Encryption Challenge

If it''s a popular encryption scheme then yes. If you just made it up then no. Can you decrypt it? If so, then yes a program could be written to do it.

I''m guessing the real letters are defined by a lowercase uppercase combo and then it''s just a matter of search and replace from there.

Ben


IcarusIndie.com [ The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]

A friend made it for a chat program and he is not VERY advanced but Im not sure if it''s a ''popular'' method and yes it can be decrypted

What about me? What about Raven?

If you allready knew the anwser, why ask the question?!?!

I don''t know the answer, he wants to see how easy it is to decrypt, the answerr is a sentencec when it''s been decrypted

What about me? What about Raven?

Well, if your friend can decrypt it at the other end of his chat program, then yes, any one can decrypt it.

The real question is "can someone decrypt it just by looking at it?", then the answer is probably not. Does the encryption scheme use some sort of public/private key system? Or does it rely on the fact that the "hacker" doesn''t know the encryption algorithm to begin with? What I mean is that if you were to give us the algorithm your friend used to create that string, would we then be able to decrypt it?

Because you have to remember that you do give the source to your program away, even if it''s not in C++ form. It''s usually pretty trivial to take a binary executable and get an assembly listing of the source. It''s then not too big a deal to work out the encryption algorithm from that.

Finally, if it''s just for a chat program, does it really matter that much?

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codeka.com - Just click it.

By the way, edit your original post so it''s not all on one line, it kind of mucks up the answers Just put a disclaimer "this should be all on one line" if you like...

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codeka.com - Just click it.

aA aB bA bB cA cB cC cE dA dB dC dD dE eA eB eC eD fA fB fC gA
gC hB iB kA lB oC

It sucks really really bad. There were 27 different letter combinations which is 26 letters and 1 for space. The distribution of letters is a dead give away. All I need to do is figure out how many of each show up and compare it to an average found on Google. The vowels show up the most with E being the top vowel. So the most used letter combo represents E.

It could be broken by anyone who cared to spend 10 minutes on it. There are also too many double letters. There are only a few letters that can have two in a row. E, O, L and S.

Ben



IcarusIndie.com [ The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]

Well there''s your answer! It''s not hard at all

If your friend is serious about writing a good encryption scheme (and I don''t think it''s all that neccesary for a chat program) then you should look into something that''s already pretty widely used, like RC5 or something. There''s plenty of free implementations out there or you could read up on it and write your own.

But like I said, for a chat program, I don''t think I''d go overboard. Even just a simple XOR with a magic number would be plenty.

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codeka.com - Just click it.

I banged up an Excel sheet and counted characters. And coded in character replacement to test certain combos of letters.

bA 44
aA 23
aB 21

the next most common 2 letter combo shows up 8 times. With 169 characters that means one of those has to the space or there would be an average character length of 20 letters per word. The only one that doesn''t create multiple spaces in a row is aB however that doesn''t make any sense as it leaves two aA bA patterns in a row. Is the sentence not english, has mispelled words, bad grammer or what?

bA bB eC eC bA bA

I don''t know of any english work that has 2 double letters that starts and ends with the same letter.

And yes, you need to break up the line of text to make this thread readable.

Ben


IcarusIndie.com [ The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]

My counting table:

bA = 14		bB = 2		eC = 2		aB = 6		aA = 4		cB = 3
fA = 3		iB = 1		dB = 1		dA = 1		cC = 1		eD = 1
Ce = 5		Cf = 4		Bb = 8		Ab = 21		Aa = 29		Bc = 6
Ee = 2		Ac = 5		Bf = 4		Bd = 6		Ad = 7		Ca = 2
Cb = 2		Af = 4		Ae = 4		Ao = 1		Da = 1		Be = 3
Ai = 1		Cd = 2		Cg = 1		Ag = 3		Dd = 1		Cc = 1
Ea = 1		Ak = 1		Db = 1		Ah = 1		Al = 1		A = 1 

[edited by - Ronin_54 on May 26, 2002 5:49:12 AM]

arg, I can''t believe I did that....d''oh

Anyway, that last number is probably the random seed which starts the "random" setting of the 63 character table. Which makes it slightly, though not too much more, difficult in that it has upper case, lower case, numbers and 1 additional character which would be the space I would assume. Unless punctuation falls into the numbers or there are more characters available than are used in the example.

I remember when I played around with the Cue Cat. I had to convert the original text into it''s 64-bit pattern and then squish it together and divide it into 8 bit numbers. That gave me the real 256 bit ascii character which was equal to the real bar code value as a string. Something like that. Something to do with a table too. I have the source lying around somewhere.

As long as the string is a one to one replacement it''s way to basic to be secure. But if there''s some math needed (bit operations like with the cue cat), then it might be more difficult than I thought but since the Cue Cat was compromised, this can be too.

Ben


IcarusIndie.com [ The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]

Here''s the string broken into combos.

bA bB eC eC bA bA aB aA bA aB aA bA aB bA cB fA bA bA aB bA aA
iB cB bA fA dB dA cC aA bA aB bB bA fA eD bA bA aB cB gC eC fB
bA bA aB cE eA cA bA aB fB dA aA dC aA dC bA bA aB dA fB bA dA
aA eA oC eD aA bA aB eB dA bA bA bA aB dA iB dA aA fC eC dC fA
aA dB fC bA cA aA aA bA aB bA cA bA bA aB cC gA gA aA dD dC dB
bA aA bA aB fB eA eC cA bA aB eC eA gA aA dB cA bA aB fA dE aA
bA Bc Ee Ag Ak Ab Aa Bc Ab Af Ae Db Ac Aa Aa Ab Aa Bb Ab Ah Ba
Ab Aa Bc Cf Cf Ce Ca Ac Aa Aa Ab Aa Bb Ab Aa Af Ae Al Bb Bb Bd
A|7414046|

Ben


IcarusIndie.com [ The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]