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  #21  
Old 02-18-2006, 02:36 PM
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I also thought about that. But unless I know how they create the checksum, I cannot reproduce it.
The most simple would be XOR but there is also CRC etc.

I guess without further inside info we are screwed or can just try.
My program replaces the images very exactly. So if someone can exchange the image with a smaller one (filesize) and it works, then we know that there is no checksum.
With bigger file is always the risk to "disturb" the bytes of the next file.

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  #22  
Old 02-18-2006, 02:54 PM
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Quote:
Originally Posted by 2Wires
So if someone can exchange the image with a smaller one (filesize) and it works, then we know that there is no checksum.
In my experiments, I tried to change 7 bytes in the logo part of navboot (just for testing checksum existance). After that Paint opened the logo (copied from navboot), but navi writes about error during update. I think, checksum control exists.
  #23  
Old 02-18-2006, 03:18 PM
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@DaRkY
Which bytes did you change? Did you check if the image was still valid?
Paint opened it but that doesn't anything since it might repair the file.
Best way would be to replace it with a smaller valid file.

I uploaded an altered navboot here:
www.carmes.de/download/software/navboot
Maybe someone can try that.

Tino

Last edited by 2Wires; 02-18-2006 at 03:28 PM.
  #24  
Old 02-18-2006, 03:30 PM
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Quote:
Originally Posted by navman
So far instance if the first byte of the spare 5Kb of data is a 0, then if you change it to a 255, then your 255 nearer to the correct checksum..keep doing this over the 5Kb of data until the original checksum for the 30kb is reached..NavMan
I think, that checksum calculating is not so easy For example, checksum of 1 FF byte file is 3045181057, and checksum of 1 FE byte file is 1738016605.
  #25  
Old 02-18-2006, 03:35 PM
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If we know where the checksum is and how it is calculated. We just calculate it for the altered navboot.
But that need more inside information or luck finding it
  #26  
Old 02-18-2006, 03:41 PM
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I have the same issue, how did you solve it? thanks

Quote:
Originally Posted by Scottie
thanks for that never burned a disk in my life so will need to buy some cd's tomorrow. don't even know if it will allow me to burn using my Laptop.

I've downloaded the alcohol 120% and the files. However when I pick the v26-09a then click next it comes up with this message:

Because an unsupported image fiel format is being used,you should manually set the track format,block size and other information. You MUST do this to record the image file!

NOTE: The unsupported image file will be burned/emulated as a ONE-track_only disc. If this image file contains multi-track data,the burned/emulated disc will not be recorded the same as the original disc.

What should I do next???? HELP!!!
  #27  
Old 02-18-2006, 03:47 PM
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Why dont we extract the original BMW image used on the MK IV navs and see if that works... and then go from there
  #28  
Old 02-18-2006, 03:53 PM
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Quote:
Originally Posted by 2Wires
Which bytes did you change? Did you check if the image was still valid?
Bytes was in the centre of gif. I'll chek it with Paint. It is sensitive to the file format. It did not open edited files, that other progs opened.
Quote:
Originally Posted by 2Wires
Paint opened it but that doesn't anything since it might repair the file.
Best way would be to replace it with a smaller valid file.
Diferense between files I must fill with 00?

Quote:
Originally Posted by 2Wires
I uploaded an altered navboot here:
www.carmes.de/download/software/navboot
Maybe someone can try that.
I can do it only tomorrow

Quote:
Originally Posted by 2Wires
If we know where the checksum is and how it is calculated. We just calculate it for the altered navboot.
But that need more inside information or luck finding it
I thought, that checksum calculating method is the same for all files. I'm a newbie in it.
  #29  
Old 02-18-2006, 04:03 PM
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Quote:
Originally Posted by DaRkY
Diferense between files I must fill with 00?
Yes. But my program does it automatically when you insert a smaller image.

Quote:
Originally Posted by DaRkY
I thought, that checksum calculating method is the same for all files. I'm a newbie in it.
No, there are many ways. CRC32 is the most common and quite safe.
XOR is very easy and just used for smaller codes like the IBus/KBus communication.
  #30  
Old 02-18-2006, 04:20 PM
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Paul- I along with everyone else here applaud your efforts and your methods!

JV
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What gets us into trouble is not what we don't know...it's what we know for sure that just ain't so
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