Changes

=== Encryption ===

=== Encryption ===

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] unless the NoCrypto mask is set in ncchflag[7]. There are different sets of encryption parameters in use, as over the time new system updates introduced more sophisticated means of encryption. Generally, the decryption key is generated using the [[AES|AES Engine]] key generator by selecting a particular key slot (see below), the keyX of which is usually set by the bootrom and keyY of which was originally set to the first 0x10 bytes of the NCCH signature.

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] unless the NoCrypto flag is set in ncchflag[7]. There are different sets of encryption parameters in use, as over the time new system updates introduced more sophisticated means of encryption. Generally, the decryption key is generated using the [[AES|AES Engine]] key generator by selecting a particular key slot (see below), the keyX of which is usually set by the bootrom and keyY of which was originally set to the first 0x10 bytes of the NCCH signature.

'''NOTE: For a full understanding of the steps involved in decryption, consult the [https://github.com/Relys/Project_CTR ctrtool] and [https://github.com/archshift/Decrypt9 Decrypt9] source code instead.'''.

'''NOTE: For a full understanding of the steps involved in decryption, consult the [https://github.com/Relys/Project_CTR ctrtool] and [https://github.com/archshift/Decrypt9 Decrypt9] source code instead.'''.

As of [[7.0.0-13|7.0.0-X]] the system supports a new encryption method for secure-crypto (when ncchflag[3] != 0). Where a second key is generated using the same keyY but with another [[AES|keyslot]]. The second key is used to crypt the [[RomFS]] and [[ExeFS]] files which don't have filenames "icon" or "banner" (i.e. ".code" and ".firm"). While everything else is crypted with the original key. Note the CTR used is the same for both keys. This makes titles "recognizable" but not "launchable" on systems which don't support this method or the keyslot used.

As of [[7.0.0-13|7.0.0-X]] the system supports a new encryption method for secure-crypto (when ncchflag[3] != 0). Where a second key is generated using the same keyY but with another [[AES|keyslot]]. The second key is used to crypt the [[RomFS]] and [[ExeFS]] files which don't have filenames "icon" or "banner" (i.e. ".code" and ".firm"). While everything else is crypted with the original key. Note the CTR used is the same for both keys. This makes titles "recognizable" but not "launchable" on systems which don't support this method or the keyslot used.

See below for the keyslots used for the additional NCCH keyslots. On Old3DS, as of [[9.6.0-24|9.6.0-X]], Process9 will *only* use keyslot 0x25 when ncchflag[3] is non-zero.

See below for the keyslots used in NCCH crypto. As of [[9.6.0-24|9.6.0-X]], Old3DS Process9 will *only* use keyslot 0x25 when ncchflag[3] is non-zero.

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

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

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!  FW Introduced

!  FW Introduced

!  Old3DS

!  Old3DS

!  AES Keyslot

!  [[AES#Keyslot|AES Keyslots]]

!  Notes

!  Notes

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|  0x01

|  0x01