Is it possible to mod the boot code itself to ask for a password that you have saved somewhere, and add a menu option to one of the menus to turn the password on/off or change the password. How dangerous/complex would that be? I'm merely curious.

I think thepenguin7/BrandonW know how to flash custom boot code images, but I wouldn't recommend it unless you really know what you're doing. I think it would be easier and less dangerous if this was an OS mod.

Download the startup app from ti. Then go to here and take your pick from various password programs. Put both of these on your calc. Run the startup app. At the prompt, make sure that the display is set to "on", then select "pgrm" from the type setting. Select "<name>" and push enter. Pick your password program from the list. You're done! NOTE: These instructions are for the TI-83/4+(SE) only. If you don't have one of these calcs, I can't help you.

Thank you. I know how to do this, but this is bypassable and gets shut off during a RAM clear. I'm trying to make it completely intruder-proof as an OS/boot code mod.

Hmm, I don't know then.

I believe that we've only just learned how to do anything with the boot code at all; as far as I know, it's more or less completely read-only. Of course, BrandonW remains the expert, so I look forward to his input.

I would strongly advise against installing this into the boot code. The boot code sets up the calculator, and boots the OS. If it gets screwed up, you have an expensive plastic paperweight.

Patching the OS, however, is another thing. While you can screw the OS up as well, all can be fixed with a transfer of a new OS.

I suggest using zStart, by thepenguin77. It has "run when turned on" and "run on RAM clear" features. (Yes - run on RAM clear! zStart patches the OS to get this to work.) At its current state, there are still some bugs to be worked out, but the program running on startup/RAM clear should be stable.

As mentioned above, go here:
http://www.ticalc.org/pub/83plus/asm/programs/

...and choose a no-stub ASM password protection program. (That is, it does not depend on a shell to run - you run it with Asm(prgmNAMEHERE).) Transfer both the program and the zStart app to your calc. Configure the password protection program (set it up). Then run zStart and install the hooks. Go to the second page of the menu and you will find the options for it. Install the patch, and then exit zStart. Go into your TI-OS programs menu, and find the program you wish to use. Then press...


As indicated above, you *can* use an app (use the same shortcut but in the app menu). However, I haven't tested this yet, so I can't guarantee this works.

Finally, archive the program, and voila - an (almost) foolproof** password protection! Since this is an OS patch, it will survive backup battery removals as well.

Oh, and one last thing. "This" = the patch:


Links:
zStart Project Page
zStart Readme

** There are a few keys that you can press to bypass the program execution, should you forget your password or something goes wrong. However, the people you are guarding against probably won't figure it out unless they happen to read the zStart documentation - highly unlikely. If worst comes to worst, the zStart archive includes the full Z80 ASM source, and you can play around with it to disable certain loopholes, and potentially patch out some other OS features. As always, see the readme for the full scoop.

Reflashing the boot code is a very scary thing. It's only been done a handful of times by people in the community who know what they're doing. We've already bricked one 83+SE by trying to flash BootFree (which we can now safely say DOES NOT work on real hardware).

The boot code patches done so far have involved running arbitrary code when a link cable is inserted or when a certain key is being held down (similar to ON+DEL). We have never patched it in such a way that we replace the normal startup process, which is exactly what you want to do (requiring a password to boot).

Such a change can be done, but unless you know what you're doing, I would really recommend against attempting it...if you mess it up, or even forget the password, you are screwed forever. But since you brought it up, now I'm kind of curious about trying it.

I have made certain boot code patches available (such as running code on one of the spare boot pages or from the extra RAM page if holding down [1], [2], or [3] on boot), but because they contain TI copyrighted code, I can't directly link you to them. But if you look around for them, you can find them.

To directly answer your question, though...you can use Flashy at http://brandonw.net/calcstuff/flashy.zip to reflash the boot code with an image of your choosing. It contains a lot of checks to prevent you from flashing something that can't possibly work, but it's still very easy to make a simple patch and totally break it for good. So again, don't try it unless you're using a pre-made boot image AppVar from somebody, or you really know what you're doing.

Thanks for the input BrandonW. I was merely curious about this in theory. Although, if you would like to try to make something of this nature, I would be interested in trying it.

I think a lot of people would be interested in that sort of thing if you ever got around to playing with it, actually. Of course, I'll be the first to acknowledge that you already have far too many cool projects crowding your plate, though.

He tried this in the last HCWP...needless to say he should have a bricked calculator right now except he got really lucky ...some how

More research needs to be done because the hardware is in such a state of funk at boot that the keypad has issues as well as other things.

Would be nice to have when it is all said and done and working

The last I saw on #ti, BrandonW found that for the TI-83+ he for some reason had to have a jp into some various code rather than a call, which makes very little sense indeed. I'm trying to wrap my brain around what he does was a $90... sled.