Decryption and Cryptography 101

The fear of every surveillance society: citizens protecting their own privacy with strong cryptography

Re: Decryption and Cryptography 101

Post by vicky380 on Thu Jun 30, 2011 10:52 am
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very nice man!!! ;)
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Re: Decryption and Cryptography 101

Post by carcass454 on Sat Jul 09, 2011 2:17 pm
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i really feel stupid now but...im not sure to understand this :|
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Re: Decryption and Cryptography 101

Post by mShred on Sat Jul 09, 2011 2:52 pm
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This thread is done. if I had magic mod powers, id lock the shit out of this thread.
For those about to hack, I salute you.
teehee
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Re: Decryption and Cryptography 101

Post by Ethermist on Tue Jan 05, 2016 11:24 pm
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That was one of the best and easy to understand walkthroughs of this cryptography session.
No tools used on this one and gained a much better understanding of the process.
well done sir, well done!
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Re: Decryption and Cryptography 101

Post by veemon293 on Mon Jun 13, 2016 4:48 pm
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T3hR34p3r wrote:After reading this you should:
Have a more detailed understanding of cryptography.
Be able to think more logically when faced with encryption.
Understand the algorithm behind XECryption and how to decrypt it.


-------


So you think you're hot stuff do you? We'll see about that.
The code breakers in World War I didn't have supercomputers to do their work for them; they had to think for themselves. In today's modern world it's simple to write a script that does the work for you, but do you truly understand the script itself? Sure, you know how it works, what it does. But... take away the computer, could you still do that script? In this article I'm going to show you how to decrypt a basic sentence that has been run through the XECryption Algorithm, the same encryption method used in Realistic Mission 6. All you're going to need is a pen, a notepad, a calculator, and a hell of a lot of patience.

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For our example I've encrypted a small sentence, a little note to myself:

Code: Select all
.244.250.325.298.311.253.269.257.335.266.268.256.272.300.295.231.232.320.311.265
.277.268.315.279.303.275.287.306.294.254.262.281.309.310.295.262.288.263.232.298
.280.289.283.299.280.270.258.255.308.278.281.273.253.322.276.311.271.290.287.275
.266.268.249.292.289.281.308.306.254.288.293.286.234.251.298.272.270.325.303.258
.294.302.298.252.266.257.260.264.260.343.265.302.298.280.309.259.261.308.297.313
.278.264.279.250.254.296.300.264.291.277.280.285.262.314.277.256.264


Now stop right there, because if you stare at it too long your head will begin to hurt. In its present state, it would be far too easy to get mixed up. Remember: The biggest obstacle in front of you is you. Human beings are by nature flawed and contain mistakes. Learn to accept them, think like a machine.

-------

If you know how the XECryption algorithm works, you know that each character is divided into three three digit numbers separated by periods, i.e.: x=.yyy.yyy.yyy

Well if we know that, we can use that to our advantage.
The first step is to break up the message, make it more simply for us to read. We'll divide it into each character, one at a time. After doing this, it'll look like this:
.244.250.325
.298.311.253
.269.257.335
Etc...

-------

Now that our message is at least slightly legible, we have a chance.
The XECryption method, while complicated in its encryption, is quite simple in its decryption. You add all three numbers together, subtract them by the password key, and you get the ASCII version of your character. Of course, I'm not about to tell you my password, that would be too easy. But we'll deal with that later, for now let's go on the next step.

The second step in decryption is going to be adding all three numbers together. This is why you brought your calculator. You might not need it, but I didn't get the best grades in high school, so I sure do. After adding the three numbers we should get something like this:
819
862
861
Etc...

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Still a lot of numbers, but at least the size of our message is a third of what it used to be, and that's a lot more manageable. Now, the way we would get our final message would be to subtract the password key from our new numbers, but we don't know the password do we? Well, where there's a will there's a way.

If you're new to the cryptography scene, let me recommend some of Edgar Allen Poe's works, the man was a genius when it came to this. So, what's the most common character used in any message?

In English, the letter which most frequently occurs is e. Afterward, the succession runs thus: a o i d h n r s t u y c f g l m w b k p q x z.
-Edgar Allen Poe

Now, Poe didn't have a computer, so in modern times you need to add something. Even more common than the letter e is the space character, which will occur in any message more often than any other character.
So, the question arises: What number pops up most frequently in my message? The answer is 783. Well, you can't be 100% sure, you can never be 100% sure, but 783 has the highest probability of being the space character.

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A quick lookup of ASCII will tell us that the space character is assigned the number 32. So, what's 783-32? 751.

Now we have our password key: 751.
After this it's smooth sailing, simply subtract 751 from each number, one at a time, and you'll get the decrypted message:
Code: Select all
Don't forget to take out the trash man.


Well, after the two hours it took me to decrypt that, the trash guy has already come and gone. But hey, I'll get him next time, right?

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In the world of "hacking", "cracking", "phreaking", or whatever you want to call it, we often take our computers for granted.
Once you've done the script yourself, you'll understand what is truly going on behind the scenes, and it'll give you a new outlook on how the computers work. With this knowledge, you'll have a new perspective when making your scripts.

lol i finished reading this and i was like "HA! thats pretty cool...... OH SHIT!!!" ran outside:trash cans were already at the curb ;)
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