Lotus3

Lotus3 is the Gamecard ASIC, which is a separate chip on the motherboard responsible for communicating with the Gamecard.

It is the Tegra's SDMMC2 device on the Switch and FS communicates with it using a custom protocol based on vendor specific MMC commands.

Protocol

All communication is done using custom MMC_SEND_MANUFACTURER commands.

Value	Description
60	WriteOperation
61	FinishOperation
62	Sleep
63	UpdateKey

WriteOperation

Sends a Gamecard ASIC operation.

FinishOperation

Returns the status of a completed Gamecard ASIC operation.

Sleep

Puts the Gamecard ASIC in sleep mode.

UpdateKey

Tells the Gamecard ASIC to generate new random key data.

AsicOperation

Offset	Size	Description
0x0	0x1	OperationId
0x1	0x1F	OperationData
0x20	0x20	CvValue (secure mode only)

OperationId

The Gamecard ASIC supports a total of 20 operation commands. These commands are passed to the ASIC using the WriteOperation MMC command.

Additional data buffers are then read/written as pages of 0x200 bytes each, using standard MMC read/write commands.

Value	Description
0x01	SendFirmware
0x02	ReceiveCertificate
0x03	SendSocCertificate
0x04	ReceiveRandomValue
0x05	SendRandomValue
0x06	ReceiveDeviceChallenge
0x07	RespondDeviceChallenge
0x08	SendHostChallenge
0x09	ReceiveChallengeResponse
0x0A	ChangeModeToSecure
0x0B	WriteRegister
0x0C	ReadRegister
0x0D	ChangeGcModeToDebug
0x0E	GetCardHeader
0x0F	ChangeGcModeToSecure
0x10	SendCardCommand
0x11	EnableCardBus
0x12	ExchangeRandomValuesInSecureMode
0x13	ReadRmaInformation
0x14	[9.0.0+] ChallengeCardExistence

SendFirmware

Signals the Gamecard ASIC to receive the firmware.

This is the only operation handled by the Gamecard ASIC's bootrom.

ReceiveCertificate

Signals the Gamecard ASIC to send the ASIC's certificate.

SendSocCertificate

Signals the Gamecard ASIC to receive the certificate from GetGameCardCertificate.

ReceiveRandomValue

Signals the Gamecard ASIC to send a RSA-OAEP encrypted message to be decrypted by the host library.

The decrypted message will be used to generate a common AES-128 (CBC and CTR) key and IV/CTR shared between the ASIC and the host library.

SendRandomValue

Signals the Gamecard ASIC to receive a RSA-OAEP encrypted message to be decrypted by the ASIC.

The decrypted message will be used to generate a common AES-128 (CBC and CTR) key and IV/CTR shared between the ASIC and the host library.

ReceiveDeviceChallenge

Signals the Gamecard ASIC to send AES-128-CBC encrypted authentication data to be decrypted and hashed by the host library.

RespondDeviceChallenge

Signals the Gamecard ASIC to receive the AES-128-CBC encrypted hash of the ASIC authentication data.

SendHostChallenge

Signals the Gamecard ASIC to receive AES-128-CBC encrypted authentication data to be decrypted and hashed by the ASIC.

ReceiveChallengeResponse

Signals the Gamecard ASIC to send the AES-128-CBC encrypted hash of the library authentication data.

ChangeModeToSecure

Signals the Gamecard ASIC to enter secure mode.

In secure mode, all communication with the Gamecard ASIC must be AES-128-CTR encrypted.

WriteRegister

Signals the Gamecard ASIC to write an internal register.

OperationData becomes:

Offset	Size	Description
0x0	0x3	Reserved
0x3	0x4	RegisterAddress
0x7	0x18	Reserved

RegisterValue is passed in a data page.

ReadRegister

Signals the Gamecard ASIC to send the contents of its registers.

ChangeGcModeToDebug

Signals the Gamecard ASIC to change into debug mode and send information on the current Gamecard.

GetCardHeader

Signals the Gamecard ASIC to send the current Gamecard's header.

ChangeGcModeToSecure

Signals the Gamecard ASIC to enable secure communication with the Gamecard and return its key area.

SendCardCommand

Signals the Gamecard ASIC to relay commands to the Gamecard.

OperationData becomes:

Offset	Size	Description
0x0	0x1	PageSize
0x1	0x1	Direction (0 = Read, 1 = Write)
0x2	0x1	Reserved
0x3	0x4	PageNumber
0x7	0x10	CardCommand
0x17	0x8	Reserved

EnableCardBus

Signals the Gamecard ASIC to enable the Gamecard's bus line.

ExchangeRandomValuesInSecureMode

Signals the Gamecard ASIC to exchange random authentication values with the current Gamecard.

OperationData becomes:

Offset	Size	Description
0x0	0x1F	RandomValues

The Gamecard's response is returned in a data page.

ReadRmaInformation

Signals the Gamecard ASIC to send information on the Gamecard ASIC. This is called by GetGameCardAsicInfo.

ChallengeCardExistence

Signals the Gamecard ASIC to exchange random values with the current Gamecard.

OperationData becomes:

Offset	Size	Description
0x0	0x1F	RandomValues

The Gamecard's response is returned in a data page.

AsicRegisters

Offset	Size	Description
0x0	0x4	Lotus3Status
0x4	0x4	AccCtrl1
0x8	0x4	Wait1TimeRead
0xC	0x4	Wait2TimeRead
0x10	0x4	Wait1TimeWrite
0x14	0x4	Wait2TimeWrite
0x18	0x4	PageRemainder
0x1C	0x4	LatencyTime
0x20	0x4	LimArea
0x24	0x4	CupVersion
0x28	0x4	Lotus3Version
0x2C	0x4	Standby2

CardHeader

Offset	Size	Description
0x0	0x4	CupVersion
0x4	0x4	CardId1
0x8	0x100	CardHeader (without the signature)
0x108	0xD8	Reserved
0x1E0	0x20	[11.0.0+] SHA-256 hash of the data from 0 to 0x1E0 ([1.0.0-10.2.0] Reserved)

CardKeyArea

Offset	Size	Description
0x0	0x4	SecurityLevel
0x4	0x4	Lotus3Status
0x8	0x4	CardId1
0xC	0x4	CardId2
0x10	0x40	CardUid
0x50	0x1B0	Reserved
0x200	0x200	CertArea
0x400	0x200	Reserved
0x600	0x200	InitialData

[11.0.0+] This is now:

Offset	Size	Description
0x0	0x4	SecurityLevel
0x4	0x4	Lotus3Status
0x8	0x4	CardId1
0xC	0x4	CardId2
0x10	0x40	CardUid
0x50	0x1B0	Reserved
0x200	0x200	CertArea
0x400	0x200	InitialData

CardUid

Offset	Size	Description
0x0	0x1	MakerId
0x1	0x1
0x2	0x1
0x3	0xD	UniqueData
0x10	0x1	Reserved (always 0)
0x11	0xB	Reserved (always all 0xFF)
0x1C	0x4	CardId1Mirror
0x20	0x20	Hash

MakerId

Value	Description
0	MegaChips (Macronix)
1	Lapis
2

UniqueData

While presumed to be random, this field actually has some degree of determinism depending on the MakerId.

MakerId 0:

Offset	Size	Description
0x0	0x1	Type (4 = T1RomLate, 8 = T1RomFast)
0x1	0x1	Line (0x21 for T1RomLate, incrementing value for T1RomFast)
0x2	0x3	Id
0x5	0x2	X (16-bit coordinate?)
0x7	0x2	Y (16-bit coordinate?)
0x9	0x4	Random

MakerId 1:

Offset	Size	Description
0x0	0x2	Line (incrementing value)
0x2	0x3	Id
0x5	0x1
0x6	0x1	Version (0 or 1)
0x7	0x2
0x9	0x4	Random

MakerId 2:

Offset	Size	Description
0x0	0x4	Random
0x4	0x1
0x5	0x1
0x6	0x4	Id (ASCII string)
0xA	0x1
0xB	0x1
0xC	0x1

CardId1Mirror

This field mirrors bit 5 of the MemoryType field from the CardId1.

CardCommand

Offset	Size	Description
0x0	0x1	CommandId
0x1	0xF	CommandData

CommandId

These commands are issued by the Gamecard ASIC to the actual Gamecard using the OperationData passed to SendCardCommand.

Additional data buffers are then read/written as pages of 0x200 bytes each, using standard MMC read/write commands.

Value	Description
0x6	SelfRefresh
0xF	T1ReadUid
0x10	DebugReadId1
0x11	DebugReadId2
0x12	DebugReadId3
0x13	DebugReadUid
0x15	DebugReadCrc
0x16	DebugWritePage
0x17
0x18	DebugErase
0x19	DebugReadParameter
0x20	DebugWriteParameter
0x21	T1ReadPage
0x22
0x28	ReadId2
0x2E	ForceErase
0x30	T1ReadId3
0x39	T1SetKey
0x56	ReadId1
0x59
0x5B	ReadPage
0x67	T1ReadId1
0x83	T1WritePage
0x8A
0xA5	ReadId3
0xB8	T1Refresh
0xC4	T1ReadId2
0xE0	ReadInitialData
0xE2	ChangeInitialData
0xE3	T2ReceiveCertificate
0xE4	T2SendSocCertificate
0xE5
0xE6	T2ReceiveRandomValue
0xE7	T2SendRandomValue
0xE8	T2ReceiveDeviceChallenge
0xE9	T2RespondDeviceChallenge
0xEA	T2SendHostChallenge
0xEB	T2ReceiveChallengeResponse
0xEC
0xED
0xEE
0xEF
0xF1
0xFA	ReadRefreshStatus

AsicFirmware

This is the Gamecard ASIC's user firmware (Lotus ASIC Firmware or LAFW) uploaded through the SendFirmware operation.

Offset	Size	Description
0x0	0x100	RSA-2048 PKCS #1 signature over the firmware (data from 0x100 to 0x7800)
0x100	0x4	Magic ("LAFW")
0x104	0x1	ProductionFirmwareFlag
0x105	0x1	DevelopmentFirmwareFlag
0x106	0x1	WriterFirmwareFlag
0x107	0x9	Reserved
0x110	0x8	FirmwareVersion
0x118	0x4	FirmwareSize
0x11C	0x4	Reserved
0x120	0x10	Iv
0x130	0x10	Lotus3DeviceId
0x140	0x40	Reserved
0x180	0x7680	FirmwareData

FirmwareVersion

Bits	Description
0-61	Version (0, 0x1, [4.0.0+] 0x3, [9.0.0+] 0x7, [11.0.0+] 0xF, [12.0.0+] 0x1F)
62	IsDevelopment
63	IsProduction

Anti-downgrade

Loading a firmware blob will burn as many OTP fuses as those specified by the Version field. This will lock the Gamecard ASIC to only allow running firmware blobs with the same or higher version number.