Extdata: Difference between revisions

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=== Encryption ===

These files are ~~encrypted with AES-CTR. The~~ [[AES]] ~~engine keyslot(s) used for extdata crypto and the~~ AES-~~CCM MAC has the console-unique portion of~~ the keyslot~~(s)~~ initialized ~~from~~ [[nand/private/movable.sed|movable.sed]].(The ~~nonce~~ used for the ~~AES-CCM MAC is unknown) Both~~ SD extdata ~~and~~ NAND extdata ~~use the same AES engine keyslot(s)~~. The WCHAR LowPath "/extdata/<ExtdataIDHigh>/<ExtdataIDLow>/<PathToImage>" text path is hashed with SHA-256, including the WCHAR null-terminator. A separate hash is used for Quota.dat. The base CTR seems to be then generated by XORing the calculated hash: CTRword[i] = Hashword[i] ^ Hashword[4+i].

These files are [[AES|encrypted]] with AES-CTR, the keyslot is initialized by [[nand/private/movable.sed|movable.sed]]. The same keyslot is used for the NAND/SD extdata MAC, however NAND extdata is stored in cleartext. The WCHAR LowPath "/extdata/<ExtdataIDHigh>/<ExtdataIDLow>/<PathToImage>" text path is hashed with SHA-256, including the WCHAR null-terminator. A separate hash is used for Quota.dat. The base CTR seems to be then generated by XORing the calculated hash: CTRword[i] = Hashword[i] ^ Hashword[4+i].

The base CTR is fixed therefore 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.

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 === Encryption ===
-These files are encrypted with AES-CTR. The [[AES]] engine keyslot(s) used for extdata crypto and the AES-CCM MAC has the console-unique portion of the keyslot(s) initialized from [[nand/private/movable.sed|movable.sed]].(The nonce used for the AES-CCM MAC is unknown) Both SD extdata and NAND extdata use the same AES engine keyslot(s). The WCHAR LowPath "/extdata/<ExtdataIDHigh>/<ExtdataIDLow>/<PathToImage>" text path is hashed with SHA-256, including the WCHAR null-terminator. A separate hash is used for Quota.dat. The base CTR seems to be then generated by XORing the calculated hash: CTRword[i] = Hashword[i] ^ Hashword[4+i].
+These files are [[AES|encrypted]] with AES-CTR, the keyslot is initialized by [[nand/private/movable.sed|movable.sed]]. The same keyslot is used for the NAND/SD extdata MAC, however NAND extdata is stored in cleartext. The WCHAR LowPath "/extdata/<ExtdataIDHigh>/<ExtdataIDLow>/<PathToImage>" text path is hashed with SHA-256, including the WCHAR null-terminator. A separate hash is used for Quota.dat. The base CTR seems to be then generated by XORing the calculated hash: CTRword[i] = Hashword[i] ^ Hashword[4+i].
 The base CTR is fixed therefore 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.