Checksum calculation?
 

Hi!

Can anybody tell me how the checksums are calculated?

If MCU or PPM is changed, but the checksums are the same does the phone still need logging for FAID?

I was just told you can "reflash" the same mcu and ppm (HAS TO BE THE SAME LANG. PACK!) and you don't need to recalc.. I done it today!<br />Didn't fix my problem tho <img src="frown.gif" border="0">

The checksums WONT be the same if you change mcu or ppm thought, thats the problem.

The FAID is calculated FROM the checksums and MSID I think.

Nick

The bytes can be modified and the checksums can still be the same. For example if you calculate the checksum by adding the bytes and discarding the carry then if you have 13 54 21 it will give the same checksum as 15 53 20. So in theory you can modify the MCU or PPM and then fix a word somwhere where is not needed and adjust the checksums to be the same.

So if the checksums are adjusted in this way will the phone work without logging?

What exactly is the MSID? Is it calculated from smth? Where from?

Mircea

P.S. Sorry for the double posting.

Bear in mind that the phone itself also checks the word (2-bytes) every 20h of the flash.

You are right that the checksums of 13 54 21 and 15 53 20 are the same but let's say "13 54" happens to be in one of every 20h of the flash.

So the changed "15 23" would cause a no network and phone resetting if not for the ever famous "Contact Service".

So the idea is to keep the checksums the same and also the n*20h,n*21h bytes the same in order to avoid logging, or is it enough just to keep the 20h,21h bytes the same?

Where is this 20-21 checksum calculated? In hardware?

Isn't this checksum also additive? What will happen if this 20-21 checksum is also adjusted like I said before? Will the phone still need logging? Is anyone brave enough to try? I don't have flasher cable yet, otherwise I would try it myself.

give me more info and I will try... mail me

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