Package2

Present in the firmware package titles (0100000000000819, 010000000000081A, 010000000000081B and 010000000000081C) and installed into eMMC storage's BCPKG2 partitions, "package2" contains the Switch kernel and the built-in system modules.

Format

Package2 is distributed in an already encrypted format. Therefore, it's not additionally encrypted when installed into the flash filesystem.

Offset	Size	Description
0x0	0x100	RSA-2048 signature (PKCS#1 v2.1 RSASSA-PSS-VERIFY with SHA256)
0x100	0x100	Encrypted header
0x200	Variable	Encrypted body

Encryption

Package2's contents are AES-CTR encrypted with a key known only by TrustZone.

The encrypted header's CTR is stored as it's first 0x10 bytes (offset 0x100). The encrypted body is divided in up to 4 sections, each one with a CTR stored inside the decrypted header.

Header

When decrypted, package2's header is as follows.

Offset	Size	Description
0x0	0x10	Header's CTR, official code copies the pre-decryption CTR over the decrypted result. Also used as metadata.
0x10	0x10	Section 0 CTR
0x20	0x10	Section 1 CTR
0x30	0x10	Section 2 CTR
0x40	0x10	Section 3 CTR
0x50	0x4	Magic "PK21"
0x54	0x4	Base offset
0x58	0x4	Always 0
0x5C	0x2	Version. HighByte must be <{maxver} and LowByte must be >{minver}, where {maxver} and {minver} are constants used by TZ updated with each package1 update.
0x5E	0x2	Padding
0x60	0x4	Section 0 size
0x64	0x4	Section 1 size
0x68	0x4	Section 2 size
0x6C	0x4	Section 3 size
0x70	0x4	Section 0 offset
0x74	0x4	Section 1 offset
0x78	0x4	Section 2 offset
0x7C	0x4	Section 3 offset
0x80	0x20	SHA-256 hash over encrypted section 0
0xA0	0x20	SHA-256 hash over encrypted section 1
0xC0	0x20	SHA-256 hash over encrypted section 2
0xE0	0x20	SHA-256 hash over encrypted section 3

Each section follows each other immediately and is encrypted with the same key used for encrypting the header. The section offsets are relative to a base, which is typically 0x80000000 pointing to the base of DRAM.

Before being decrypted, the encrypted header's CTR additionally encodes metadata used to validate package2's contents as follows:

• Size of the entire package2 with the raw header = ctr_word2 ^ ctr_word3 ^ ctr_word0
• Metadata version field = ((ctr_word1 ^ (ctr_word1 >> 16)) & 0xFF) ^ (ctr_word1 >> 24)

In [4.0.0], the metadata version field must be less or equal to 4.

Section 0

When decrypted, this section contains the plaintext Switch kernel binary.

Section 1

When decrypted, this section contains the built-in system modules encapsulated in a custom format.

INI1

Offset	Type	Description
0x0	u32	Magic "INI1"
0x4	u32	Size
0x8	u32	NumberProcesses (Must be <0x51)
0xC	u32	Padding (zero)

KIP1

Kernel Initial Process.

Offset	Type	Description
0x0	u32	Magic "KIP1"
0x4	char[12]	Name
0x10	u64	TitleId
0x18	u32	Process category (0: regular title, 1: kernel built-in). Should be 1 here.
0x1C	u8	Main thread priority
0x1D	u8	Default CPU core
0x1E	u8	Reserved (unused)
0x1F	u8	Flags: bit0-2: compression-enable for each section, when set. Bit3: Is64Bit. Bit4: IsAddrSpace36Bit. Bit5: [2.0.0+] UseSystemPoolPartition (1: System, 0: Application). Bit6, Bit7: reserved (unused)
0x20	#SectionHeader[6]	Sections: .text, .rodata, .data, .bss and two reserved (ignored) sections.
0x80	u32[0x20]	KernelCaps

SectionHeader

Offset	Type	Description
0x0	u32	OutOffset
0x4	u32	DecompressedSize
0x8	u32	CompressedSize
0xC	u32	Attribute: the size in pages of the main thread's stack for .rodata, reserved otherwise.

Compressed size can be 0 or lower than exepected, this is the case for BSS for example.

Compression

The compression used here is BLZ, with a modified footer since 3ds. The footer is now 0xC bytes instead of 0x8, and has the form u32 compressed_data_len; u32 initial_index; u32 additional_len_when_uncompressed;

Section 2

This section has a valid CTR and SHA-256 hash (over NULL) stored in the package2's header, but it's size is always 0. Likely reserved for future expansion.

Section 3

This section is not present (CTR and SHA-256 hash in package2's header are NULL). Likely reserved for future expansion.

Versions

System version	Package1 maxver constant	Package1 minver constant	Package2 version field
1.0.0	0x2	0x3	0x0104
2.0.0	0x3	0x4	0x0205
3.0.0	0x4	0x5	0x0306
3.0.2	0x5	0x6	0x0407
4.0.0	0x6	0x7	0x0508
5.0.0	0x7	0x8	0x0609
6.0.0	0x8	0x9	0x070A
6.2.0	0x9	0xA	0x080B

Public Keys

Exponent

0x10001

Retail Modulus

8D 13 A7 77 6A E5 DC C0 3B 25 D0 58 E4 20 69 59
55 4B AB 70 40 08 28 07 A8 A7 FD 0F 31 2E 11 FE
47 A0 F9 9D DF 80 DB 86 5A 27 89 CD 97 6C 85 C5
6C 39 7F 41 F2 FF 24 20 C3 95 A6 F7 9D 4A 45 74
8B 5D 28 8A C6 99 35 68 85 A5 64 32 80 9F D3 48
39 A2 1D 24 67 69 DF 75 AC 12 B5 BD C3 29 90 BE
37 E4 A0 80 9A BE 36 BF 1F 2C AB 2B AD F5 97 32
9A 42 9D 09 8B 08 F0 63 47 A3 E9 1B 36 D8 2D 8A
D7 E1 54 11 95 E4 45 88 69 8A 2B 35 CE D0 A5 0B
D5 5D AC DB AF 11 4D CA B8 1E E7 01 9E F4 46 A3
8A 94 6D 76 BD 8A C8 3B D2 31 58 0C 79 A8 26 E9
D1 79 9C CB D4 2B 6A 4F C6 CC CF 90 A7 B9 98 47
FD FA 4C 6C 6F 81 87 3B CA B8 50 F6 3E 39 5D 4D
97 3F 0F 35 39 53 FB FA CD AB A8 7A 62 9A 3F F2
09 27 96 3F 07 9A 91 F7 16 BF C6 3A 82 5A 4B CF
49 50 95 8C 55 80 7E 39 B1 48 05 1E 21 C7 24 4F

Debug Modulus

B3 65 54 FB 0A B0 1E 85 A7 F6 CF 91 8E BA 96 99
0D 8B 91 69 2A EE 01 20 4F 34 5C 2C 4F 4E 37 C7
F1 0B D4 CD A1 7F 93 F1 33 59 CE B1 E9 DD 26 E6
F3 BB 77 87 46 7A D6 4E 47 4A D1 41 B7 79 4A 38
06 6E CF 61 8F CD C1 40 0B FA 26 DC C0 34 51 83
D9 3B 11 54 3B 96 27 32 9A 95 BE 1E 68 11 50 A0
6B 10 A8 83 8B F5 FC BC 90 84 7A 5A 5C 43 52 E6
C8 26 E9 FE 06 A0 8B 53 0F AF 1E C4 1C 0B CF 50
1A A4 F3 5C FB F0 97 E4 DE 32 0A 9F E3 5A AA B7
44 7F 5C 33 60 B9 0F 22 2D 33 2A E9 69 79 31 42
8F E4 3A 13 8B E7 26 BD 08 87 6C A6 F2 73 F6 8E
A7 F2 FE FB 6C 28 66 0D BD D7 EB 42 A8 78 E6 B8
6B AE C7 A9 E2 40 6E 89 20 82 25 8E 3C 6A 60 D7
F3 56 8E EC 8D 51 8A 63 3C 04 78 23 0E 90 0C B4
E7 86 3B 4F 8E 13 09 47 32 0E 04 B8 4D 5B B0 46
71 B0 5C F4 AD 63 4F C5 E2 AC 1E C4 33 96 09 7B