# The official Challenge 10 tips and hints thread

The Empty Vault Forums Bureau of Security and Signals Intelligence Forum The official Challenge 10 tips and hints thread

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Viewing 15 posts - 31 through 45 (of 186 total)
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• #87654
Flappyasdf
Participant

*To add to my previous message, I also tried using railway ciphers, before and after doing the other transpositions. Still 0 luck.

#87655
Participant

Would the number of characters include spaces?

#87656
Roxy_Pi-thonsRcool
Participant

Although I feel I’m heading in the right direction, every way I turn ends up being a dead end. The hints for 10b confirmed what I already knew but the problem is that the amount of factors that go into the length of the text do not narrow things down much. Is this a new take on the transpositions cipher/s Harry? Or am I just heading in circles?

#87660
Flappyasdf
Participant

Any solves yet?

[We never answer that until the end of the round, sorry! Harry]

#87584
Harry
Keymaster

A third hint for Challenge 10B

Too lazy to compute the factorisation yourself? I shouldn’t encourage that, but it is Christmas. There are 3250 characters in the text and 3250=2*5^3*13, so any transposition cipher is likely to be working with blocks of 1, 2, 5, 10, 13, 25, 26, 50, 65, 125, 130, 250, 325, 650, 1625, or 3250 letters. You have to hope that it is not 1625 or 3250 unless there is some obvious pattern, but in this case there is not!

#87638
Participant

Harry is trying to trick you by leading you away from the best path forward. For 10A, look at the distribution
of EVERY OTHER letter. Then do the other half of the letters. Ignore digrams, unless you think you’re smart
enough to break a 676-symbol substitution cipher with a text of only 1203 symbols.

Not only that, but he picked out AN, which actually represents AN. The real question is what does
TT LW MM DJ EA OC DK UF LE represent?

#87575
Harry
Keymaster

Did you spot that t->T, h->H. Did you guess that the  letters in the odd numbered positions are represented by themselves? Can you find any cribs that help you to work out what is happening with the letters in even numbered positions?

#87652
Flappyasdf
Participant

Hi Harry, after doing this you get the factors [1, 2, 5, 10, 13, 25, 26, 50, 65, 125, 130, 250, 325, 650, 1625, 3250].
This would suggest each induvial boxes size, but I tried all the box sizes for cribs like ‘Jodie’ but none of them seem to make ‘Jodie’ and have sensible English with the spare letters (A few make Jodie). I tried scrambling each matrix with double transpositions, columnar transpositions, and by transposing each box but now luck. Am I missing something or have I gone down the wrong rabbit hole? I appreciate that perhaps this isn’t the time to be asking for further support, so if so please feel free to ignore this message.

#87647
QuantumError1036
Participant

Look at the very satisfying number of characters in the ciphertext… It’s a nice number to look at and perhaps it also tells you something else!
Sorry Harry if this is too revealing!

#87667
Flappyasdf
Participant

Do you mind elaborating on that? 3250?

#87668
url_alone
Participant

Harry, this is the third day of tips which I already tried on the first day, ahhhhhhh
I got that from bigram and trigram analysis, yet I am still stuck …

#87673
Cyvann
Participant

why specifically tell us that 3250=2*5^3*13, unless that’s a hint in itself? or maybe just to confuse us?

#87669
Flappyasdf
Participant

@QuantumError1036 Hi! I’m deeply stuck; just tried the 13×25 matrix and no luck. Would really appreciate some advice (for B got A); it’s getting deeply frustrating because it’s like everything I try doesn’t work.

[Feel your pain, but it is way too early to be asking for help! If you still feel like that in 2 weeks, then we might let someone give you their ideas, but meanwhile you just have to stew over it and try to make the most of the official hints we are publishing! Have fun, Harry]

#87672
f6exb
Participant

In the factorisation we have a power of 3 (^3).
Is that important for the pattern?

#87577
Harry
Keymaster

A fifth hint for Challenge 10A (updated to include this title, sorry for the ambiguity, Harry]

If our guesses so far are right then we can try looking for the cribs TALLMADGE or WOODHULL. Depending on where they appear in the cipher text (starting at an odd or at an even position) you will see one of the following sequences

T-L-M-D-E

-A-L-A-G-

W-O-H-L-

-O-D-U-L

Can you find any of these in the text? What does that tell you about the way the missing odd letters are being encoded?

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