CIA stands for CTR Importable Archieve. These files contain a compiled application which can be installed on CTR NAND, TWL NAND (part of the NAND used by DSi applications) and on the SD card. CIA files can be created with the Nintendo 3DS SDK and installed on the 3DS test units by the Dev channel.
The CIA format based on WAD format, so the structure is very similar to the WAD structure. The file is represented in little-endian.
|0x00||0x03||0x04||constant header size = 0x2020 bytes|
|0x04||0x07||0x04||Reserved = 0|
|0x08||0x0B||0x04||Certificate chain size|
|0x10||0x13||0x04||TMD file size|
|0x14||0x17||0x04||Banner size (0 if no banner)|
|0x18||0x18||0x01||0 (reserved, flag?)|
|0x19||0x1C||0x04||APP file size|
The order of the sections in the header also is the order of them in the CIA file:
- certificate chain
- TMD file data
- APP file data
The data of the files is decrypted.