trezor-firmware/docs/bootloader.md

#TREZOR OS Bootloader

##Firmware file format

TREZOR OS firmware file consists of 3 parts:

1. vendor header
2. firmware header
3. firmware code

###Vendor Header

offset	length	name	description
0x0000	4	magic	firmware magic TRZV
0x0004	4	hlen	length of the vendor header (big endian)
0x0008	1	vsig_m	number of signatures needed to run the firmware from this vendor
0x0009	1	vsig_n	number of pubkeys vendor wants to use for signing
0x000A	1	vstr_len	vendor string length
0x000B	?	vstr	vendor string
?	?	vimg	vendor image (in TOIf format)
?	32	vpub1	vendor pubkey 1
...	...	...	...
?	32	vpubn	vendor pubkey n
?	64	slsig1	SatoshiLabs signature 1
?	64	slsig2	SatoshiLabs signature 2
?	64	slsig3	SatoshiLabs signature 3

###Firmware Header

offset	length	name	description
0x0000	4	magic	firmware magic TRZF
0x0004	4	hlen	length of the firmware header
0x0008	4	codelen	length of the firmware code
0x000C	1	vmajor	version (major)
0x000D	1	vminor	version (minor)
0x000E	1	vpatch	version (patch)
0x000F	1	vbuild	version (build)
0x0010	1	vidx1	vendor signature index 1
0x0011	32	vsig1	vendor signature 1
0x0043	1	vidx2	vendor signature index 2
0x0044	32	vsig2	vendor signature 2
...	...	...	...
?	1	vidxn	vendor signature index n
?	32	vsign	vendor signature n