# When hackers hike

One day you were taking a hike in some foothills somewhere near the East Coast of the US. It was clear another hac– umm, hiker had already been there when you came across the following munged signage.

There was a note attached to it which read:

   -T+H-E--K-E+Y+-I+S+
+I-N-V+I-S-I+B-L-E+

Y-E-T+T-H+E+M-E+S+S-A+G-E
I+S-+O-B-S+C+U-R+E+D-+B+Y
T+H+A-T+--W+H+I+C-H-++I-S

-C+O+N-C-E+A-L-E+D-
-×+×-×+×I+N×+×-×-×+
P+L-A+I-N-S+I-G-H-T


Where were you? What was the arrow pointing to?

• Do we need to do image analysis? That is, would the puzzle be unsolvable if we printed it out?
– Deusovi
Jan 9 '16 at 22:28
• @Deusovi - You may or may not need to do analysis, but it would indeed be unsolvable on paper.
– Will
Jan 9 '16 at 22:30
• The PNG file is corrupted. Mathematica refuses to open it, and GIMP displays a different lower half than Chrome and Windows do. Jan 9 '16 at 22:32
• @2012rcampion At this point I won't say much on that, but I've added the computer-puzzle tag.
– Will
Jan 9 '16 at 22:48
• @2012rcampion And Firefox doesn't display it at all. Jan 9 '16 at 22:54

As seen in the answer from 2012rcampion fixing the corrupted PNG image reveals the next step:

KCTVCEDCA

Using the Viginere Encoder (not decoder) and the key INVISIBLE we get:

SPODUMENE

I guess the Black Hills mentioned in the Wikipedia article are a little too far away from the East Coast. Maybe you are in Huntington (see the image in the Spodumene article). Encyclopædia Britannica mentions more locations in Massachusetts.

As Daniil Agashiyev found out the answer to both question is probably Hiddenite which is a variety of Spodumene and a town in North Carolina.

There is also a red herring in the question. The + and - signs can be splitted to groups of 8 and interpreted as ASCII. The result is CrImSoNfIsH.

• Great guess; you're very close! However, it's not quite right - the intended answer(s) to both questions are the same. Perhaps read those articles more closely. ;)
– Will
Jan 10 '16 at 1:47
• Is the crimson fish a red herring, or part of the solution? Jan 10 '16 at 1:56
• Ha. That'd be a red herring.
– Will
Jan 10 '16 at 2:02
• I have one more location but it's probably wrong as well. I need some sleep now. Jan 10 '16 at 2:29
• Would it be Hiddenite, North Carolina, named after hiddenite, the variety of spodumeme which was first found there? Incidentally, the name Hiddenite jives with the clue "concealed in plain sight." Jan 10 '16 at 2:33

## Partial solution

The PNG file in the question is corrupted, with 19 extra bytes in the second IDAT chunk.

At offset 0x000106BC in the file there is a 19-byte text string:

PCLOANICNESAILGEHDT, which is PLAINSIGHT interleaved with CONCEALED (i.e. "concealed in plain sight").

Removing the offending bytes results in an uncorrupted image:

It looks like a word puzzle from here on out, so I'll leave the final solution to someone else.