXXXXX" cert signed by the CTCert, where X is random lowercase ASCII hex data.
|
| 0x1BC + X
|
0x180
|
ECDSA CTCert
|
| 0x33C + X
|
0x4
|
Uninitialized padding.
|
These hashes are the same hashes used for generating each section's MAC stored in the metadata block. For format version v1, X is 0xC0. For format version v2, X is at least 0x1A0.
File Structure v1
| Offset
|
Size
|
Description
|
| 0x0
|
0x4020
|
Banner section
|
| 0x4020
|
0xC0
|
Header section
|
| 0x40E0
|
0x340 + X, where X is the total size of the hashes stored in the footer.
|
Footer section
|
| 0x40E0 + footer_size
|
|
Data for the 4 content sections are stored here.
|
| Offset
|
Size
|
Description
|
| 0x0
|
0x4
|
Magic number 0x54444633, "3FDT".
|
| 0x4
|
0x2
|
Byte-swapped groupID from the TWL TMD.
|
| 0x6
|
0x2
|
Byte-swapped title version from the TWL TMD.
|
| 0x8
|
0x20
|
SHA-256 hash calculated over the encrypted movable.sed.
|
| 0x28
|
0x10
|
Encrypted AES block from encrypting an all-zero 0x10-byte block with AES-CBC, where the IV is all-zero.
|
| 0x38
|
0x8
|
Byte-swapped titleID from the TWL TMD.
|
| 0x40
|
0x8
|
?
|
| 0x48
|
0x10
|
u32 payload sizes for the 4 content sections.
|
| 0x58
|
0x4
|
?
|
| 0x5C
|
0x3E
|
Data from the TWL TMD reserved section. Only the first 0x20-bytes from the TWL TMD is written here, the rest is uninitialized.
|
| 0x9A
|
0x6
|
Padding?
|
File Structure v2
| Offset
|
Size
|
Description
|
| 0x0
|
0x4020
|
Banner section
|
| 0x4020
|
0x110
|
Header section
|
| 0x4130
|
0x340 + X, where X is the total size of the hashes stored in the footer.
|
Footer section
|
| 0x4130 + footer_size
|
|
Data for the 11 content sections are stored here.
|
| Offset
|
Size
|
Description
|
| 0x0
|
0x4
|
Magic number 0x54444633, "3FDT".
|
| 0x4
|
0x2
|
Byte-swapped groupID from the TWL TMD.
|
| 0x6
|
0x2
|
Byte-swapped title version from the TWL TMD.
|
| 0x8
|
0x20
|
SHA-256 hash calculated over the encrypted movable.sed.
|
| 0x28
|
0x10
|
Encrypted AES block from encrypting an all-zero 0x10-byte block with AES-CBC, where the IV is all-zero.
|
| 0x38
|
0x8
|
Byte-swapped titleID from the TWL TMD.
|
| 0x40
|
0x8
|
?
|
| 0x48
|
0x2C
|
u32 payload sizes for the 11 content sections.
|
| 0x74
|
0x30
|
?
|
| 0xA4
|
0x3E
|
Data from the TWL TMD reserved section. Only the first 0x20-bytes from the TWL TMD is written here, the rest is uninitialized.
|
| 0xE2
|
0x0E
|
Padding?
|