Secure firmware upgrade: ecryption

[hisham23]

Posted on May 23, 2012 at 09:33

Hello,

I read this application note about secure firmware upgrade http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/APPLICATION_NOTE/DM00044227.pdf

So i want to ask about the encryption method that is used in such application.

Regards,

Hisham

[Tesla DeLorean]

Posted on May 23, 2012 at 15:29

I believe it uses AES-128

[hisham23]

Posted on May 24, 2012 at 06:53

So do you mean that i first build my code, so i get unencrypted hex file.

Then i make a software using java or vb that takes the unencrypted hex file and uses AES algorithm to encrypt the file then output encrypted hex file.

Is this right?

[Tesla DeLorean]

Posted on May 24, 2012 at 10:37

That's certainly one approach.

You can use any algorithm you choose, ST has used AES-128 for it's firmwares in the past (ST-Link), and has HW support in the STM32F41x parts, and software libraries for the others. It might be easier just to download source from the web than jump through the hoops ST has erected.

I'd probably encapsulate the firmware image in a binary form, with headers and checksums, rather than hex, and wouldn't use VB/Java, but use whatever means/methods you are comfortable with.