NCCH: Difference between revisions

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== NCCH Specs ==

The extended header, the [[ExeFS]] and the RomFS are encrypted using 128-bit AES CTR.

The extended header, the [[ExeFS]] and the [[RomFS]] are encrypted using 128-bit AES CTR.

By default encrypted regions are compressed with an LZ77 variant, then encrypted. The spec allows for both unencrypted and uncompressed regions to exist. Retail SD card CXIs must have the [[ExeFS|ExeFS:/.code]] compressed. Development units use a fixed system key for system titles. On retail part of the input [[AES]] engine key is unique per NCCH, the AES engine internally generates the final-normal key.

Retail CFAs use NCCH product code "CTR-P-CTAP", while retail title/gamecard CXIs use NCCH product code "CTR-P-XXXX". This product code is the NCCH [[Serials|serial code]]. ~~<del>This CXI product code is likely used for~~ region-locking.</~~del> There~~ is ~~a value set in~~ the ~~banner used for~~ region~~-locking~~.

Retail CFAs use NCCH product code "CTR-P-CTAP", while retail title/gamecard CXIs use NCCH product code "CTR-P-XXXX". This product code is the NCCH [[Serials|serial code]]. The region-locking info checked by home menu is stored in the [[SMDH#Flags|icon]].

All of the hashes stored in this NCCH header are over the cleartext data. The ExeFS/RomFS superblock starts at offset 0x0 in the ExeFS/RomFS, and the size is specified by the hash region fields.

=== NCCH Header ===

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| 0x160

| 0x20

| Extended header hash~~. SHA256Managed()~~ over ~~first~~ 0x400 ~~bytes of UNENCRYPTED ExHeader.~~

| Extended header SHA-256 hash, over the 0x400-byte exheader

|-

| 0x180

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| 0x1C0

| 0x20

| ExeFS superblock hash~~. SHA256Managed() over first 0x200 bytes of UNENCRYPTED ExeFS.~~

| ExeFS superblock SHA-256 hash

|-

| 0x1E0

| 0x20

| RomFS superblock hash~~. SHA256Managed() over first 0x200 bytes of UNENCRYPTED RomFS.~~

| RomFS superblock SHA-256 hash

|}

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0004ae0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

A tool for parsing this format is available [http://github.com/3dshax/ctr/tree/master/ctrtool here]

A tool for parsing this format is available [http://github.com/3dshax/ctr/tree/master/ctrtool here].

==== Example dependency list from the extended header ====

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=== Extended Header ===

See also: [https://github.com/3dshax/ctr/blob/master/ctrtool/exheader.h]

~~'''NOTE~~: ~~AFTER DECRYPTION'''~~

{| class="wikitable" border="1"

@@ Line 34: / Line 34: @@
 == NCCH Specs ==
-The extended header, the [[ExeFS]] and the RomFS are encrypted using 128-bit AES CTR.
+The extended header, the [[ExeFS]] and the [[RomFS]] are encrypted using 128-bit AES CTR.
 By default encrypted regions are compressed with an LZ77 variant, then encrypted. The spec allows for both unencrypted and uncompressed regions to exist. Retail SD card CXIs must have the [[ExeFS|ExeFS:/.code]] compressed. Development units use a fixed system key for system titles. On retail part of the input [[AES]] engine key is unique per NCCH, the AES engine internally generates the final-normal key.
-Retail CFAs use NCCH product code "CTR-P-CTAP", while retail title/gamecard CXIs use NCCH product code "CTR-P-XXXX". This product code is the NCCH [[Serials|serial code]]. <del>This CXI product code is likely used for region-locking.</del> There is a value set in the banner used for region-locking.
+Retail CFAs use NCCH product code "CTR-P-CTAP", while retail title/gamecard CXIs use NCCH product code "CTR-P-XXXX". This product code is the NCCH [[Serials|serial code]]. The region-locking info checked by home menu is stored in the [[SMDH#Flags|icon]].
+All of the hashes stored in this NCCH header are over the cleartext data. The ExeFS/RomFS superblock starts at offset 0x0 in the ExeFS/RomFS, and the size is specified by the hash region fields.
 === NCCH Header ===
@@ Line 93: / Line 95: @@
 |  0x160
 |  0x20
-|  Extended header hash. SHA256Managed() over first 0x400 bytes of UNENCRYPTED ExHeader.
+|  Extended header SHA-256 hash, over the 0x400-byte exheader
 |-
 |  0x180
@@ Line 153: / Line 155: @@
 |  0x1C0
 |  0x20
-|  ExeFS superblock hash. SHA256Managed() over first 0x200 bytes of UNENCRYPTED ExeFS.
+|  ExeFS superblock SHA-256 hash
 |-
 |  0x1E0
 |  0x20
-|  RomFS superblock hash. SHA256Managed() over first 0x200 bytes of UNENCRYPTED RomFS.
+|  RomFS superblock SHA-256 hash
 |}
@@ Line 231: / Line 233: @@
 ae0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
-A tool for parsing this format is available [http://github.com/3dshax/ctr/tree/master/ctrtool here]
+A tool for parsing this format is available [http://github.com/3dshax/ctr/tree/master/ctrtool here].
 ==== Example dependency list from the extended header ====
@@ Line 258: / Line 260: @@
 === Extended Header ===
+See also: [https://github.com/3dshax/ctr/blob/master/ctrtool/exheader.h]
-'''NOTE: AFTER DECRYPTION'''
 {| class="wikitable" border="1"