Secure DFU serial bootloader

[Erwin v. H.]

I'm busy implementing a (serial) DFU host, but sofar i'm unable to send a proper init packet.

The bootloader keeps returning an invalid signature error

If i open a .dat file with HxD is the visible data also in the order that it has to be send or do i have to modify this?

Yours sincerely,

Erwin

Application.dat

[tesc]

Hi,

What version of the DFU bootloader is on the DFU target, based on what version of the SDK?

How do you generate the DFU update package?

Are you using Secure DFU, and have you signed the update using the correct private key?

Regards,
Terje

[Erwin v. H.]

The bootloader is based on SDK 15.3 and I generated the update package an public key with the same private key (nRF utility)

Regards,

Erwin

[Erwin v. H.]

Dear,

Do you have any idea how i can continue.

As is said i currently always get a signature error after sending the init packet.

Do i have to search it in the method of sending or in a mismatch of signature/private key between the generated package and bootloader?

Regards,

Erwin

[tesc]

Hi,

So to be clear, the update package should be generated using the private key, and the bootloader is made using the corresponding public key.

While I am not familiar with HxD, the data should be sent in the same order it appears in the .dat file, which I presume is the same as what is displayed in any hex editor. (I.e. endianness is kept as written to file by nrfutil when generating the dfu package. / The binary data files in the zip are to be treated as a stream of bytes.)

In order to check that everything is OK with the generated .dat file for the particular firmware and key pair, have you done a test of the serial DFU using nrfutil as the DFU controller (host)? (Full description in the Secure DFU Bootloader over Serial Link (UART/USB) example documentation.)

You can have a look at the contents of the package with "nrfutil pkg display <name of zip file>", e.g. "nrfutil pkg display my_dfu_package.zip", to check if everything seems to be in order.

For a reference implementation you can have a look at the nrfutil source.

Regards,
Terje

[Erwin v. H.]

Hi,

I made a mistake on my side, the size of the Tx buffer was exact the same size as the expected MTU, I forgot to allocate a byte for the opcode.

Therefore the signature failed everytime after uploading the init packet

Regards,

Erwin