N. Coesel wrote:
Chris Liechti wrote:
i don't need to transmit the password. a mass erase command only erases
the application and not the bootloader itself. but i don't plan to
encrypt the data anyway.
I don't quite follow this. Do you mean there is a way to let the mass erase
operation skip a section of internal flash?
only in my own boot laoder. the ROM BSL erases the entire flash.
(if i used a password, it would be the one of the application, not the
one of the boot loader)
if you realy want to encrypt the data, then some asymmetric algorithm
with private and public key would be good. each device could have it's
own private key, so that you can sell the updates per device.
Private/public keys algorithms are not usefull to protect firmware. If the
key is public, anyone could write some firmware for your device and upload
it to read the rest of the firmware.
unless you also use signing, where the device can verify the
authenticity of the firmware file.
> Private/public keys are intended to
send encrypted information to someone. You'll need an encryption method
where both sides need the exact key.
AES/Rijndael is a very good one and has not been compromised -yet-.
but there are "replacement BSLs" that allow higher baudrates and fix
some bugs of BSL version 1.1. these are often used with F14x devices.
they are loaded into RAM and executed from there.
These still need a mass erase before they can be loaded into RAM.
BTW, for absolute protection of the firmware, the JTAG fuse needs to be
blown as well.
Nico Coesel
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