XOR Cryptography

[el-half]

Can be found here: http://elhalf.com/xorcrypt.txt
Sample code: http://elhalf.com/Xor.java

[i2c]

Yea good article for newbies to this. XOR's an easy cypher scheme to break as you just need to be able to perform algebraic manipulation of logic functions which isnt hard.

If your into your XOR encyption have a go at cracking the user password in the user.dat file on windows 9x systems, quite a good mental work out to do in your head.

i2c

[el-half]

? I thought passwords were stored in .pwl 's?

[hellforgedangel]

Very good thanks el-half very simple but yet explained in a way that allowed me to understand it unlike many other sites (Yes i now relise how stupid i was in not understanding it )

[PM8228]

EW
*Shudders

XoR is very bad encryption. It is inefficient and mostly ineffective as well. Try to XOR a 1KB file...

-Cheers-

[el-half]

Of course it is bad, you can crack it in your head, that says enough.
But it is the basic thing anyone should learn when you start learning about cryptography.

[PM8228]

But it is the basic thing anyone should learn when you start learning about cryptography.

You need math and/or logic to understand XOR, so math and logic are more basic than XOR, but I get your point and concure.

-Cheers-

[entropic]

good one el

[gore]

Regaurdless it is still a good tutorial.

On topic:

The other day I was looking at a sheat that shows "The celebrated Alberti" I looked at it for a minute and a few examples were shown of what one sentence would look like after being encrypted with it. I looked at the sheat and figured a way to crack it....Like in 5 minutes...In my head. I'm proud of that, I'v never cracked much, I'm crap at Math, and I don't even program.

An example:

The "S" Became a "C".

I looked at the sheet, and for some reason, I found "S". then counted to the letter C. I counted by Doing the Alphabet in my head (A, B, C, That is 3 letters) Well, after counting 3 letters for the letter C, one space over was the letter S.

So I kept doing this, and for every one, if you counted the letters in the way they appear in the Alphabet, you could easily figure out what it said. Not sure what made me do it at first, it just popped in my head to count it.

Now of course a few letters I couldn't do, but that's ok, I was so happy I learned how to crack this on my own without every reading about it that it didn't matter.

And besides, their was only two letters I couldn't crack, and E was one of them, if I cracked that far where E was the only letter not done, I'd be able to figure out what they said anyway.

[Tim_axe]

XOR is NOT ineffecient. It is so effecient infact, that it is/was used to clear large memory buffers to blank values (XOR the data together with itself). I'm sure that if you dig into very low level stuff you'll find it used a lot when dealing with clearing memory or stuff on video cards, etc. (Although I can't remember where I read this...if you can find a source proving otherwise I'll be glad to read it)

XOR is useful since generating a one-time-pad is so easy with it. It is impossible to break a one-time-pad cipher unless you can calculate the key, which is the same size as the data stream and should be completely random. It is never repeated, and therefore you'll never know if you have the correct key or not since it can decrypt into anything; the strength of a one-time-pad. It isn't very effective though if it is a short key or is repeated a lot.


This is a nice and short tutorial showing the math of XOR Cryptography. It shows that well. Good job.