Re: A83: Patching the Ti83+ ROM?


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Re: A83: Patching the Ti83+ ROM?




At 19:26 2001-01-27, you wrote:

>Yeah, it's possible to edit the OS file in a hex editor before sending it to
>a calculator.  The problem is that the calculator wont accept the file
>afterwards :)  It uses a complicated validation scheme that you can feel
>free to try to crack, but I don't think you'll have any success.
>
>-Dan Englender

No, trying to crack the validation scheme and generating new checksums and 
such is probably that hard that it is virtually impossible.
Much smarter to try to go "the other way around" and try to find loopholes 
in the OS on the calc.
(The calc IS writing at some point to its own flash...)
On the ti89, such loopholes have been found on almost every AMS (the OS) 
version, and now there is one that works on all AMS versions, all 
HW-versions (there is 2 version of the hardware of the ti89 out there), but 
it is kept secret. (no, I don't know it)
I don't know anything about how the protection in the 83+ is implemented 
though, so I can't say anything about where to look or something like that.

///Olle




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