The console-unique CTCert is used for signing CTX files, the DeviceCert used by eShop, and for DSiWare exports. This ECDSA signature, the ECDSA private key for this cert, and the IssuerID is loaded from memory initialized by bootrom instead of NAND. This is the 3DS equivalent of the DSi TWCert.
The CTCert is signed with ECDSA by Nintendo. CTCerts can be verified via a DER stored in NATIVE_FIRM, separate DERs are used for retail and dev/debug.
|0x00||0x04||Signature Type, 0x010005.|
|0x80||0x40||Cert Issuer ID, for retail this is "Nintendo CA - G3_NintendoCTR2prod", for dev "Nintendo CA - G3_NintendoCTR2dev"|
|0xC4||0x40||Key ID: "CT<DeviceId>-<ConsoleType>", where DeviceId is the hex DeviceId, and ConsoleType is 00 for retail, 01 for dev|
|0x104||0x04||Expiration time as UNIX Timestamp in big endian.|
|0x108||0x3C||ECDSA Public Key. This is two consecutive u8 arrays (each one of length 0x1E), where the first one corresponds to the ECDSA R coordinate, and the second to ECDSA S coordinate. These are in big endian.|
The ECDSA public key for this cert is converted from the ECDSA private key initialized by bootrom. The curve used for ECDSA is sect233r1.