TEA Encryption

[rastan]

lol, yeah. dont know where that came from actually, possibly english, possibly more local. dont know

phil

[Dwayne]

Hello Rastan,

Rastan, in c/c++ I use a encryption code as a word. In Assembly (or with Micochips) it lacks the ability do do such, except without high overhead and usage of memory.

One of the oldest tricks in the book, is substitute a letter for a letter (just like a cryptocrypt in the newspaper. If you can give the reader the code to decipher it, then it is easy to "crack".

Now, lets make this one step easier yet...99.9999 percent of all code crackers give up pretty easily. If you get that .00001 percent person, you are just out of luck. (That is why they have EUA that say you cannot "reverse engineer" etc etc etc). (Who would want to reverse Engineer a 100 meg program?) Though I have to admit, I spent 2 months reverse engineering a program and cracking it, because it used a lazer spot on a disk for its security. The company wanted BIG bucks for a upgrade, and all I wanted to do, was to get our companies data off of their file structure into "FAT"/"DOS" TEXT format, to do our own programming and Information Technology. The week I finally got our info off their "format", was the week we trashed their thousands of dollars of programs, their thousands of dollar upgrades, and said "Good Bye". the system was called NIAWKA. I think they are still in business too. They had software that took the old WANG 2200 systems, created a special "Platter" on FAT disks, and made IBM machines think they are WANG 2200 machines. It worked very well. But I wanted to be fully DOS/FAT without anyones "imulator"

Now with that said, to do a cheapy for the spoof of the 99.9999 people...
two ways how you can do it.
1.

a=g
b=f
c=j
d=d
...
...

doing it this way, you will need a table with 255 table for a lookup. and you need to pass that table to the reader, to "reverse engineer" and make sense out of it.

The other way, is to add a certain "number" to your table... Lets say we pick the number "5"

1=1+5=6
2=7
3=8
.....
251=0
252=1
255=5

(notice when you went above 255, it started back to zero. Sine the highest number the variable can read is 255, it automatically rolls over for you! To "reverse engineer" it you just subtract 5.

"Hello World" with just "1" added to the hex value looks like this:
Ifmmp#Xpsme

For most people, that looks like garbage...At worse case senario, they will find the code in 254 tries

the code would like something like this:

Sentence ="Hello World"
code number var 1
for counter=1 to sentencelength.
Sentence[counter]=sentence[counter]+1;
next counter


Dwayne

[rastan]

ok good idea dwayne. ill give it a go.

thanks,

phil

[Dwayne]

Hello Rastan,

One other thing...(explaining the code word);
IN these pic chips, you pass a number (my last example uses the value 1).

Sometimes you may want to pass a code word.

What you can do, is a kind of CRC on that word, and pass THAT number.

Example:
CodeWord ="SecretWord"
PassingValue var byte;

PassingValue=0;
For counter=1 to CodeWordLength
PassingValue=PassingValue+CodeWord[counter]
Next counter

What this does, is add up each individual character in CodeWord.
if it goes above 255, it automatically rolls over to zero and starts over
again. When you get done adding up your characters out of your SecretWord, you will have a number (CRC) between 0 and 255.

Another (more complicated to some degree, but just as easy), is to
switch the hex numbers around...
$48 = $84
$12 = $21
....
...

But passing a number insures 254 different possible codes.

Dwayne