ChunkSIGN.hexpat

// Structure and purpose based on theory. Nothing yet verified.

// keyIndex is an index known internally by Roblox, corresponding to a private
// key. An FFlag configures Studio to select a specific index.
//
// Possible FFlag candidate is "KeyRing". Currently, it has a value of 10, while
// DataModelPatch.rbxm contains signatures for indices 9 to 12.

struct Signature {
    u32 version;      // Zeroed. Possibly version reserved for format changes.
    u32 keyIndex;     // Possibly index of private key.
    u32 reserved;     // Zeroed. Possibly high bits of keyIndex.
    u32 length;       // Length of signature value.
    u8 value[length]; // Possibly the signature value itself.
};

// Contains signatures of signed data for multiple private keys.
struct Signatures {
    u32 length;
    Signature signatures[length];
};

// Standard RBXL chunk format. Typically uncompressed.
struct ChunkSIGN {
    char sig[4];
    if (sig != "SIGN") {
        error("entrypoint must start at SIGN chunk signature");
    }
    u32 compressedLength;
    u64 uncompressedLength;
    Signatures payload;
};

// For DataModelPatch.rbxm of Studio version-2ba85a75f8114838
ChunkSIGN main @ 0x0058C81D;