I can't run your program:( It writes, that there is an error during initialization (0xc0000135). Maybe I don't have some library?

I don't know, how this calculating works.
Is there any possibility to make a logo, that have an equal checksum with the original logo? Or there are no deal in this, because checksum of navboot changes even if we paste a gif with right checksum?

Great stuff with this gif-extractor! But why doesn't it extract the MINI-Logo?

I think it has somethiing to do with checksum. May be have to edit the file that reads the checksum for the new checksum. :dunno:
Thanks Paul for your efforts. :bow:

@Darky
Please load the newest version of my program and be sure .NET Framework 1.1 is installed.

Just replacing the image with the same image won't change the checksum since no byte changes.
But unless we know which method is used to calculate the checksum we can't do anything.

Sorry yes, I should have realised, that if the checksum is calculated by XORing, then my idea of just altering the spare space after the replacement GIF data won't work.. we would need inside info for that..

Can someone do a test... Alter one byte in the original GIF, and add one to it, then take another byte from the original GIF, and subtract one from it.. If when burnt to disc, the update goes OK, the the checksum is a simple totaling of the bytes in the file, and therefore my original idea could be used..

NavMan

It's almost certain that there will be some sort of checksum on the data uploaded to the nav computer. It's very likly that this will be written at the end of one of the files. The best way of finding this would be to try and work out the checksum on the origional unaltered file in various ways and see if you can find a match for that value. Once you know how to calculate the check sum and where it is, the rest should be easy! :)

It appears that Tino's CarMES points to a different GIF (00B438C8) than the one I was modifying at 00B1FE84-00B21D8F. Let me see if modifying this one instead makes a difference.

Wow... it's almost half the size of the file I have been working on.

OK...

I've used Tino's excellent application (see his post in the other thread - http://www.xoutpost.com/101854-post105.html)

...and I've noticed that there are TWO identical splash screens embedded within the NAVBOOT file - maybe the checksum is as simple as having inserted two identical images??

One at B1FE84-B21044
One at B438C8-B44A88

Both have lengths of 4544 (HEX length = 11C0)

I'll try this out later today (unless someone beats me to it!)

Is it possible to bring splash screen discussion to this thread so it is all in one place?

Paul Martin
Australia

Good Work RealShakaZulu, I've found this too - and GREAT WORK Tino! Makes extraction easier!

See my post in this thread (Splash Screen - http://www.xoutpost.com/navigation-sy...sh-screen.html)

What if we just make sure that BOTH images are the same? Maybe the checksum is nothing more than making sure both images are identical?

Could we move Splash Screen discussion to the other thread to keep the topics organised? What do you think? (SEEMS TO HAVE BEEN DONE! THANKS :D)

Paul Martin
Australia