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=== Overview ===
[[Category:File formats]]
CIA stands for '''C'''TR '''I'''mportable '''A'''rchive. 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.  
== Overview ==
CIA stands for '''C'''TR '''I'''mportable '''A'''rchive. This format allows the installation of titles to the 3DS. CIA files and titles on [[Title list|Nintendo's CDN]] contain identical data. As a consequence, valid CIA files can be generated from CDN content. This also means CIA files can contain anything that titles on Nintendo's CDN can contain.
 
Under normal circumstances CIA files are used where downloading a title is impractical or not possible. Such as distributing a [[Download Play]] child, or installing forced Gamecard updates. Those CIA(s) are stored by the titles in question, in an auxiliary [[NCCH#CFA|CFA]] file.
 
Development Units, are capable of manually installing CIA files via the [[3DS Development Unit Software#Dev Menu|Dev Menu]].
 
== Format ==
 
This is the current version of the CIA format, it was finalised in late 2010. (Older versions of the CIA format can be viewed on the [[Talk:CIA|Talk]] page)
 
The CIA format has a similar structure to the [http://wiibrew.org/wiki/Wad WAD format].


=== Format ===
The CIA format based on [http://wiibrew.org/wiki/Wad WAD format], so the structure is very similar to the WAD structure.
The file is represented in little-endian.
The file is represented in little-endian.
== CIA Header ==


This is a 32 bytes long header (8 x uint32).
The data is aligned in 64 byte blocks (if a content ends at the middle of the block, the next content will begin from a new block).
 
=== CIA Header ===


{| class="wikitable" border="1"
{| class="wikitable" border="1"
Line 17: Line 27:
|  0x00
|  0x00
|  0x04  
|  0x04  
|  Archive Header Size (=0x2020 bytes) (Starts with 0x80 @ offset 0x0020)
|  Archive Header Size (Usually = 0x2020 bytes)
|-
|-
|  0x04
|  0x04
|  0x04
|  0x02
|  Reserved = 0
|  Type
|-
|-
|  0x06
|  0x02
|  Version
|-
|  0x08     
|  0x08     
|  0x04
|  0x04
Line 29: Line 43:
|  0x0C       
|  0x0C       
|  0x04
|  0x04
|  Ticket size
|  [[Ticket]] size
|-
|-
|  0x10     
|  0x10     
|  0x04
|  0x04
|  TMD file size
|  [[TMD]] (Title Metadata) file size
|-
|-
|  0x14     
|  0x14     
|  0x04
|  0x04
|  Banner size (0 if no banner)
|  Meta size (0 if no Meta data is present)
|-
|-
|  0x18     
|  0x18     
|  0x04
|  0x08
|  Content Size
|  Content size
|-
|-
|  0x1C
|  0x20
|  0x04
|  0x2000
|  APP file size
|  Content Index
|}
|}


The order of the sections in the header also is the order of them in the CIA file:
The order of the sections in the CIA file:
* certificate chain
* certificate chain
* Ticket
* Ticket
* TMD file data
* TMD file data
* APP file data
* Content file data
The data of the files is decrypted.
* Meta file data (Not a necessary component)
 
The contents (NCCH/SRL) are encrypted using 128-bit AES-CBC. The encryption uses the decrypted titlekey from the [[Ticket#Structure|ticket]], and the content index from the TMD padded with zeros as the IV.
 
=== Certificate Chain ===
 
There are three [[Certificates|certificates]] in this chain:
 
{| class="wikitable" border="1"
|-
!  CERTIFICATE
!  SIGNATURE TYPE
!  RETAIL CERT NAME
!  DEBUG CERT NAME
!  DESCRIPTION
|-
|  CA
|  RSA-4096
|  CA00000003
|  CA00000004
|  Used to verify the Ticket/TMD Certificates
|-
|  Ticket
|  RSA-2048
|  XS0000000c
|  XS00000009
|  Used to verify the Ticket signature
|-
|  TMD
|  RSA-2048
|  CP0000000b
|  CP0000000a
|  Used to verify the TMD signature
|}
 
The CA certificate is issued by 'Root', the public key for which is stored in NATIVE_FIRM.
 
=== Meta ===
 
The structure of this data is as follows:
 
{| class="wikitable" border="1"
|-
!  START
!  SIZE
!  DESCRIPTION
|-
|  0x00
|  0x180
|  Title ID dependency list - Taken from the application's [[NCCH/Extended Header|ExHeader]]
|-
|  0x180
|  0x180
|  Reserved
|-
|  0x300
|  0x4
|  Core Version
|-
|  0x304
|  0xFC
|  Reserved
|-
|  0x400
|  0x36C0
|  [[SMDH|Icon Data]](.ICN) - Taken from the application's [[ExeFS]]
|}
 
Obviously this section is not present in TWL CIA files, or any other CIA file which does not contain a [[NCCH#CXI|CXI]].
 
== Tools ==
 
* [https://github.com/3dshax/ctr/tree/master/ctrtool ctrtool] - Reading/Extraction of CIA files. This can only decrypt the title-key for development CIAs, since retail CIAs use the [[AES]] hardware key-scrambler for the common-key keyslot.
 
* [https://github.com/Tiger21820/ctr_toolkit/tree/master/make_cia make_cia] - Generating CIA files. Requires CommonKey and ticket/TMD RSA-2048 private exponents.
 
* [https://github.com/Tiger21820/ctr_toolkit/tree/master/make_cdn_cia make_cdn_cia] - (CMD)(Windows/Linux) Generates CIA files from CDN Content
 
* [[makerom]] - Tool which can be used to create NCCH, CCI, and CIA files.
 
== Title Key Encryption ==
 
The unencrypted Title Key is used to encrypt the data in a CIA. The encrypted Title Key of a CIA can be found at offset 0x1BF in a CIA's Ticket.
Each Title Key is encrypted with AES-CBC to get the encrypted Title Key.
 
To encrypt an unencrypted title key, you need:
 
* Common key (as byte array)
* Title ID (as ulong)
* (and of course the unencrypted title key you want to encrypt) (as byte array)
 
The title key encryption process starts by converting the ulong (Title ID) into a byte array using by retrieving the bytes of the Title ID using BitConverter.GetBytes().
If the converted bytes (title ID) are in Little Endian, reverse those bytes. (in C# it would be Array.Reverse(byte_array_from_bitconverter))
This process makes the Title Key encryption IV.
 
Next, after you've gotten your Title Key's IV, you can start your cryptography transformation. Using AESManaged, where:
 
Key  = Common Key
 
IV  = the byte array found in the conversion process above
 
Mode = CipherMode.CBC
 
Create the encryptor (AesManaged.CreateEncryptor(key, iv)) where the key and IV are both the same as above.
 
Then, create a CryptoStream and a MemoryStream. The Crypto stream should start with the arguments (memorystream, aes_transform_from_above, CryptoStreamMode.Write).
 
Write to the CryptoStream where buffer=unencrypted_titlekey, offset=0, and count=the length of the unencrypted title key.
 
Use FlushFinalBlock() on the CryptoStream.
 
Finally, then, the encrypted title key will be available from your memory
stream. (to output the calculated encrypted title key as a byte array, you can use memorystream.ToArray(), for example)


If you sum up all the fields in the header you get 60 bytes less then the actual file size. (you need to add the 32 bytes of the header).
Example function: (C#)


Question: Where are those 60 bytes at?
<pre>
        public static byte[] EncryptMyTitleKey(byte[] commonKey, byte[] titleKey, ulong titleId)
        {
            // Make encryption IV
            byte[] titleidasbytes = new byte[0x10];
            for (int i = 0; i < 0x10; i++)
            {
                titleidasbytes[i] = 0;
            }
            byte[] bitBytes = BitConverter.GetBytes(titleId);
            if (BitConverter.IsLittleEndian)
            {
                Array.Reverse(bitBytes);
            }
            bitBytes.CopyTo(titleidasbytes, 0);
            // Encrypt
            ICryptoTransform transform = new AesManaged { Key = commonKey, IV = titleidasbytes, Mode = CipherMode.CBC }.CreateEncryptor(commonKey, titleidasbytes);
            MemoryStream memstream = new MemoryStream();
            CryptoStream cryptostream = new CryptoStream(memstream, transform, CryptoStreamMode.Write);
            cryptostream.Write(titleKey, 0, titleKey.Length);
            cryptostream.FlushFinalBlock();
            return memstream.ToArray();
        }
</pre>
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