PICTOCRYP v0.5B For The TI-83 Plus

Comments/questions/bugs to wallbangicus@hotmail.com

Pictocrypt is a picture cryptography program.

Start out running PICTOCRY

When you first run the program, you will be told to let the datagen subroutine run: do so. This writes a bunch of random garbage data to the graph screen. Although it isn't nessisary, its recommended you do so. The random data is an extra security precaution to help make any form of mathamatical decryption impossible. If you don't have the patience to wait it out, you can simply hit [ON] and rerun the program to bypass it.

The second step would be to generate a keycode. To do this, from the main menu, scroll down to "4:KEYGEN" and press enter. Now enter any number, but make sure you remember it. The program will now ask you for a password: enter it and remember it. You should see a jumbled up form of the word. The calculator, and every other electronic computing device, uses pseudo-random number generators. Numbers are made using something refered to as a "seed" and the number you entered before the password is it. The random number generator works on a mathamatic principal, and math is so accurate it can't truly be random, everything must always follow a pattern. So in decrypting the message, as long as the same number is provided, the random numbers generated will always be the same. So in other words, the password is mixed up using this random-pattern. No pun intended.

You should now be returned to the main screen. 

Goto "2:ENCODE"

You can encode an already entered message that is in Str1 by going to "1:STR1", or typing a new message by going to "2:TEXT". After you make your selection, You should see a loading screen. Just wait patiently for the program to compute. Once 100% is reached, you will see your random data that you generated earlier with little bits and pieces changing. The amount it changes depends on how long the message is. It is imperative you don't hit [ON] at this point. the data is already encrypted, its just saving it to the picture. If you do, it leaves all sorts of data some autistic kid (or maybe your math teacher) could use to very easily decode your message.

A little prompt should pop up now asking which picture to store the encrypted data to: enter a number 1-9. Each number coresponds to the picture with the same number. So if you wrote a message to Susan, and gave the number 3 at the prompt, you would then send "Pic3" to Susan's calculator and tell her the number and the password to decrypt the message.

So now you have a encrypted message. That doesn't do you much good if you can't read it. So, to decrypt it, 
hit [2ND] [PRGM] [<] [2] then the number the picture was saved to. So if this was Susan's message from the example above, it would be 3. Then goto "4:KEYGEN" again and type in the random number and the password the message was encrypted with. It will return you to the main menu when its finished. Now goto Decode, wait for the percentage to reach 100%, and read the decrypted message.

The only bug I know of and am too lazy to track down, is if the character in the 16th or any multiple of the 16th position has a value higher than or equal to 32, it will subtract 32 from its character value. So in English, theres a very small chance of a message being one, and very rarely two, characters off.

I hope the guide was helpful. Feel free to contact me with any ideas/bugs/comments/suggestions with my email address at the top of this document.