This is the format on the files stored on SD, unknown if this is used elsewhere.
The data between this header and offset 0x4000 is unused/uninitialized it appears. The actual content which is encrypted, starts at offset 0x4000 with the size from the header.
When a NAX0 file is recreated, the header and raw content in NAX0 are completely different except for the magicnum and size-field. This is the case when a title is redownloaded/reinstalled, and when "save/" files are recreated after manual deletion.
Error 0x250E02 is returned by NCM when attempting to access a NcaId where the NAX0 header was manually modified, for example: offset 0x0, 0x10, 0x28, 0x38, each with size 0x1.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x20 | Data appears to be random. |
| 0x20 | 0x8 | Magicnum "NAX0" |
| 0x28 | 0x20 | Data appears to be random. |
| 0x48 | 0x8? | Size of the file relative to offset 0x4000. |