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This page describes the format and encryption of extdata, "extra data" stored on [[SD_Filesystem|SD card]] and NAND.

This page describes the format and encryption of extdata, "extra data" stored on [[SD_Filesystem|SD card]] and NAND.

At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/<ExtdataIDHigh> on SD is directories for each title.(ExtdataIDHigh seems to be always 00000000) Some titles have Quota.dat stored in these directories, not all titles use it. The dirname for these directories is the ExtdataIDLow. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.

At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/<ExtdataIDHigh> on SD is directories for each title.(ExtdataIDHigh is always 00000000) Some titles have Quota.dat stored in these directories, not all titles use it. The dirname for these directories is the ExtdataIDLow. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.

Regular apps can only mount SD/NAND extdata using the same extdataID which is stored in the [[CXI]] exheader. Therefore, regular apps which have the exheader extdataID set to zero can't use extdata. This restriction doesn't apply for NAND extdataIDs with bitmask 0x48000 set. System apps can mount arbitrary extdata.

Regular apps can only mount SD/NAND extdata using the same extdataID which is stored in the [[CXI]] exheader. Therefore, regular apps which have the exheader extdataID set to zero can't use extdata. This restriction doesn't apply for shared extdata with extdataID high bitmask 0x48000 stored on NAND. System apps can mount arbitrary extdata.

All NAND extdata is shared extdata, while all SD extdata is normal extdata. Thus, normal extdata doesn't exist on NAND, and shared extdata doesn't exist on SD. The extdataID high excluding that bitmask is always zero for shared extdata.

=== Encryption ===

=== Encryption ===