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Line 32: − + − The key is generated using the [[AES|AES Engine]] key generator, where the keyX is set by the bootrom (see below for the keyslots) and the keyY is the first 0x10 bytes of the NCCH signature. This method of key generation is referred to as "secure-crypto". + − −
Clarify, restructure.
=== Encryption ===
=== Encryption ===
The extended header, the [[ExeFS]], and the [[RomFS]] are encrypted using 128-bit AES CTR. See here regarding the [https://github.com/3dshax/ctr/blob/master/ctrtool/ncch.c CTR].
The extended header, the [[ExeFS]], and the [[RomFS]] are encrypted using [https://github.com/3dshax/ctr/blob/master/ctrtool/ncch.c 128-bit AES CTR]. The decryption key is generated using the [[AES|AES Engine]] key generator, where the keyX is set by the bootrom (see below for the keyslots). Initially, the keyY was set to the first 0x10 bytes of the NCCH signature ("secure-crypto"). Later firmware updates introduced more sophisticated algorithms.
Starting with [[9.6.0-24|9.6.0-X]] Process9, there is a different method of generating the NCCH keyY which is enabled by setting the bitmask 0x20 in ncchflag[7]: The keyY will be set to a SHA256 hash generated with the data <0x10-long old-method keyY><0x10-long title-unique content lock seed>, where seeds for downloaded titles that use the new crypto are stored in [[Filesystem_services#SEEDDB|SEEDDB]] (nand:/data/<console-unique>/sysdata/0001000f/00000000). When FSUSER OpenFile is used with a NCCH archive where this crypto is used, fs-module will add the seed-data to the end of the [[FSPXI:OpenFile]] file lowpath with the seed from the SEEDDB (this is how Process9 gets the seed data which gets hashed for calculating the NCCH keyY). This new keyY generation is only used for [[RomFS]] and [[ExeFS]] files which don't have filenames "icon" or "banner" (the same sections which would be used for the additional NCCH keyslots, however this keyY generation can be used without any additional NCCH keyslot). This functionality was likely added to support pre-loading of games from the eShop.
Starting with [[9.6.0-24|9.6.0-X]] Process9 can now generate the NCCH keyY with the first 0x10-bytes from a SHA256 hash (when ncchflag[7] has bitmask 0x20 set). This hash is generated with the data <0x10-long old-method keyY><0x10-long title-unique content lock seed>, where seeds for downloaded titles that use the new crypto are stored in [[Filesystem_services#SEEDDB|SEEDDB]] (nand:/data/<console-unique>/sysdata/0001000f/00000000). When FSUSER OpenFile is used with a NCCH archive where this crypto is used, fs-module will add the seed-data to the end of the [[FSPXI:OpenFile]] file lowpath with the seed from the SEEDDB (this is how Process9 gets the seed data which gets hashed for calculating the NCCH keyY). This new keyY generation is only used for [[RomFS]] and [[ExeFS]] files which don't have filenames "icon" or "banner" (the same sections which would be used for the additional NCCH keyslots, however this keyY generation can be used without any additional NCCH keyslot). This functionality was likely added to support pre-loading of games from the eShop.
If a certain NCCH flag is set, a fixed AES key is used. There are two fixed keys, one for titles which have the system category bit set (SystemFixedKey), and one for the rest ("zeros" key). These are debug keys, as they aren't nomally supported on retail systems.
If a certain NCCH flag is set, a fixed AES key is used. There are two fixed keys, one for titles which have the system category bit set (SystemFixedKey), and one for the rest ("zeros" key). These are debug keys, as they aren't nomally supported on retail systems.