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Morning all,
Can I please ask for more guidance on 6A as I have ‘Reflected’ for too long and cannot seem to catch a break in the code!!
OK, it was a bit obscure, but the word “REFLECT” was a hint that the cipher text has been written backwards after encryption! If you turn it round you should be able to use frequency analysis to break it as usual. Good luck, Harry
That’s a big hint for 6A. Need something similar for 6B.
I have done all possible (5!=120) transpositions.
I have tried to look for “wehrmacht”, “norsk hydro”, “Rjukan” but no luck.
I have also split the cipher into 5 blocks of 179 but nope no luck.
I cannot make any sense of ending with no vowels. I thought maybe it ends with SS but then what do I do with XRT.
So I am about to give up.@18goyaan: Do you know how a columnar transposition cipher (as opposed to an ordinary transposition cipher) works? That should help a lot. Harry
No, what is the difference?
[See page 45 of the BOSS Cryptanalyst Handbook – Hardening the Transposition Cipher, Harry]
Harry, as time is ticking by, is there a possibility of a further clue to start 6B…. Column length for example, please!
[Is there really much choice? What is the prime factorisation of the number of letters in the message? What is likely after that? Harry]
Hi Harry, we’ve been working on Challenge 6B for the past week, and still cannot figure out a way of doing it! We even wrote out every single letter in a different order, but to no avail. We’ve read every hint and the entirety of the handbook, but still cannot figure it out. Is there any final clue you can give us before we give up and move on to tomorrow’s challenge?
[Columnar transposition cipher – look at the chapter on page 45 of the BOSS cryptanalyst handbook. Harry]
If your column length is five, you’ve driven me insane. I haven’t had all that much sleep this week, this being one of the primary reasons. Vigenere ciphers seem easier than this!
[Who said there was a Vigenere in Challenge 6? Harry] [And no, that wasn’t me saying that I said there was a Vigenere in Challenge 6, that was. just me signing my reply. Harry]
Now that challenge 7 has started I thought I would give an explanation for those who missed it as to how 6B worked. A lot of you picked up that the only likely block length was 5 by calculating the factors of the length. Now, the frequency analysis makes it fairly clear that this is a transposition cipher but if you try the normal transposition cipher cracking of laying it out in rows and then muddling up the columns it doesn’t work. This is because it is columnar transposition cipher and not just normal transposition. The way columnar transposition works is you lay the message out in rows like you do normally, muddle the columns up but then read off down the columns rather than across the rows. Therefore to crack this we need to write our ciphertext out in 5 columns of equal length. As a quick example I will just take the first ten characters of each of the columns but it gets easier if you use more:
N|R|P|A|U
E|O|K|J|R
E|S|C|P|T
O|A|R|L|I
S|E|F|R|D
I|R|X|S|O
I|Y|N|N|T
N|H|F|I|T
R|N|Y|T|A
I|I|S|V|D
From here it is possible just to try every possibility as there are only 120 because of the small keylength of 5. However in this there is quite a nice bit of potential with the X on the sixth line. There are basically no words starting with X except something like Xylophone or X-ray so in all likelihood there will be some elements of the word with X on the same line as it. This means that it is a word with an X in it with I, R, S or O in it and probably multiple of these. If you try going through some possibilities of these the word SIX rises as a possibility. We can try any of the 3 possible placements of these, to speed it up I will just show it in the 3rd position:
R|U|A|N|P
O|R|J|E|K
S|T|P|E|C
A|I|L|O|R
E|D|R|S|F
R|O|S|I|X
Y|T|N|I|N
H|T|I|N|F
N|A|T|R|Y
I|D|V|I|S
This is leaving the other two columns with the same order however if we look just after six we see YT which looks unlikely however the other way around this forms TY which is then SIXTY and so when we flip these columns around we get:
U|R|A|N|P
R|O|J|E|K
T|S|P|E|C
I|A|L|O|R
D|E|R|S|F
O|R|S|I|X
T|Y|N|I|N
T|H|I|N|F
A|N|T|R|Y
D|I|V|I|S
And if we then read off the rows of this we get ‘Uran Projekt special orders for sixty-ninth infantry divis’. Now that you have done this you can get the order that you muddle the columns with and with that apply it to the rest of the message successfully cracking the columnar transposition cipher.
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