Tickets are a format used to store an encrypted titlekey (using 128-Bit AES-CBC). With 3DS, the Ticket format was updated (now v1) from Wii/DSi format (v0).
All of the data in the file is represented in Big Endian.
Y denotes the total size of the "Signature Data" section and depends on the signature type.
The signature is of the ticket header.
|0x4 + X||Padding to align the signature data to 0x40 bytes|
|Value||Signature Method||Signature Size||Padding Size|
|0x010000||RSA_4096 SHA1 (Unused for 3DS)||0x200||0x3C|
|0x010001||RSA_2048 SHA1 (Unused for 3DS)||0x100||0x3C|
|0x010002||Elliptic Curve with SHA1 (Unused for 3DS)||0x3C||0x40|
|0x010005||ECDSA with SHA256||0x3C||0x40|
The hash for the signature is calculated over the Ticket Data.
|0x7C||0x1||Version (For 3DS this is always 1)|
|0x7F||0x10||TitleKey (normal-key encrypted using one of the common keyYs; see below)|
|0xA6||0x2||Ticket title version|
|0xB1||0x1||Index to the common keyY used for this ticket, usually 0x1 for retail system titles; see below.|
|0xDC||0x4||eShop Account ID?|
- For v0 of the format, see here
- The Ticket Title Version is generally the same as the title version stored in the Title Metadata. Although it doesn't have to match the TMD version to be valid.
- The titlekey is decrypted by using the AES engine with the ticket common-key keyslot. The keyY is selected through an index (ticket offset 0xB1) into a plaintext array of 6 keys ("common keyYs") stored in the data section of Process9. AES-CBC mode is used where the IV is the big-endian titleID. Note that on a retail unit index0 is a retail keyY, while on a dev-unit index0 is the dev common-key which is a normal-key. (On retail for these keyYs, the hardware key-scrambler is used)
- The titlekey is used to decrypt content downloaded from the CDN using 128-bit AES-CBC with the content index (as big endian u16, padded with trailing zeroes) as the IV.
- In demos, the first u32 in the "Limits" section is 0x4, then the second u32 is the max-playcount.
- The Content Index of a ticket has its own size defined within itself, with seemingly a minimal of 20 bytes, the second u32 in big endian defines the full value of X.
Tickets retrieved from CDN/SOAP have a certificate chain appended at the end of the file. There are two certificates in this chain:
|CERTIFICATE||SIGNATURE TYPE||RETAIL CERT NAME||DEBUG CERT NAME||DESCRIPTION|
|Ticket||RSA-2048||XS0000000c||XS00000009||Used to verify the Ticket signature|
|CA||RSA-4096||CA00000003||CA00000004||Used to verify the Ticket Certificate|
The CA certificate is issued by 'Root', the public key for which is stored in NATIVE_FIRM.
- CommonETicket (for short, cetk) is the name given to tickets for titles which are not available on the eShop, like system titles. As the name suggests, they are not unique tickets, the same ticket is common to each 3ds which has installed that title. This is in contrast to tickets for eShop content, which are generated prior to initial download, and are unique to 3ds it was generated for.
- CETK can be fetched through HTTP using the link to default update server, using the title's TMD URL where "cetk" is used instead of "tmd" for the URL. The 3DS NIM module retrieves system tickets via SOAP request GetSystemCommonETicket instead of directly downloading the cetks with HTTPS. The cetks are also accessible via HTTP (even though the 3DS never accesses them like that).