How to prevent a program on TI-84 from being transferred to another calculator?

Question

I am trying to allow others to use my programs, but I don't want those users to be sharing the programs without my permission, so my goal is to prevent the users from doing this on the TI-84 calculator, but I have had no apparent luck.

For the TI-84 calculator, I have tried the getkey command and the stop. I have tried conditional statements with for and while loops, but I can't seem to prevent the user from sharing the code.

Prompt V
V+2 -> C
Disp C

The code works like it is intended but I can't prevent people from transferring this code to other calculators.

Answer 1

There is no way to prevent people from transferring programs over the calculator. What you could try to do is make it so that after you transfer the program yourself you store a password into a variable that they are unlikely to use (done manually, make sure to clear afterwards). When the program runs it checks if the variable stores the correct value. If someone else transfers the program and doesn't load the password into the correct variable, then the program won't work. However, they can figure this out by simply reading the code. If you want to be extra tricky, you can create a simple hashing algorithm and read from multiple variables. For instance, storing 123 in Z could be hashed by *28 + 54 mod 71 to get to 19. Apply those math functions to the chosen variables and then compare to their hashed value. This protects people from figuring out the password by checking the program (since 19 cannot be reversed to 123). Of course, they can just delete the check, so try to hide it somewhere among junk code. Now, they might overwrite those variables where your password is stored (often by running other programs that use those variables). Simply tell them that they have to come back to you so you can "fix" their program. Hope this helps.