@Lost_N_BIOS Is there a way to take a full IDA View-A screenshot??
If not, might as well just give you the pe.bin to take a look.

http://www.mediafire.com/file/2frpvsmnr8ufsw7/pe1.bin/file

CORRECTION= I apologize! Just took a look, and found a folder with some other screenshots... I think the one I posted probably was a "random" one.
Last time I was looking at my bios was 2 years ago. I must return to it so I don't end up embarrassing myself again. Sorry!

Any screenshot program, or windows paint (prt scr, then edit paste into paint)

@Lost_N_BIOS I had no alternative other than take multiple screenshots and place them together... not ideal but works.
This is where the final steps are done, I searched for "53534824h", and found it (at the 12th block). After that, I have no clue what can be done since the example code from Coderush is different.

That's all fine, but where is side by side with the guide, at location you thought was same/similar?

@Lost_N_BIOS I think at the "53534824h" is where the similarities end. When I said "similar", I was mainly referring to everything until that point, where I could get through the steps with no problems. I think the first image I posted was just a point of interest, that I would edit in an attempt to get any result. I was certain that I had to just find out what needs to be edited by testing.
Maybe I'm not expressing this very well...

EDIT: Just followed the method that you posted in the first page (from insanelymac). I couldn't get past step 1 since the bios code is different. There is no "TCPABIOS" in the bios.

And that is why I am optimistic about the Coderush method. The bios is from HP, the code is similar since I got to the last step. I'm just not experienced to determine where I can modify to make the RSA check redundant.
I hope this makes the situation clearer.
In his method, I followed everything until I got to the last step, where he finds the part in the code that need to be edited to get around reboot from failing the rsa check.
At this point any similarities I find are pure stretch/guesses just because I don't really understand what I see, and I don't want to give up.
This is where I need help.
Also, I must have misspoken before, sorry.

I have to see side by side image to have any clue what you are referring to. Yes, might not be exact same of course, but if you want my opinion if it's similar enough to allow same edit possibly, if you are unsure if it's same code area, show me side by side.

If you think it's similar enough for coderush guide to be same thing, show me side by side and I can advise you how to bypass (Show me what you want bypassed, and make note beside it in the flow chart, what it's hex values are)
I don't know a lot about coding/assembly, but I do know how to bypass areas, skip something, or change jumps in many different ways

@Lost_N_BIOS Hope this helps a bit.
In regards to hex, what exactly do you want to see?

For any single line in IDA flow view, if you switch to hex view tab that command is highlighted in hex (This hex, I meant you copy/paste into image at the flow chart location where you for example wanted some jump changed or bypassed)

Thanks, I see now, it's not same at all, you do not even have any "test" below your searched item, only a few compares, but none similar enough to his example, and none would skip to end by changing instructions either.
He'd have to look at that himself, and maybe advise you, I'm not familiar enough with assembly to know if anything is possible that would fix this for you there like in his article or not.
If he's not too busy, maybe he will stop in and advise

@CodeRush - If/when you have time, could you check above image and see if/where he can edit to bypass per your guide here - https://habr.com/en/post/249939/
Thanks

@Lost_N_BIOS Got it!
Well, I kept looking to see if there anything remotely similar, -remembering I don't have much clue of what needs to be done at this point- and there is a block, the 10th from bottom to top, that jumps to a "xor, eax eax" and goes to the 3 blocks that are equivalent to the last one from Coderush. It is also right after the 100h reference just like in Coderush's example.
Question is: Can a forced jump (jnz -> jmp) do anything in this case?


Also, thank you for asking for his help

You need to make sure that EAX has 0 in it, and then perform a proper return from this function. Replacing that JNZ to JMP is a suitable way to do it.
However, in you code there's no dead-loop that we are trying to not fall into (it's probably in the function that calls this one now), so the only thing that your patch will be doing is "make any address it gets as a candidate for signature location to say signature is there", which is probably not what you really want here.

@CodeRush Thank you for the info. Can you point exactly what needs to be changed into what? Or can you take a look at the pe.bin itself? If this is not too much to ask of you.
http://www.mediafire.com/file/2frpvsmnr8ufsw7/pe1.bin/file

This is where the system hangs on invalid signature:


This is where and how to patch it:

Sorry, one picture got broken, so I removed it.
Basically, we need to return success from the function with the dead loop (not just the one that locates the signature). Previously everything were in a single one, and that's what got you confused.
The easiest way out from this function is that JNZ, that takes us either to the main body of the function (on TRUE edge) where the signature search and verification eventually happens, or (on FALSE edge) to "return EFI_SUCCESS" (xor eax, eax, ..., ret). The patch then is to make sure that TRUE edge can't ever happen, which is just to skip the whole JNZ and always take "xor eax, eax, ..., ret" route instead. Patch is therefore "replace JNZ with NOPs", 75xx->9090.

@CodeRush Perfect!! I will be able to test it next couple of days.

Thank you very much!!

@CodeRush @Kirfve I've been following this thread for some time and I have a question for you. Do you need to access the BIOS currently installed via a CH341A to edit, or can I work on a copy of BIOS downloaded on HP website? From what I've read, I understand that you @Kirfve work on the one you get via CH341A, am I correct?

Would I also be able to flash a modded BIOS without CH341A, if I manage to work it all out? I have a HP 15-bw0xx, same BIOS as OP's.