AES Registers

Registers

Old3DS	Name	Address	Width	RW
Yes	AES_CNT	0x10009000	4	RW
Yes	AES_BLKCNT	0x10009004	4	W?
Yes	AES_WRFIFO	0x10009008	4	W
Yes	AES_RDFIFO	0x1000900C	4	R
Yes	AES_KEYSEL	0x10009010	1	RW
Yes	AES_KEYCNT	0x10009011	1	RW
Yes	AES_CTR	0x10009020	16	W
Yes	AES_MAC	0x10009030	16	W
Yes	AES_KEY0	0x10009040	48	W
Yes	AES_KEY1	0x10009070	48	W
Yes	AES_KEY2	0x100090A0	48	W
Yes	AES_KEY3	0x100090D0	48	W
Yes	AES_KEYFIFO	0x10009100	4	W
Yes	AES_KEYXFIFO	0x10009104	4	W
Yes	AES_KEYYFIFO	0x10009108	4	W

AES_CNT

Bit	Description
4-0	Write FIFO count (0-16)
9-5	Read FIFO count (0-16)
10	Flush write FIFO (1=Clear write FIFO)
11	Flush read fifo (1=Clear read FIFO)
18-16	MAC size (encoding = (maclen-2)/2)
19	? (MAC related)
20	MAC input control (0 = read MAC from FIFO, 1 = read from MAC register)
21	MAC status (0 = invalid, 1 = verified)
22	Output endianness (1=Big endian, 0=Little endian)
23	Input endianness (1=Big endian, 0=Little endian)
24	Output word order (1=Normal order, 0=Reversed order)
25	Input word order (1=Normal order, 0=Reversed order)
26	Update keyslot (selects the keyslot specified by REG_AESKEYSEL when this bit is set)
29-27	Mode (0=CCM decrypt, 1=CCM encrypt, 2=CTR, 3=CTR, 4=CBC decrypt, 5=CBC encrypt, 6=ECB decrypt, 7=ECB encrypt)
30	Interrupt enable (1=enable, 0=disable)
31	Start (1=enable/busy, 0=idle)

When bit31 is clear, the AES engine will handle keyslot-selection when bit26 is set immediately. When bit31 is set, the AES engine won't handle bit26 immediately, instead the AES engine will automatically handle the already-set bit26 once bit31 clears(current AES operation finishes).

Clearing bit31 while the AES engine is doing crypto will result in the AES engine stopping crypto, once it finishes processing the current block.

AES_BLKCNT

Bit	Description
16-31	(Data length)>>4

AES_WRFIFO/AES_RDFIFO

Up to 128 bytes of input data can be buffered.

The input data for the AES crypto operation is written to REG_AESWRFIFO, the output data is read from REG_AESRDFIFO.

Reading from REG_AESRDFIFO when there's no data available in the RDFIFO will result in reading the last word that was in the RDFIFO.

AES_KEYCNT

Bit	Description
5-0	Keyslot
6	Hardware key-generator type: 0 = 3DS, 1 = DSi.
7	This normally has value 1 written here when updating keys. 0 = disable key FIFO flush, 1 = enable key FIFO flush.

Bit6 is only used when keyslots >=4 are used, value1 has the same affect as doing key-init with the TWL keyslots. Bit6 is only checked when a keyY was completely written, for when the final-normalkey needs updated via the key-generator. Changing bit6 has no affect on the generated normalkey when writing to this bit immediately after writing the last keyY word.

AES_CTR

This register specifies the counter (CTR mode), nonce (CCM mode) or the initialization vector (CBC mode) depending on the mode of operation. For CBC and CTR mode this register takes up the full 16 bytes, but for CCM mode the nonce is only the first 12 bytes. The AES engine will automatically increment the counter up to the maximum BLKCNT, after which point it must be manually incremented and set again.

AES_MAC

This register specifies the message authentication code (MAC) for use in CCM mode.

AES_KEY0/1/2/3

These registers are the same as they were on TWL, and are likely preserved for compatibility reasons. The keyslot is updated immediately after *any* data(u8/u32/...) is written here, which was used on DSi to break the key-generator.

Endianness and word order

When writing to the AES_CTR or AES_MAC register, the hardware will process the written data according to the current input endianness specified in AES_CNT. However, the current specified input word order will not be honored for this register, and always defaults to reversed word order. Therefore, for normal word order, the reversal must be carried out manually if required.

Keyslot ranges

This is approximately a table of what is set by bootrom before booting into FIRM. Often it appears that keyslots in groups of 4 have the same keyX, and sometimes also same keyY set.

Byte	Description
0-15	Normalkey
16-31	KeyX
32-47	KeyY

Keyslot	Name	KeyX	KeyY/Normal-key	Console unique.
0x00-0x03	TWL keys.	Probably unset.	Probably unset.	-
0x04-0x07	NAND partition keys.	Same for all.	Different for all.	Yes
0x08-0x0B	See below.	Same for all.	Different for all.	Yes
0x0C-0x0F	SSL cert key.	Same for all.	Same for all.	No
0x10-0x17	-	Not set.	Not set.	-
0x18-0x1B	Never used.	Same for all.	Same for all.	Yes
0x1C-0x1F	Never used.	Same for all.	Same for all.	Yes
0x20-0x23	Never used.	Same for all.	Same for all.	Normalkey is not. keyX is. keyY unknown.
0x24	Never used.	Individually set.	Individually set.	Normalkey is not. keyX is. keyY unknown.
0x25-0x27	-	Not set.	Not set.	-
0x28-0x2B	Never used.	Individually set.	Individually set.	Normalkey is not. keyX is. keyY unknown.
0x2C-0x2F	Various uniques.	Same for all.	Same for all, probably.	No
0x30-0x33	Various uniques.	Same for all.	Same for all, probably.	No
0x34-0x37	Various uniques.	Same for all.	Same for all, probably.	No
0x38-0x3B	Various uniques.	Same for all.	Different for all.	No
0x3C-0x3F	Various uniques.	Individually set.	Individually set.	No

Keyslot pairs (0x24, 0x28) and (0x38, 0x3C) shares the same normal-key, while at the same time having different keyX's. This suggests they were set to same normal-key by bootrom.

Keyslots

There are 0x40 keyslots, each of which stores three keys called keyX, keyY and normalkey. All keys can be set explicitly, but the normalkey can optionally be generated using a hardware key generator instead (see below). There is no way to read the contents of a keyslot.

Keyslot	Description	KeyX set by	KeyY set by	Normal-key	Old3DS
0x00-0x03	TWL keys.	NATIVE_FIRM hard-boot.	NATIVE_FIRM hard-boot.	-	Yes
0x04..0x07	NAND partition keys. Keyslot is determined by NCSD partition FS type and encryption type. The New3DS Process9 sets the keyY for keyslot 0x05 (New3DS CTRNAND) to a key from .(ro)data. Its keyX is console-unique and set by the bootloader.	Bootrom.	Bootrom.	-	Yes
0x0A	DSiWare export key. Used for encrypting the all-zero 0x10-byte block in the DSiWare_Exports header. Console-unique.	See above keyslot info.	See above keyslot info.	-	Yes
0x0B	This is console-unique. This keyslot is used for the NAND dbs images AESMACs, and the Nand/private/movable.sed AESMAC(when used).	See above keyslot info.	See above keyslot info.	-	Yes
0x0D	SSL-certificate key. See EncryptDecryptAes.	-	-	Bootrom.	Yes
0x11	Temporary keyslot. Used by FIRM for general normal-key crypto. Also used by the New3DS FIRM arm9 binary loader.	Arm9Loader.	Arm9Loader.	NATIVE_FIRM.	Yes
0x14	Starting with 5.0.0-11, NATIVE_FIRM Process9 now sets the keyY for this to the same one it uses for initializing 3 of the keyslots' keyYs from here.	Bootrom.	NATIVE_FIRM boot.	-	Yes
0x15	Used/initialized by the New3DS arm9 binary loader, see here.	Arm9Loader.	Arm9Loader.	See previous info for this keyslot.	No
0x16	Used/initialized by the New3DS arm9 binary loader starting with 9.5.0-X, see here.	Arm9Loader.	Arm9Loader.	See previous info for this keyslot.	No
0x18..0x1F	These are the New3DS keyslots, where the keyX is generated with keyslot 0x11 by the New3DS arm9 binary loader. As of FIRM 9.6.0-X keyslots 0x1C..0x1F are not yet used by Process9.	Arm9Loader.	NATIVE_FIRM / see previous info for these keyslots.	See previous info for these keyslots.	No
0x18	New3DS 9.3.0-X NCCH key, when ncchflag[3] is 0x0A.	Arm9Loader.	NATIVE_FIRM	-	No
0x19	New3DS gamecard savedata AES-MAC key. Equivalent of keyslot 0x33, used when a NCSD flag is set to a certain value (implemented with 9.3.0-X).	Arm9Loader.	NATIVE_FIRM	-	No
0x1A	New3DS gamecard savedata actual key. Equivalent of keyslot 0x37, used when a NCSD flag is set to a certain value (implemented with 9.3.0-X).	Arm9Loader.	NATIVE_FIRM	-	No
0x1B	New3DS 9.6.0-X NCCH key, when ncchflag[3] is 0x0B.	Arm9Loader.	NATIVE_FIRM	-	No
0x24	AGB_FIRM savegame AES-MAC key.	Bootrom.	AGB/NATIVE_FIRM.	-	Yes
0x25	v7.0 NCCH key, when ncchflag[3] is 0x01.	NATIVE_FIRM boot.	NATIVE_FIRM.	-	Yes
0x2C	Original NCCH key, when ncchflag[3] is 0x00 and always for certain NCCH sections.	Bootrom.	Process9.	-	Yes
0x2D	UDS local-WLAN CCMP key. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x2E	Streetpass key. See EncryptDecryptAes.	Bootrom.	NATIVE_FIRM.	-	Yes
0x2F	v6.0 save key.	Bootrom.	NATIVE_FIRM.	-	Yes
0x30	SD/NAND AES-MAC key. This keyY is initialized via movable.sed. This is used for calculating the AESMACs under SD /Nintendo 3DS/<ID0>/<ID1>/ (except DSiWare_Exports) and NAND /data/.	Bootrom.	NATIVE_FIRM.	-	Yes
0x31	APT wrap key. See EncryptDecryptAes. NATIVE_FIRM sets this keyY to the same one used for keyslot 0x2E.	Bootrom.	NATIVE_FIRM.	-	Yes
0x32	Unknown. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x33	Gamecard savedata AES-MAC.	Bootrom.	NATIVE_FIRM.	-	Yes
0x34	SD key. This keyY is initialized via movable.sed. This is used for encrypting *all* SD card data under /Nintendo 3DS/<ID0>/<ID1>/.	Bootrom.	NATIVE_FIRM.	-	Yes
0x35	Movable.sed key. This is the keyslot used for movable.sed encryption + AES-MAC with the import/export commands.	Bootrom.	Bootrom.	-	Yes
0x36	Unknown. Used by friends module. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x37	Gamecard savedata actual key.	Bootrom.	NATIVE_FIRM.	-	Yes
0x38	BOSS key. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x39	Download Play key, and the actual NFC key for generating retail Amiibo keys. This keyslot is used for two different keys. Both are available via EncryptDecryptAes. NATIVE_FIRM sets this keyY to the same one used for keyslot 0x2E.	Bootrom.	NATIVE_FIRM.	-	Yes
0x3A	DSiWare export key. This keyY is initialized via movable.sed. This is used for calculating the AESMACs for SD DSiWare_Exports.	Bootrom.	NATIVE_FIRM.	-	Yes
0x3B	CTR-CARD hardware-crypto seed decryption key. AES-CCM is used, the keyY, nonce and MAC are stored in the Card Info Header.	Bootrom.	NATIVE_FIRM.	-	Yes
0x3D	Common key. Used to decrypt title keys in Ticket.	Bootrom.	NATIVE_FIRM.	-	Yes

Updating keydata

The contents of the keyslot specified in REG_AESKEYCNT can be updated by consecutively writing four words to REG_AESKEYXFIFO (keyX), REG_AESKEYYFIFO(keyY), or REG_AESKEYFIFO (normalkey).

After writing to a keyslot, the keyslot must be selected again(write REG_AESKEYSEL + set REG_AESCNT bit26), even when writing to the same keyslot. Writing the last word to a key FIFO immediately after selecting a keyslot will not affect the keyslot keydata that gets used at that time, the new keydata will not get used until the keyslot gets selected again.

Writing to the key FIFOs with byte writes results in the AES engine converting the byte to a word for setting the key word, with this: word = (byteval) | (byteval<<8) | (byteval<<16) | (byteval<<24). The result is the same regardless of which FIFO register byte was written to.

The TWL keyslots 0x00-0x03 can be set directly by writing to the REG_AESKEY0-REG_AESKEY3 registers.

The key FIFOs can be written simultaneously. For example, executing the following 4 times will result in the keyX and keyY being set to all-zero(unknown for normalkey): memset(0x10009100, 0, 0x100);

Each key FIFO has a 0x10-byte tmp-buffer for storing the words written to that FIFO. Once the last word is written to a key FIFO, the filled tmp-buffer is then written to the key-data for the keyslot selected by REG_AESKEYCNT at the time the last word was written.

Hardware key generator

A dedicated hardware key generator can be used to generate a keyslot's normal-key from its keyX and keyY. The hardware key generator is triggered by writing the keyY, which is the only way to trigger it with the 3DS keyslots.

The algorithm for generating the normal-key from keyX and keyY is as follows, in big-endian 128-bit unsigned wraparound arithmetic:

Mode	Formula	Secret Constant C
3DS	NormalKey = (((KeyX ROL 2) XOR KeyY) + C) ROR 41	Not publicly disclosed.
DSi	NormalKey = ((KeyX XOR KeyY) + C) ROL 42

Unless noted otherwise, all keyslots on retail units use the hardware key generator.

FIRM-launch key clearing

Starting with 9.0.0-20 the Process9 FIRM-launch code now "clears" the following AES keyslots, with certain keydata by writing the normal-key: 0x15 and 0x18-0x20. These are the keyslots used by the New3DS FIRM arm9bin loader(minus keyslot 0x11), the New3DS Process9 does this too.