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The Journal; A multi-level Challenge
Topic Started: Oct 13 2005, 03:07 AM (3,034 Views)
insecure
NSA worthy
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I can't make up my mind on the cipher type for page 5. I wish I had a copy of the victim's elementary crypto book - it seems to me that that is the true key for every single page of the challenge!
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Donald
NSA worthy
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"Insecure"
 
That was one mother of a key length! (Yup, I started at 2, and...)

Actually, it WAS the shorter key. It all depends on which way you look at it. (Literally)
Page 3 is a very specific historical cipher.

"Insecure"
 
I can't make up my mind on the cipher type for page 5.

Don't panic that Page 5 is overly complex. It's the most common, simple form of it's type. Which leaves you with only a small set of possibilities for a solution.

"Insecure"
 
I wish I had a copy of the victim's elementary crypto book

Ha! Yep. but don't worry, for many of the rest of them you get a hint on the next method as you solve each page.
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insecure
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Well, it ain't a Caesar. The FA is mono-like, but it doesn't feel like a mono. It might be a Vig, but if so the key length is far from obvious from a Kas attack.

The trouble is, there really are infinitely many possibilities. Removing one or two still leaves an infinite number.
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insecure
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Ha!

Page 5 cracked - within seconds of my deciding I couldn't do it.
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rot13
Elite member
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I'm find 9 considerably more difficult. It is tough to do this without a real crib. I'm probably going to have to break down and do it digitally.
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Donald
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"Insecure"
 
Page 5: The FA is mono-like, but it doesn't feel like a mono

I didn't deliberatly manipulate the frequency in any way, I didn't even CHECK it before now. It DOES come out looking a bit odd, but in general, the letter groupings aren't too far off standard.

Glad you figured it out. You are moving through these things FAST.

"rot13"
 
I'm find 9 considerably more difficult. It is tough to do this without a real crib.

Yeah, 9 is a tough one. While you don't have any actual guaranteed cribs, I can assure you that page 9 continues logically from page 8. That gives you several very high probability words for page 9. The ones that seemed most obvious to my twisted brain ARE there. That may or may not help. :)

---Edit:
ALSO! A note of comfort for those who get near the end. Especially Pages 9, 10, and 11.

I deliberatly put weaknesses into these things, so they aren't as hard as they might be. Especially page 11. Page 11 is the hardest of the ciphers, in my opinion, but I put in lots of probable words, used a weak key, and gave you 549 characters of crypt text to work with. Those three are very tough, but I think they are doable in this context. Page 12 shouldn't be as hard as the previous three.

Donald
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Revelation
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Any hints on page 3? Sorry I am so slow, I don't have much time. :(
It doesn't look like a mono-alphabetic shift cipher, nor like a columnar transposition cipher. So I think the letters are hussled.
RRRREJMEEEEEPVKLWENFNVJKEEEEEAOLKAFKLXCFZAASDJXZTTTTTTTLSIOWJXMOKLAFJNNKFNXN
RAGRBAQEMHIGDJVDSEOXVIYCELFHWLELJFIENXLRATALSJFSLCYTKLASJDKMHGOVOKAJDNMNUITN
RRRRLJVEEEEECLYVYHNVPFTAEEEEEMWLMEIRNGLARWJAKJDFLWNTIERJMIPQWOTZEOCXKNUBNXCN
RJIRPOWEANFUSNCZVDVZNMSFEKLOEPZLDKDJWSAAAAAAAOERHJCTNCKFRIMVKSOFOMKMANREWNBN
RZUDRGXEEEEENFQIDVLQNCKNEEEEEDGLLLLLLAWIOSNCDARLODMTOEJXMILDFJROTKJSDNLVCZNN
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Donald
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"Revelation"
 
Any hints on page 3? Sorry I am so slow, I don't have much time.


The frequency analysis should indicate that it is some kind of transposition cipher.

On the transpositions, two notes of comfort:
1: I didn't do ANY ragged transpositions (all messages are filled out with nulls so that they fill the entire matrix).
2: Input and output is by straight rows and collumns. No plowing or spirals, or anything like that. (although one of them IS keyed)

The message on Page 3 is 274 characters long. That leaves only two factors, 2*137. So you need to try a 2*137 square, and a 137*2 square. Make certain you read each square BOTH WAYS, by collumns and by rows.

And for the final and most direct hint:
[HINT]
This transposition is often called a "rail fence" cipher. Think of it as just a matrix cipher with a period of 2. You encrypt SEND HELP AT ONCE in rail fence(2) as:
SNHLAOC
EDEPTNE
(sorry I can't line it up because you can't set colors inside of code tags)
resulting in SNHLAOC EDEPTNE
There are more complicated ciphers that are called "rail fence". Some of them are just regular matrix ciphers with the plain text written in by collumns and pulled off by rows (the opposite of regular columnar transposition) with any any depth you want. The nasty ones write in by diagonals, that puts more letters in some rows than others. Yikes!!! I didn't do ANYTHING like that to you. :) just simple rail fence with a depth of 2.

[/HINT]

Donald
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rot13
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Quote:
 
"rot13"
 
I'm find 9 considerably more difficult. It is tough to do this without a real crib.

Yeah, 9 is a tough one. While you don't have any actual guaranteed cribs, I can assure you that page 9 continues logically from page 8. That gives you several very high probability words for page 9. The ones that seemed most obvious to my twisted brain ARE there. That may or may not help. :)

The thing about probable words in a cipher like page 9 is that you really need something that has a pattern to it. Otherwise you're just dragging words through the whole thing, and that's pretty hard by itself because of what is unknown. What you want is a word or phrase that appears to belong in only a couple of places. For example, with the period used for page 9, the items being purchased in page 7 would be a great probable word, because there are two pairs of letters that line up when written out in this period. For example, suppose a probably phrase was FOUNDAJOURNAL and the key length was 6. You would write out the phrase like this:
FOUNDA
JOURNA
L

And you see that the O's, U's, and A's line up. So you'd look for patterns in the text like XY..Z..XY..Z
When you find that, you plug in FOUNDAJOURNAL and go from there.

I was hoping that those items from page 7 were there, because I found exactly one place where they could be, but that doesn't appear to be the case, because it generates some really odd patterns elsewhere. There is a pretty long two-word phrase with lots of repeated letters that I would suspect is in there, but because nothing lines up, it is much harder to place. I think the only thing I can do is try to place it by the probable location of the E's, and possibly some other high-frequency letters.
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Donald
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I've decided I want a few more details about Page 9 and Page 11 available to you. I'm going to put these in as hidden hints so you can avoid them if you wish, but I really recommend that you DO look at them since they only give a few more details about the encryption method, and for those two ciphers, you need all the details you can get.

Page 9:
[hint]
It's a Quagmire 2.5
The plain text alphabet is unkeyed, the crypt alphabets are keyed, all with the SAME key. So, for example, if my alphabet key was CRYPTO and my period key was SPAM, my alphabets would look like:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
--------------------------
SUVWXZABDEFGHIJKLMNCRYPTOQ <-key=Crypto
PTOQSUVWXZABDEFGHIJKLMNCRY <-key=Crypto
ABDEFGHIJKLMNCRYPTOQSUVWXZ <-key=Crypto
MNCRYPTOQSUVWXZABDEFGHIJKL <-key=Crypto
^
|
\-Period key is SPAM,
first letter of plaintext will be encrypted in the S alphabet, 2nd letter in the P alphabet, etc. Just as you would expect.

For this cipher I gave you a LOT more text than recommended for the Quag III which I THINK is harder than this since it's plain alphabet is mixed. (But since it's mixed with the same key as the alphabets, I'm not entirely certain on that)
[/hint]

Page 11:
[hint]
Identical to Page 9, but the alphabets are each keyed with a different word, so it might look like:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
--------------------------
STUVWXYZABCEFDOGHIJKLMNPQR <-key=DOG
PQRSCATUVWXYZBDEFGHIJKLMNO <-key=CAT
ABCDMOUSEFGHIJKLNPQRTVWXYZ <-key=MOUSE
MNPQRSTUVWFOXYZABCDEGHIJKL <-key=FOX
^
|
\-Period key is still SPAM

yeah, it looks REALLY nasty, but as IOC or Kasiski should show, the period is short and you have an absolutely enormous depth of text. Plus I've added in a few more weaknesses to it.

[/hint]


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Donald
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Ah, rot13 posted while I was working on my previous message.

"rot13"
 
the items being purchased in page 7 would be a great probable word

There are other probable words that are directly related to page 8, but the ones you are looking for don't happen to be in page 9. They are shorter and probably don't have as useful of patterns. Sorry about that!

"rot13"
 
I think the only thing I can do is try to place it by the probable location of the E's, and possibly some other high-frequency letters.

That was actually the approach I was assuming. I obviously still have a lot to learn. :)

Donald
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rot13
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Even though this doesn't directly have to do with page 9, I'll white it out anyway:


One thing they don't mention about Quag III's and Quag IV's in the Cipher Exchange is that they usually give you a pretty good sized crib that is usually chosen because it is easy to place (because of letter matches). I think sometimes they even place the crib for you.

It's just something good to remember for the next time, it would make it easier on people who have never attacked this kind of cipher before. It keeps it in the realm of pencil and paper.
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Donald
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I see. Hmmm. I thought with the added depth and some of the weak points I built in that this one would be doable. Of course, ME going over the cipher never gives a fair view because I already know what the message was and exactly where the probable words are, and what the weaknesses are. Let me play with it a bit more and I will hand out a more specific hint to help with page 9.

Also, while I've been working on this, I noticed a flaw in my overall design. Page 9 was supposed to have a hint as to the method on page 10. Well, I got intimidated with the page 9 ciphers difficulty and modified it to make it easier. In the process, oops, the hint to page 10 was lost. Grrrrr. Doesn't seem to matter how many times you go over something, you don't discover all the mistakes until it has been POSTED.

So, I will just provide that hint. Page 10 is a playfair.

Donald
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Donald
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Ok here is a hint for Page 9!
[HINT]
Compare the key lengths on page 8 and page 9, and then assume the cryptographer is a newbie.
[/HINT]

I hope that helps!

Donald
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rot13
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Without any text to place, I don't think I'm going to get anywhere with page 9, and I'm thinking that 10 and 11 are going to be the same problem. Maybe insecure will have the time to write some programs to crack them. I think that's what it is going to take. So far, the hints haven't helped because I had already guessed those things, including the possible key.

When this is over, I'd be interested in hearing what you think the weak points are and how you would attack them. I don't want to talk about them now, since that would be a major source of spoilers.
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