SAMSUNG YH-920

[Bagder]

"The build" being what build? You mean the output from a Rockbox H10 bootloader build?

Did you then decrypt that and re-encrypt it with the YH920 key?

You may need to pay some attention to these facts:

#1 - the only YH920 mi4 file I've dissected used the older and smaller mi4 header so you may need to do that too (with "mi4code build -2")

#2 - the YH920 has a minor difference in the mi4 file mentioned on the mi4 file format page that might have significance (or not). It has not been that thoroughly investigated since you're about the first one trying anything on such a device!

[pyro_maniac]

"The build" being what build? You mean the output from a Rockbox H10 bootloader build?

Oh yes sorry. I took the rockbox.mi4 file that comes out of the H10 build.

Did you then decrypt that and re-encrypt it with the YH920 key?

No but i will do so later.

/EDIT: The key is always the same. It takes always the default key.

Code: [Select]

mi4code decrypt rockbox.mi4 rockbox-enc.mi4
mi4code v1.1.2-DSA (c) by MrH 2008
Secondary label end offset 'default' (0xec)
Decrypted ok with key 'default' (20d36cc0 10e8c07d c0e7dcaa 107eb080)
Is that the right way or is there a misstake in my acting?

#1 - the only YH920 mi4 file I've dissected used the older and smaller mi4 header so you may need to do that too (with "mi4code build -2")

Ok that later, too. I will post all results of that.

/EDIT: What should i do with that header?

#2 - the YH920 has a minor difference in the mi4 file mentioned on the mi4 file format page that might have significance (or not). It has not been that thoroughly investigated since you're about the first one trying anything on such a device!

That looked different to me because i've found some posts here, so i thought there were some other tryings. Maybe with your help i can get a running version. I really like to learn it.  

[Bagder]

Maybe with your help i can get a running version.

I'm only helping you trying to get the H10 version adapted to get accepted by the YH920.

There's really only a very very slim chance that it'll actually show or do anything on the target as I doubt they are that identical hw-wise.

[pyro_maniac]

Is there any possibility to raise the chance?

[Bagder]

Is there any possibility to raise the chance?

As you must've seen on the NewPort wiki page, the taking apart, scanning pcb and identifying hw steps are all prior to writing a bootloader...

[pyro_maniac]

Yes i ve read that wiki. I thought that scanning the pcb is through. I m not that good in reverse engineering but i will try to learn it. Are there any hints for getting started at reversing the firmware?

Should i stop modifying the firmware to get it load at the original bootloader?

What should i do with the header that i generated with mi4code build -2?

[Bagder]

What should i do with the header that i generated with mi4code build -2?

You can use "mi4code build -2" to create an mi4 file with the old smaller header that the original yh920 file we've seen has.

[pyro_maniac]

i am confused. What are the next steps?

Should i move on in modifying the mi4 file or should i try to reverse it?

[Bagder]

i am confused. What are the next steps?

Should i move on in modifying the mi4 file or should i try to reverse it?

If you want to try the h10 mi4 file on your yh920 you can try the mi4code trick. That  has a very small chance of doing anything fun.

If you want to actually make Rockbox progress towards a true port for the yh920 then you follow the NewPort wiki page steps.

[pyro_maniac]

Ok then i will try to help porting it. I will try to reverse the firmware but i am not very good at it. Or are there other jobs left? The wiki looks very far.

[Bagder]

You are the first and only person showing interest in this device. Thus all jobs are yours...

[pyro_maniac]

Oh.... that sounds tricky.
But there are so many informations in the wiki. Pictures of the PCB and so on!? That work is done already or have i do remake it?
My options are limited by my know how.

Are there any hints from other mi4 reverse engeneerings? I ve never done something like that befor.

[Bagder]

There's no need to redo what's already done, no.

And for reverse engineering you need to learn how to disassemble the decrypted mi4 file and then read and understand the output. It is ARM code.

That might require more than just an afternoon or two.

[pyro_maniac]

I will try it. I work in a company that is developing a arm handy so maybe i can  get some help here.

But that looks like a really big work for me. I am surprised that nobody else is working on that because i m not the first naming that device,

/EDIT: I could not find the bootloader. It seems to be on an extra flash or something like that.

[pyro_maniac]

I ve made an objdump but i m not good in assembler! Should i post it or what should i do?