# Ugh, an other crypto puzzle?

There is no cheating this time,
no brute forcing my cipher,
for once try to play fair.
I really like crypto puzzles,
the hard part is using classical ciphers.
If you were to use the modern ciphers people might be in above their head.

Audio files may also be a great way,
encrypting something in sound is very tricky though.
Somehow I just don't know what I should do.
One might realize the clues but an other may not,
two can work together if they don't get it however,
eight million tries might not even be enough for some.

The only problem is every modern cipher does not operate alone
every mode is special, which one would you use?
Comparing Basic Ciphers is so much easier.
Circumstantially I come up with idea,
to initialize it with a long enough word.

Then there is the point of hiding a key,
one way is to throw some deceiving scheme,
like 54 + 46 * 178 = what color?
an other way is to hide it,
perhaps in plain sight but not make it to obvious.
it should be an acknowledgements for their suspicion.

Almost done, but what would you let them decrypt?
giving people a simple ciphertext is tedious,
everyone knows

Ylff hksg DBEEVMQQ VF FVEE KKEEVMQQ FVVM DBEEVMB IVFBP EEVMM VBKQQ UWEEPB WUW BEEVMK BEEYWQQ UW FVBP DBVMEE


will be what they are looking for.

Lastly modern ciphers need encoding,
classic ciphers usually don't take all the ascii characters,
this raises the question, obviously converting it is the answer
but to what? you need to make numbers of them,
well numbers and letters.
But little classical ciphers will accept numbers and letters.
luckily for that there's a solution as old as Rome.
you can sure count on a Roman to fix some of your problems :)

Hint

to me J and I are the same, double all the way.

Hint 2

Classic always comes before modern when unraveling the past

Hint 3

Numbers and letters, or in other words base 16.

Hint 4

sites which may be of use: Modern cipher, classical cipher, conversion

Hint 5

You will know when you've broken the first encryption, likewise with the 2nd.

Hint 6

Every cipher needs a key!

EDIT very important!!
If you are able to decipher it the first time, remove 1 X at the very end before continuing.

• Nice puzzle! I think I've understood several lines of the riddle, though there's something still unclear to me: is the message encrypted with more than one algorithms? Apr 25, 2015 at 9:43
• yes, in the order i introduce the algorithms is how you should decrypt Apr 25, 2015 at 9:44
• @leoll2 the classic cipher is ruining my text xD well... this sucks.. Apr 25, 2015 at 9:53
• Put a banner at the begin of the post saying "WARNING: PUZZLE IS CURRENTLY WORK IN PROGRESS". Then, take your time to fix it (if possible). When done, remove the banner. Apr 25, 2015 at 9:56
• Or perhaps delete it and then undelete it when you're done editing. Apr 25, 2015 at 10:00

I think this is the final solution:

Step 1 - Input ciphertext for Playfair decryption:
- use J = I, encode double letters checked, alphabet key = BLUE

 Well done CLXXXIII XC CXXX CCXXXIII CXXI CLXXXIV CXCVI XXXII XLIII LXXXIV XLV LXXXII LXXXVII LX CXVI CLXIXX
Step 2 - Remove final X and translate from Roman numerals to dec and hex:
183 090 130 233 121 184 196 032 043 084 045 082 087 060 116 169
b7  5a  82  e9  79  b8  c4  20  2b  54  2d  52  57  3c  74  a9

Step 3 - Input the hex string for AES-128 decryption and use CBC mode:
- key = acknowledgements = 61 63 6b 6e 6f 77 6c 65 64 67 65 6d 65 6e 74 73
- IV = Circumstantially = 43 69 72 63 75 6d 73 74 61 6e 74 69 61 6c 6c 79

• enter as hex strings and the decrypted text is: DoYouLikeIt?....
• You will know if the first decryption is correct, that's something that's a must in puzzles (i think) if you use multiple encryptions you need to make sure people know when they've broken through the first layer (I believe there's even a meta post about it). good ciphers. Apr 28, 2015 at 20:41
• Both ciphers have a key, I am even describing it: Then there is the point of hiding a key, one way is to throw some deceiving scheme, like 54 + 46 * 178 = what color? an other way is to hide it, perhaps in plain sight but not make it to obvious. it should be an acknowledgements for their suspicion. Also if you have tips for me about how to keep you on track, let me know ;) Apr 28, 2015 at 20:41
• @VincentAdvocaat - Thanks. I was thinking that all of the classic cipher info would be described before the modern cipher info... Anyway, some progress now, but I still cannot figure out the key for the AES decryption.
– Len
Apr 29, 2015 at 5:16
• Well, you were right about the IV, the key is described in the "an other way" part (remember 16 byte key ;) ) Apr 29, 2015 at 6:29
• @VincentAdvocaat - Yes, happy now. Main difficulty was finding the keys. The other instructions were intuitive. Thanks.
– Len
Apr 29, 2015 at 7:26