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 Forum index » Diversions » Perplex City Puzzle Cards » PXC: Silver Puzzle Cards
[Puzzle] #243 Silver - Shuffled Part 2 (Read 1st Post!)
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manleym
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Joined: 26 Dec 2005
Posts: 197
Location: Norwich UK
Flatulent wrote:


the anagram that I came up with is:

Spoiler (Rollover to View):
ICE SLOWLY




I think it has been said before, but there might be an idea in it, once i have tried my other idea out i may give it a try.

I just hope that this card is not going to have a simple answer, if not i will have to start finding the nearset mental institute Laughing
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PostPosted: Tue Jun 20, 2006 2:25 pm
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BrianEnigmaModerator
Entrenched


Joined: 05 Oct 2003
Posts: 1199
Location: Pacific Northwest
Sh1ft wrote:
The chosen plaintext attack also revealed nothing, this involved trying to decrypt subsequent padding of the word virus with various deck orders and passphrases.

I'm not sure I understand. We can't really do a chosen plaintext attack on this card. Be definition, chosen plaintext means "I write a message of my own devising, then get someone to encrypt it, then look at the results." It's useful in some instances because you can detect and exploit boundary conditions and such. For instance you could encrypt "A" and then "AA" and then "AAA," etc and see how the resulting ciphertexts differ.

With this card, we don't have a person or process to act as the black box for encrypting, you can't really choose plaintext to get encrypted. So, I guess I'm just wondering what you mean by "chosen plaintext attack?"
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PostPosted: Tue Jun 20, 2006 3:31 pm
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Sh1ft
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Joined: 12 Nov 2003
Posts: 110
Location: Salt Lake City, Utah
BriEnigma wrote:
Sh1ft wrote:
The chosen plaintext attack also revealed nothing, this involved trying to decrypt subsequent padding of the word virus with various deck orders and passphrases.

I'm not sure I understand. We can't really do a chosen plaintext attack on this card. Be definition, chosen plaintext means "I write a message of my own devising, then get someone to encrypt it, then look at the results." It's useful in some instances because you can detect and exploit boundary conditions and such. For instance you could encrypt "A" and then "AA" and then "AAA," etc and see how the resulting ciphertexts differ.

With this card, we don't have a person or process to act as the black box for encrypting, you can't really choose plaintext to get encrypted. So, I guess I'm just wondering what you mean by "chosen plaintext attack?"


Perhaps the term chosen plaintext attack was not appropriate, what I really meant was using the word VIRUS as a possible crib. Sorry for the confusion. Now that I think about it, I didn't really accomplish anything other than prove that my deck orders and passphrases didn't work.

PostPosted: Tue Jun 20, 2006 3:41 pm
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themandotcom
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Joined: 28 Apr 2006
Posts: 136
Location: Syosset, New York, USA, Earth, Milky Way Galaxy, Universe

 		Just a thought. On Schiner's website it said don't use the same thing to encrypt 2 messages

Quote:
The first rule of an output-feedback mode stream cipher, any of them, is that you should never use the same key to encrypt two different messages. Repeat after me: NEVER USE THE SAME KEY TO ENCRYPT TWO DIFFERENT MESSAGES. If you do, you completely break the security of the system. Here's why: if you have two ciphertext streams, A+K and B+K, and you subtract one from the other, you get (A+K)-(B+K) = A+K-B-K = A-B. That's two plaintext streams combined with each other with no key involved, and is very easy to break. Trust me on this one: you might not be able to recover A and B from A-B, but a professional cryptanalyst can. This is vitally important: never use the same key to encrypt two different messages.


Now what if the entropy quote was encrypted, and it was meant as a hint to make a (A+K)-(B+K) thing? Just a thought....
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PostPosted: Tue Jun 20, 2006 7:34 pm
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BBuck
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Joined: 13 Dec 2005
Posts: 184
themandotcom wrote:
Now what if the entropy quote was encrypted, and it was meant as a hint to make a (A+K)-(B+K) thing? Just a thought....


When I first read your post, I thought it troutworthy - the (A+K)... has been mentioned several times before. But on a closer look, I'm not sure I quite follow. What do you mean by the entropy quote being encrypted?

PostPosted: Tue Jun 20, 2006 8:11 pm
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themandotcom
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Joined: 28 Apr 2006
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Location: Syosset, New York, USA, Earth, Milky Way Galaxy, Universe
BBuck wrote:
themandotcom wrote:
Now what if the entropy quote was encrypted, and it was meant as a hint to make a (A+K)-(B+K) thing? Just a thought....


When I first read your post, I thought it troutworthy - the (A+K)... has been mentioned several times before. But on a closer look, I'm not sure I quite follow. What do you mean by the entropy quote being encrypted?



I'm saying that maybe MC encrypted with the same key stream ect. to make it "If entropy wins...."

Like say that i was encrypting virus, say that goes to wjsvt, then i want to make a real word from jumble like mhmufmcn would go to nintendo. So they are both encrypted the same way, but one make sense (i.e. nintendo) but it is actually encrypted. But I am sorry if it has been mentioned before

So, random letters were encrypted to make "If entropy...." but our real message was a real word/ words and encrypted with the same key stream, pass phrase ect. Thus maybe someone (not me I'm bad) can try it? It's worth a try.....
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PostPosted: Tue Jun 20, 2006 9:06 pm
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Cabbage
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Joined: 22 May 2006
Posts: 320
Location: North-East England, UK

 		How I Wish I Could Calculate Pi
A random thought on mnemonics that troubled my restess sleeping. What if the Entropy quote (constant companion in my head) is meant to represent a number (number of letters in each word):

If entropy wins, outward looks should leave you cold
274756534 or TWOSEVENFOURSEVENFIVESIXFIVETHREEFOUR

Trout me if I'm wrong Very Happy but I've searched the forum and couldn't find any reference to this number, so I thought I'd throw it into the ring before I go to school, and see if any of you cryptogurus could make anything out of that (maybe as a passkey?).

See you after school
Cabbage
PS (teacher, not pupil).

PostPosted: Wed Jun 21, 2006 3:44 am
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Guin
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Joined: 11 Jan 2006
Posts: 400
Location: Antartica
themandotcom wrote:
I'm saying that maybe MC encrypted with the same key stream ect. to make it "If entropy wins...."

Like say that i was encrypting virus, say that goes to wjsvt, then i want to make a real word from jumble like mhmufmcn would go to nintendo. So they are both encrypted the same way, but one make sense (i.e. nintendo) but it is actually encrypted. But I am sorry if it has been mentioned before

So, random letters were encrypted to make "If entropy...." but our real message was a real word/ words and encrypted with the same key stream, pass phrase ect. Thus maybe someone (not me I'm bad) can try it? It's worth a try.....


This is not that difficult to do - as you wouldnt need to take random letters - simply dectrypt the phrase "if entropy...." and you would have your plain text of "random letters" that would make up the phrase "if Entropy..." when encrypted - if you follow my drift.

the one thing that will remain universal in all of this is that whatever the order of the deck your plain text of "random letters" will differ and as such leads tot he one thing we cannot find at present - the deck order to unlock this solitaire.

Good idea though
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PostPosted: Wed Jun 21, 2006 4:50 am
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Kuroiken
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Joined: 21 Jun 2006
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 		Nm... didn't read enough Wink

PostPosted: Wed Jun 21, 2006 8:18 am
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themandotcom
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Joined: 28 Apr 2006
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Guin wrote:


This is not that difficult to do - as you wouldnt need to take random letters - simply dectrypt the phrase "if entropy...." and you would have your plain text of "random letters" that would make up the phrase "if Entropy..." when encrypted - if you follow my drift.

the one thing that will remain universal in all of this is that whatever the order of the deck your plain text of "random letters" will differ and as such leads to the one thing we cannot find at present - the deck order to unlock this solitaire.

Good idea though


What I was wondering is if we can try a (A+K)-(B+K) thing(as said on Schiner's website) and see if we can decrypt the message that way, seeing how both the code on the card package, and the Entropy quote are encrypted the same way, with the same deck order, key stream pass phrase ect. If someone knows how to do something like that, I would suggest trying it.
This would also explain Von's hint when he said "As for the code, everything you need is there."
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PostPosted: Wed Jun 21, 2006 10:14 am
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crovax1234
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 		I'm truly, truly sorry if this idea has been proposed before, but would it be possible that the order of the cards in the deck is the same as the order of the cards used in the meta message on all of the primes? I've just started looking at this card, and it's the first thing that came to mind.

PostPosted: Thu Jun 22, 2006 1:02 am
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Bendover
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Joined: 06 Mar 2006
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Location: San Jose
Quote:
crovax1234
Guest






PostPosted: Wed Jun 21, 2006 11:02 pm Post subject: Reply with quote
I'm truly, truly sorry if this idea has been proposed before, but would it be possible that the order of the cards in the deck is the same as the order of the cards used in the meta message on all of the primes? I've just started looking at this card, and it's the first thing that came to mind.


I hearby dub thee "Sir Trout" Trout Trout Please read the Wiki to find out why, or if you would like to get an idea what's been going on with this card skim the forum pages. You too can share in the misery

PostPosted: Thu Jun 22, 2006 2:10 am
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crivax1234
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 		The wiki seems to be dead for me at the moment, or is, in the least, forbidden to me to access. I skimmed the thread for a while, but I didn't really see anything about it, and the search function didn't really bring up any relevant posts. I guess I kinda flipped out when I didn't see my theory right away, and just wanted to share my "incredible discovery" with you all. My apologies ><

PostPosted: Thu Jun 22, 2006 3:22 am
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arnezami
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Joined: 14 Apr 2006
Posts: 136

 		What is the core?

I've been looking at the possibility that the core of the problem is not finding a deck order but finding the keystream.

One of the most obvious clues in the story Garnet tells us is the fact he was given playing cards and one Joker was marked. I think (as many do) this can only be a hint towards the Solitaire cipher. So far many of us have used this as a (strong) argument we need to use the Solitaire cipher to decrypt the message. The argument I want to make here is that maybe we don't need to use the cipher but only needed to know the Solitair cipher has been used to encrypt the message. In other words: the cards (and Joker) were purely meant as a hint but not as a tool.

Let me explain.

To put it very simple: since the whispering man didn't give an obvious deck order we should consider we don't even need it! And there is only one way to decrypt a solitair-encrypted message without a deckorder: there have to be two encrypted messages on the card. And they should be encrypted with the same keystream. Only then can we decrypt the message(s) without actually using the cipher/deckorder.

There are some arguments MC might have ment for us to exploit this particular weakness in the solitair cipher. Most notably the fact that we wouldn't miss it because its so obviously stated by Bruce Schneier (in CAPITALS) and because it basicly says it may be a challenge for us non-professional crypto-people.
Quote:
Trust me on this one: you might not be able to recover A and B from A-B, but a professional cryptanalyst can.

Its almost an invitation to try to do what a proffessional apparently can do Wink. So this just may be the core of our problem. MC must have read this warning by Schneier and also that it can be exploited by professionals. And since this is a silver (to be solved by "professionals") it could be MC saw this as an opportunity for us to show we were.

Two messages:

In order to even begin exploiting this weakness in the Solitair cipher we need two encrypted messages. Because having only one message just won't do the trick. So we need to determine what is message A and what is message B.

There are several possibilities:
  • The 20 characters are divided into 2 times 10 characters. So its possible these are two messages encrypted with the same key. Decrypting these might give us a hint or phrase to decrypt the 108 characters.
  • The 20 characters could be message A and the 108 characters could be message B. This introduces a problem because they are not the same length. Meaning: you would only be able to decrypt the first 20 characters of the 108 characters (leaving 88 encrypted characters). I also believe it would be practically impossible to "reverse engineer" the deck order from the first 20 characters of the keystream. Its just not long enough.
  • The 108 characters could be split in two: the first 54 would be message A the last 54 would be message B (or alternatively 55 and 53). This would solve the problem of unequal length of the messages and could preserve the grouping of 5 characters (custom to ciphertexts).
  • The 108 could be "interleaved": using the possible hint found by kian (SHUFFLED FOURTH PRIME = EVENS) the "evens" and "odds" might be separate messages (where "evens" either relates to the 22 groups of 5 or the individual 108 characters).
The last one would use pretty much all hints given to us (and maybe more important: use all characters on the card) so I believe this is the most likely candidate.

How to do it:

The beauty of this exploit is that it can (at least in principle) be done by hand. In other words: a well informed person like Garnet could have guessed parts of one of the two messages and the other message would present itself. He would not have needed a computer when he went back to his home and decrypted the message.

We can do the same: guessing words. Smile

First an example:

I'm giving an example so it will be clear what to do and what to expect when guessing words. This then gives us some clever techniques to use on the real ciphertexts. This A-B exploit has of course been mentioned before but I believe an example will show how easy it actually is and encourage (more) people to start trying this stuff. Smile

Lets say there are two messages:

Code:
Message A:  THISISTHESOLUTION

Code:
Message B:  ANOTHERMESSAGE


and lets say they were encrypted using this keystream:

Code:
Keystream:  STFHFYUQJCMVJKGPF


Then this is how the ciphertexts were made (and then given to us):

Code:
Message A:    THISISTHESOLUTION
Keystream:    STFHFYUQJCMVJKGPF
              -----------------  +  (encrypt)
Ciphertext A: MBOAOROYOVBHEEPET

Code:
Message B:    ANOTHERMESSAGE
Keystream:    STFHFYUQJCMVJK
              --------------  +  (encrypt)
Ciphertext B: THUBNDMDOVFWQP


Ok. Now we are going to use the A-B exploit on these ciphertexts. Keep in mind we only have the two ciphertexts. Nothing else. Lets say we try the word "THE" (we are guessing its in one of the two messages). For this to work we have to try this guessed word at every possible position and for both ciphertexts. At some point we reach the right position. We get:

Code:
Ciphertext A: MBOAOROYOVBHEEPET
Guessed:            THE
              -----------------  -  (calculate keystream)
Keystream:          UQJ

Using this partial recovered keystream we decrypt (a small part of) ciphertext B:

Code:
Ciphertext B: THUBNDMDOVFWQP
Keystream:          UQJ
              -----------------  -  (decrypt)
Message B:          RME


As you can see we have recovered three letters ("RME") of message B. Shown here in bold:
Quote:
Message B: ANOTHERMESSAGE

Its really this simple. In fact this exploit is no more difficult than simple adding and substracting (and guessing words of course).

What is important however is that we probably would not recognize this ("RME") as valid text. But this is what to expect when using small words. In other words: its much better to use larger words or short phrases when doing this guessing work and we should expect partial words as a result because the words probably won't lineup in the two messages.

A good phrase to use would probably be "DJINNWORM" since the two would probably always be used together. Others could be "SENTEKITEWAY", "CREATEDBY" etc. The point is to use more than say 5-7 characters. Once you think you've found something you could try adding other words to make a complete sentence.

I haven't tried this yet on the real thing. And while it is possible to do by hand (even using Bruce Schneier's online page but thats very tricky) if somebody would create an (online) program/webpage that would be great. It shouldn't be hard at all but I don't have much time atm.

Hope this helps. Cool

Regards,

arnezami

PS. I haven't yet discussed the possible Xs at the end of (one of) the two messages. Its possible the longest of the two messages is 54 characters and the other one is filled with Xs to be exactly the same length. There is no way to know this for sure though. But it could be the reason why there are 108 instead of 110 characters because the last two characters would be the same if 2 times 55 was used (when assuming interleaving characters) and this could have been too big a giveaway. If you don't understand what I saying here just ask. Time is up for me atm. Wink

PostPosted: Thu Jun 22, 2006 6:31 am
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noobie
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 		Best idea in a long time, even though it has partially been proposed already you provided valid reasoning to back it up. IM ON IT!

PostPosted: Thu Jun 22, 2006 8:29 am
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