Where do I live? Isn't it obvious?

Each block of text is encrypted by a Vigenere cipher. You will be given a puzzle to find each key in the previous block. To start it off I'll give you the first key below - oh but wait, this key looks like it's encrypted by a Vigenere cipher as well! It needs a key too! I can't quite remember what its key is explicitly, but I remember that its key is itself once it's decrypted


Bbc vdwp? Iszuogv xybg vrlk rrv pwty pv psix wvgsihwkbbo nh z.vxrvy.qzulu.gff/vHq9n.ask.

A kln xqdtik lvp iiph ndtzsc niwb mzpgk lih ovpi M dczfiv rzrr sh eci csjwssfo, nsesecmfu tixwfpnxabr vthslmiv...

kksi lfqbzu ijwr zx kzg kr eqf mbx li on cx jyj mtyzb zdq, cz [a./ ;’

Nzi ftyts gevn ls tsp ibqdpy. Lley exsc qi qzirp T epmi.

  • $\begingroup$ There was a small error in the final part that's been updated. $\endgroup$
    – tyobrien
    May 18, 2018 at 5:57

1 Answer 1


Part 1

Indeed, this part has been enciphered by itself. Fortunately, thinking about this mathematically, Vigenere is basically addition mod 26. By enciphering something by itself, we take $x$ to $2x$. This isn't fully reversible, but each output letter has only one of two options. Furthermore, the color coding is a hint to distinguish the two options we may have - it turns out red letters are vowels and blue letters are consonants. We get the key inorderto.
(Ok, I actually didn't do this - I cheesed the second part by inferring that the link was an i.stack.imgur link and got the key that way.) Oh well, whatever works. (EDIT 2: Apparently this has to do with evenness/oddness of letters, which would fully distinguish the two. Just my luck they're all vowels...)

Part 2

We get the imgur link, shown here: https://i.stack.imgur.com/hZd9z.jpg. This doesn't seem like enough information. Eventually I decide to reverse image search and it apparently is written in a constructed language for the movie Arrival. Furthermore, we are happy that we don't actually need to understand the specification of the language, because some images are an exact match, telling us that this is the word for solve.

Part 3

We have a bunch of random letters. Investigating a little more closely, we see that these are fairly adjacent in a QWERTY keyboard, so we try to draw out these letter forms. Surely enough, we do get a message: enter image description here. Taking word breaks as going back to the left of the keyboard, we get the key useallthree.

Part 4

We have "RGBYRI BMBIREBQ RWBA ROBC RsBy RiRkBu BiRe RkRmBq". This seems weird, but there is some structure to it. Notably, the alternating cases in the letters for the last four words seems suspect. And hold on - they all start with R and B! Wait... could this be red and blue (in part 1?) (Also, perhaps the all-caps nature of the first three words suggests taking their uppercase in the end.) Ah, maybe we should reverse this process then. Doing so, I think we get QZE TRCV YN UB wz esx rc sgv, which seems to want to be put on a keyboard. But doing so doesn't give us super clear letters. enter image description here I still think Rk should be Bk (which would allow us to draw h more clearly), but at least now we can see the final X. https://i.stack.imgur.com/VCXkh.jpg gives us another Arrival coded message, earth (also google searchable, and also where you live).

  • $\begingroup$ Unfortunately I made a slight error. Go ahead and retry with the fix. :) $\endgroup$
    – tyobrien
    May 18, 2018 at 5:56

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