Extdata: Difference between revisions

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At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/00000000 is directories for each title, with Quota.dat inside each dir. Quota.dat doesn't exist for all titles. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.

These files are encrypted with AES-CTR. The key is unknown, this is console-unique. The CTR includes the titleID and filename. The base CTR is fixed: the CTR never changes after each write. Thus it is possible to obtain some cleartext by XORing one file(like newly created extdata) with a newer file, where the newer file overwrote zeros in the original file with non-zero data. Most extdata uses the same FS as [[savegames]], except extdata uses DIFF instead of DISA. However some extdata files are raw, without any FS.

=== Encryption ===

These files are encrypted with AES-CTR. The key is unknown, this is console-unique. The CTR includes the titleID and filename. The base CTR is fixed: the CTR never changes after each write. Thus it is possible to obtain some cleartext by XORing one file(like newly created extdata) with a newer file, where the newer file overwrote zeros in the original file with non-zero data.

=== Filesystem ===

Most extdata uses the same FS as [[savegames]], except extdata uses [[Savegames|DIFF]] instead of DISA. However some extdata files are raw, without any FS.

Quota.dat seems to use the same FS and encryption as the actual extdata?

'''QUOT'''

* This seems to be stored in the Quota.dat FS image somewhere?

{| class="wikitable"

|-

! Start

! Length

! Description

|-

| 0x0

| 4

| Magic ("QUOT")

|-

| 0x4

| 4

| Magic Number? (0x30000)

|-

| 0x8

| 8

| Unknown

|-

| 0x10

| 0x38

| Unknown

|}

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 At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/00000000 is directories for each title, with Quota.dat inside each dir. Quota.dat doesn't exist for all titles. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.
-These files are encrypted with AES-CTR. The key is unknown, this is console-unique. The CTR includes the titleID and filename. The base CTR is fixed: the CTR never changes after each write. Thus it is possible to obtain some cleartext by XORing one file(like newly created extdata) with a newer file, where the newer file overwrote zeros in the original file with non-zero data. Most extdata uses the same FS as [[savegames]], except extdata uses DIFF instead of DISA. However some extdata files are raw, without any FS.
+=== Encryption ===
+These files are encrypted with AES-CTR. The key is unknown, this is console-unique. The CTR includes the titleID and filename. The base CTR is fixed: the CTR never changes after each write. Thus it is possible to obtain some cleartext by XORing one file(like newly created extdata) with a newer file, where the newer file overwrote zeros in the original file with non-zero data.
+=== Filesystem ===
+Most extdata uses the same FS as [[savegames]], except extdata uses [[Savegames|DIFF]] instead of DISA. However some extdata files are raw, without any FS.
+Quota.dat seems to use the same FS and encryption as the actual extdata?
+'''QUOT'''
+* This seems to be stored in the Quota.dat FS image somewhere?
+{| class="wikitable"
+|-
+! Start
+! Length
+! Description
+|-
+| 0x0
+| 4
+| Magic ("QUOT")
+|-
+| 0x4
+| 4
+| Magic Number? (0x30000)
+|-
+| 0x8
+| 8
+| Unknown
+|-
+| 0x10
+| 0x38
+| Unknown
+|}