AES Registers

Registers

NAME	PHYSICAL ADDRESS	WIDTH	RW
REG_AESCNT	0x10009000	4	RW
REG_AESBLKCNT	0x10009004	4	W?
REG_AESWRFIFO	0x10009008	4	W
REG_AESRDFIFO	0x1000900C	4	R
REG_AESKEYSEL	0x10009010	1	RW
REG_AESKEYCNT	0x10009011	1	RW
REG_AESCTR	0x10009020	16	W
REG_AESMAC	0x10009030	16	W
REG_AESKEY0	0x10009040	48	W
REG_AESKEY1	0x10009070	48	W
REG_AESKEY2	0x100090A0	48	W
REG_AESKEY3	0x100090D0	48	W
REG_AESKEYFIFO	0x10009100	4	W
REG_AESKEYXFIFO	0x10009104	4	W
REG_AESKEYYFIFO	0x10009108	4	W

REG_AESCNT

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.

REG_AESBLKCNT

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

REG_AESWRFIFO/REG_AESRDFIFO

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.

REG_AESKEYCNT

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.

REG_AESCTR

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.

REG_AESMAC

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

Endianness and word order

When writing to the REG_AESCTR or REG_AESMAC register, the hardware will process the written data according to the current input endianness specified in AESCNT. 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.

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	DSiWare export key, and rest unknown.	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.	Only keyX/keyY.
0x24-0x2B	Never used?	Individually set.	Individually set.	Mixed.
0x2C-0x2F	Various uniques.	Same for all.	Same for all, probably.	No.
0x30-0x33	Various.	Same for all.	Same for all???	No.
0x34-0x37	Various uses.	Same for all.	Same for all, probably.	No.
0x38-0x3B	Various uses.	Same for all.	Different for all.	No.
0x3D-3F	Various uses.	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 scrambler instead (see below). There is no way to read the contents of a keyslot.

Keyslot	Description	KeyX	KeyY	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.	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
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 9.5.0-X keyslots 0x1B..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 NCCH key. Starting with 9.3.0-X.	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
0x25	v7.0 NCCH key.	NATIVE_FIRM boot.	NATIVE_FIRM.	-	Yes
0x2C	NCCH key.	Bootrom.	Process9.	-	Yes
0x2D	UDS local-WLAN CCMP key. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x2E	Unknown 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.	Bootrom(?), then later 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. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x37	Gamecard savedata actual key.	Bootrom.	NATIVE_FIRM.	-	Yes
0x38	Unknown. See EncryptDecryptAes.	Bootrom.	Bootrom.	-	Yes
0x39	Unknown. See 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
0x3D	Common key. Used to decrypt title keys in Ticket. Used by Gateway.	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.

keyX

The ARM9 bootrom initializes the keyX for certain 3DS keyslots, the ARM9 bootrom may also initialize the keyY for certain keyslots. In certain cases Process9 may also set the keyX.

Hardware key generator

A dedicated hardware key generator can be used to generate a keyslot's normalkey 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 used for key generation is unknown.

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.