Author Topic: Downgrade your TI-84 without reflashing the Boot Code  (Read 12424 times)

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Offline critor

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Downgrade your TI-84 without reflashing the Boot Code
« on: May 28, 2012, 11:40:34 am »
Summer 2009, the TI community factored all 512-bits RSA keys used to validate OS and Apps installation on TI-z80 and TI-68k Flash calculators.

This opened the way to:
  • patched OSes and Apps
  • 3rd party OSes and Apps



Some of the patches disabled the TI-84 PTT mode, and TI must have been bothered with that.

Spring 2011, we discovered a new 1.03 Boot Code on the new TI-84 Pocket and on TI-84 Plus hardware revision Q and above.



That new Boot Code adds a 2nd validation check for the OS installation with a 2048-bits RSA key only included in OS 2.55MP.

So you had to:
  • wait 6 additional minutes at the "Validating..." screen after sending an OS
  • stay with the lastest 2.55MP OS which breaks compatibility with several asm games




Then, Brandon Wilson discovered a way to reflash the TI-84 Boot Code. You could then downgrade your Boot Code to 1.02 or 1.00 and then downgrade the OS. ;D
But you had to get such Boot Code image, which is different between basic and Silver Edition TI-84.




Brandon then released EpicFail, a Boot Code 1.03 patch. No need to dump the Boot Code on a model you don't own anymore.
But you might break your TI-84 permanently if anything bad happends during the Boot Code flashing, and using such tools might void your warranty from TI point of view.



Brandon then worked on a 3rd way: a patched TI-84 2.43 OS which can be installed on Boot Code 1.03 because of some exploits. But it could not be shared publicly because of copyright reasons...

On TI-Planet we just converted that into a dynamic patch for every TI-84 OS; Make103!  ;D

You can now make every TI-84 0.46 to 2.53MP OS installable on your original Boot Code 1.03! ;D
It also works with TI-83 Plus OSes patched to be installed on the TI-84.
For now it doesn't work with 3rd-party OSes which are much smaller and don't reach the 2048-bits RSA key location (and so exploit) in ROM.



Download from the TI-Planet news:
http://tiplanet.org/forum/viewtopic.php?t=9333
« Last Edit: May 28, 2012, 11:51:19 am by critor »
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Offline thepenguin77

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Re: Downgrade your TI-84 withour reflashing the Boot Code
« Reply #1 on: May 28, 2012, 11:43:54 am »
If you want to do 3rd party OS's, or any OS for that matter, don't forget unsigned. It lets you send unsigned OS's to your calculator.
« Last Edit: May 28, 2012, 11:44:23 am by thepenguin77 »
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Offline critor

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Re: Downgrade your TI-84 withour reflashing the Boot Code
« Reply #2 on: May 28, 2012, 11:52:48 am »
Oh sorry, I missed it.

Seems we made similar patches. :)
« Last Edit: May 28, 2012, 11:52:59 am by critor »
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Offline thepenguin77

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Re: Downgrade your TI-84 without reflashing the Boot Code
« Reply #3 on: May 28, 2012, 12:30:13 pm »
Actually, mine is very different. It mods the certificate.

The difference is that the brandonW version is specific to the OS while mine is specific to the calculator.
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Offline apcalc

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Re: Downgrade your TI-84 without reflashing the Boot Code
« Reply #4 on: May 28, 2012, 01:40:07 pm »
Very nice!  Great pics and work! ;)


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Re: Downgrade your TI-84 without reflashing the Boot Code
« Reply #5 on: May 28, 2012, 03:40:11 pm »
Good stuff Critor :)

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Re: Downgrade your TI-84 without reflashing the Boot Code
« Reply #6 on: May 28, 2012, 06:53:47 pm »
Hey that's great :D

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Re: Downgrade your TI-84 without reflashing the Boot Code
« Reply #7 on: May 29, 2012, 04:09:52 pm »
By the way, there was a 0.46?
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