Matt Reed-
I have see similar things done about notes. One time my teacher saw some girls in my class passing notes. He stopped them, took the note, read it to the class, recorded it on a tape reocrder, gave the note back to the girls, called the principal in, and played the tape to him. Just to embarass the girls. It took the whole class time for this. I have seen other things done. Many teachers use embarassment as a means of punishment....and many will go to EXTREAMES to embarass the "note passers."

(Did I spell extreams right?)

No.

It's spelled "extremes"

Sorry if this is a superfluous message.

I think both the encryption and the compressor would be very useful. As for using it for note passing, this would be really cool! I don't pass notes myself, but I would start just to use the encryption. What I do to pass notes electronically on the calc is save the message on the E2 and give it to someone to give to my friend recieving it. Since everyone in my school has 85s, this is a big problem for intercepting messages. I pretty much solved my problem with my encryption program(uses the most advanced algorithm I have seen for the calc). As of yet, no one has been able to crack it. This was written in basic so just imagine the potential of an ASM version! I also think the compressor is very useful too. I also wrote one of the above types(convert to string) but it didn't work out(my calc crashed and I didn't feel like redoing it). I think it would be easy to do. Just port some compressor for the Z80 from the '80s to Usgard or something. I'm shure by now that source code should be available.

I would very much appreciate it if you would E-mail me with an English (no TI-Basic source code please) description of your encryption program. I hold that every programmer fancies himself a cryptographer, and if they have not had formal training, then, without exception, they will suck. No offense. I made a Simultaneous OTP program for the 85 a while back... I now realize that it was probably breakable.
Also please don't say "most advanced algorithm". If it is your own homemade thing, it frankly, sucks. Sorry, but you're not a cryptographer. And neither am I - that's why I'm implementing a well-known algorithm.

Not to be rude or anything, but I think this statement:

>Also please don't say "most advanced algorithm". If it is your own homemade thing, it frankly, sucks. Sorry, but you're not a cryptographer.<

isn't necessary. Just because a person did their own encryption program doesn't mean it sucks. I'm sure you know that there are some people out there that can do things better than some trained professional can do. Why don't you try encouraging people? This person might be the one who makes this encryption program you want.

You see, I frequent the USENET newsgroup sci.crypt, and I've learned a few things. First of all, cryptology is a very mathematical business, and also very difficult. Second of all, there is a LONG history of average joe's algorithms being used in commercial products, and then cracked wide open. The only algorithms that withstand the test of time are those made by experienced cryptanalysts, and even then, most of them get cracked. I'd like to see if any average joe's algorithm could resist linear or differential cryptanalysis, known-plaintext attacks, etc. There are SURPRISINGLY few encryption algorithms that are still good today. I, for the life of me, cannot think of even ONE of them that was designed by an average joe.

Who is going to attack the crypto on the calculator with things like known-plaintext attacks? We are still talking about a calculator, and this idea began with passing notes. No one said at the beginning that we were going to try to make this good enough to be industrially used! I'm sorry if I insulted you, but don't get so uptight!
And This is a first time post at 4:02 A.M. by chris Schmidt

I would be one of those people. Just to see what fellow students are saying :)

Actually, about algorithms only being written by professionals, YOU'RE
WRONG!!!

RSA was written by three inexperienced people, yet became one of the most
famous algorithms. Yes, most programmers' encryption programs SUCK. But not
always.

BYW, everyone should use PGP.

I didn't use it on this msg cuz it won't take words over 50 chars, and I was to lazy to change the word wrap thing.

RSA was NOT developed by three "inexperienced people". Quite the opposite: It was developed by three MIT computer science researchers who were the first people outside of a government agency to develop a reversible one-way function and realize the applications to the field of cryptography.

This could potentially be the best damned thing to happen to a calc. The possibility of increasing your mem from 1.5x to 2x is astounding and should be implemented ASAP. But what would be even better would be a password program that uses 384 bit encryption. Imagine a program that if the wrong password is entered, would encrypt every damned thing on your calc, so that the only thing you could do is turn it off, and then back on again, to get the password prompt. This would be extremely usefull for those of us who are sick of not being able to use a Ti-92 in school because of the mob of idiots who want to play games, and will grab the calc out of your backpack to do so. Also, compression would be extremely useful for those of us who like to read in class, yet hate to carry huge books (like The Wheel of Time), imagine reading a full sized book on your calc in math when your (idiot?) teacher thinks your doing a math problem. Aside from these few thoughts I have to offer, the possibilities are endless...

I completely agree with you. Though my school is a tad more sane than yours, apparently. I, frankly, have neither the skills nor the time to make a GPC. Though it is a damned good idea. I do have the skills and time to make calculator encryption. With a new modification I realized while reading these boards, anything could potentially be encrypted with an 8-character password. Thus no one without your secret key on your calc would have access to the encrypted stuff, and even with the calc, they must brute-force the 8-character password.
The book "FlatLand" has no copyright on it any more, it is over 100 years old. I have a copy of it on my computer. When I get the time, I will break it into 40K chunks and make them into TI-92 Text Editor files, probably 5 or 6 in total. This way, a normal TI-92er could read 1 part a day (load a new one from your computer the next day) and a TI-92+er coould read the whole darn thing. :-D

About encyrption: If the teacher doesn't even know the encryption technique, it doesn't matter how simple it is...

About compression: I have a ti83. If the compression proggie will give me 2x, this will add 27k or so... The problem is that it probably will only add 1.5x (14k) and the compress/decompress programs will have to be on my calc...

If the compress program is more than 10k, Its not worth it. (dont' forget to leave space to run the uncompressed program!)

-- Justin

it's only not useful on an 82, 83, or 85 if it's over 10k (which it probably would be)



keep in mind there is the 86, 89, 92, and 92+, all of which would gain more than 50k by a compression program which would only take up around 10k itself.



please think of others rather than just yourself. the ti-83 is not the _only_ calculator.

Yes, I agree. Other calculators than the TI-83 exist. The 83 isn't that good, anyway. Follows are my opinions on the TI calculators. Please note two things:
1) These are MY opinions. They are just here so you can know what I think.
2) Please do not respond to this post. I do not desire nor want a TI calcuator argument to spring up.

TI-73: Middle school, *gag*. I hope assembly shells are never made for it. Geez, I went through Algebra I with a TI-30, anyone else can too. Assembly shells would mean games, and considering the sorry state of middle schools, that means the decline of math and the rise of games.
TI-80: This calculator is simply too weak. It is not desirable for any higher math.
TI-82 and TI-83: Undesirable. They are too weak, and too close in price to the 85. They are used by high school students taking Algebra. *sigh* Algebra should be taught in middle school.
TI-85: Finally, a calculator that deserves respect. It can be used for Calculus classes, and is very powerful. There is a disturbing amount of games for it, though.
TI-86: A calculator, that, while more powerful than the TI-85, deserves less respect in my opinion. Too many people play games on it, I have seen.
TI-89: A stripped-down TI-92+ with a smaller screen and no geometry. This is less desirable than the TI-92+. Besides, no one needs this thing on the SAT. I got a 1600 with a TI-85 with 1K of free memory.
TI-92: A VERY good calculator, and large screen also. Not to mention that it has very few games for it.
TI-92+: This is the best. A TI-92+ deserves respect. And few to no games. :-D

As you can tell, I don't like games that much. The only - ONLY - game I retain on my TI-85 is the Insane Game. I discovered it a while back, while it was in an early version, and I believe it's worthwhile to keep on my calc.
As I said before, these are my opinions. Disagree or agree with them as you may. But let's not start a "Which TI is better" feud.

*This is not meant as a which calc is better post*

I know over 20 people who used an 82/83 on the AP Calc test and managed to get a 5 on it, so they are not only meant for middle school algebra.

As for your feelings about the 86, it has some very decent math programs for it, such as the asaps and stuff that add more trig functions like sec,csc,cot and so on. Just because some people play games on it doesn't mean it isn't a good calculator.

>TI-82 and TI-83: Undesirable. They are too weak, and too close in price to the 85. They are used by high school students taking Algebra. *sigh* Algebra should be taught in middle school.

The TI-82 is weak, however, the TI-83 is quite adequate for all your computing needs. I know many people including myself who took Algebra in middle school, and take more advanced course (PreCalculus onwards) with their beloved TI-83.

>TI-85: Finally, a calculator that deserves respect. It can be used for Calculus classes, and is very powerful. There is a disturbing amount of games for it, though.

The TI-85 is an impotent waste of silicon... When compared to more recent developments. Trying to port programs from the 83 to the 85 is impossible, due to a lack of a function that will (quickly) search a string for a subset, starting from a character. This problem also plagues the 86.

This is in the rudimentary programming language inherent within the system, of course.

>*sigh* Algebra should be taught in middle school.

Last time I checked (which was Friday) Algebra was taught in middle school, I take it :P

BTW off that response

I hate people who will steal my calc out of my pocket, backpack, binder, etc. the only way to keep them off is to clear the memory and tell them I had a math test and the teacher made me clear it. Whoever suggested a program that encrypts everything if the wrong pw is entered had a good idea.

There are already programs (at least for the 86) which will put a password on the calc, and refuse to start up if you don't type it in correctly. ASE, an assembley shell, does this. Also, I use matrix encryption with a program I wrote, but it's so simple to crack (of course, i wrote it, so it wasn't too hard to figure out a way to bypass it). (It is a one-way encryption, but if you fill the result matrix, and the encryption matrix (filled with random #s when the program is installed) with zeros, it thinks that any password you type is the correct one.

Like the original author of the message said, even if you think your encryption scheme is great, it can be cracked, if you're not a professional. And it's probably simpler to do than you think.

However, no average high-schooler or teacher will know a thing about how the encryption program works, and they won't want to bother trying to crack it either. So it really doesn't matter how weak the encryption scheme is, as long as it's fast. The method I'm using now (the second one i made) gets the password you type from a getkey loop (in basic) and then just one-way encrypts that, and compares it to the encrypted real password (which is why if you set the encrypted password matrix to all zeros and the translation matrix to all zeros, the encryption is useless. It uses matrix multiplication, so anything you type turns into a matrix of zeros.)

Sorry if I rambled. The point is, even crackable encryption methods are fine, if nobody is going to bother to take the time to try to crack them.

Rich D.

I personally own an 83, and I think it is a very capable calculator. People seem to think it is a weak calculator with few features, but that is not the case. I can only think of one thing that I would change about it, the memory. Sometimes it is a little small. But otherwise, it is good, and I would not trade it for an 85 or 86 for the world. As for the 89, 92, and 92+, I'm in high school and I don't need that kind of brute force. I'm a pretty decent programmer in Basic and I've done some nice things with my 83.

Over 10k?!?!
do you know anything about compression, or asm programming? Take a look at Lempel-Ziv. A program using this kind of algorithm would not be larger than 1k.

I am presently cracking a fairly simple keyless encryption program for the TI-89 called imcode(), which is set where you can't edit it. I am almost finished solving it, and I haven't seen the actual program once.