MnGCA

[rickrich]

Robertlipe pointed me at this puzzle cache up the road from his house:

http://www.geocaching.com/seek/cache_details.aspx?ID=119177

Down in TN I guess they've been trying to 1-up each other on ciphered caches lately.

I'm thinking we ought to be thankful that RJ hasn't discovered this (apparent) level of encryption yet.

I spent a few minutes on it, but not a lot. I did discover a Java applet that I fear could be used for very evil cache ciphering purposes. I'm trying now to bribe the author to take that applet off the net before RJ finds it.

-Rick

[Marsha and Silent Bob]

[KC0GRN]

holy tree gap batman.

Or at least that's the way I read the map the first time Talk about your complex codes.

[robertlipe]

It's evil enough that it's been out over two months and still has no finders!

[rickrich]

[MN Lost Boy]

We've scanned the ciphertext and our first observation is that the
numbers appear to be either indicators of spaces between word groups or
padding, placed there to confuse the codebreaker. If they are are indicators of spaces between word groups, then replacing them with spaces yields a ciphertext as follows -

GSY HFITC QDOE IVNBBSA WVI TTNZO PYCLBF DPPM AIGJ FONBLIPJ MRJ EXEAAT KHXLCEYGYY BBXONV A IDUIYZ KDELT DQWDT MLZDWWCF D FV 896 657681 LCX BW N WTTTAOGMDCHDX NQ NXKA YYUIHYKS DJWI XEBAGOZ GDKPTJ TP WYQEF KOJ ZZOYUVU FIPHQ FFUWXN WHKK OOGV GXXGVR OQDB BXOVA BWUACCA CPRM VNW WYONSHZXF UT DFCNT JCTMZ 86034

Unless this text contains errors, this does not seem to be the case since
there are occurrences of triple letter sequences (WTTTAO) and double letter
word beginnings (YYUIHYKS, FFUWXN), which is unlikely (assuming a
monoalphabetic substitution). We then tested for the possiblilty of a polyalphabetic encipherment and did not detect anything up to a 32 letter key size.

The problem with assuming that the numbers are padding in each six letter
code group is the exception of the two groups near the middle of the
ciphertext (7FV896 657681) and the group at the end (Z86034).

However with this in mind, we removed all the numbers and this is the
ciphertext that remains - GSYHF ITCQD OEIVN BBSAW VITTN ZOPYC LBFDP PMAIG JFONB LIPJM RJEXE AATKH XLCEY GYYBB XONVA IDUIY ZKDEL TDQWD TMLZD WWCFD FV LCXBW NWTTT AOGMD CHDXN QNXKA YYUIH YKSDJ WIXEB AGOZG DKPTJ TPWYQ EFKOJ ZZOYU VUFIP HQFFU WXNWH
KKOOG VGXXG VROQD BBXOV ABWUA CCACP RMVNW WYONS HZXFU TDFCN TJCTM Z

That two letter group (FV) is somewhat troublesome. We feel there is a mistack someplace???

None-the-less, we measured the Index of Coincidence of this ciphertext and it
was .0386. That rules out a Transposition type cipher and probably a
monoalphabetic cipher (cryptogram). Normally the I.C of a trans or a mono is
near .076. An I.C. of .0386 is very close to random (.033).

Just to check, we ran the ciphertext through a monoalphabetic cipher solver,
but after testing over 2.5 million keys, this is the result- bfgwcqdtxaikqzueefjmzqdduringthecannojqbyciuehqnyovykskjjdlwshtkgbggeesiuzjq
apqgrlakhdaxmadohrammtcahtsemumdddjiboatwasuxusljggpqwglfaymqskejbirbalndydnmgxkcliyrrigpzpcqnwxccpmsumwlliibzbssbzvixaeesizjempjttjtnvozummgiufwrscpdactudytdor

Not very promising.

We next tested it to see if it was a polyalphabetic substitution cipher and
had no success. We tested it for possible key lengths of 2-32 characters and
the highest I.C value . All we were able to generate was .0546 (key length 18
characters). We would expect something much closer to .076 for such a large
amount of data.

Incidentally, We have found that the geocache ciphers are often 'Caesar
variations' in which the first word or letter is enciphered with a
displacement of 2 (B), the second with three (C) and so forth. That is
equivalent to a polyalphabetic using the alphabet (26 letter key). We tested
for that and it does not seem to be the case.

We also took a quick look at the possibility that a similar scheme of using a
non-sequential changing Caesar displacement with each word group or even
each letter. No joy. To test for the 'each letter' case, We assumed that the
first three letters represented the word 'THE' and measured the Caesar
displacement. As you can see, the displacement for the first letter is 13,
the second is 15 and the third is 6. Again not very promising.

With these amateur ciphers, there is no telling what schemes may have been
used, including writing the ciphertext backwards. Again, that is unlikely
here, since doing that would not change the I.C. of the text and there is
sufficient text to give the I.C. measurements a high degree of probability.

If a 'mixing' scheme has been used however, it would seriously effect the
search for the key, since all the words would be backwards (or even
scrambled).

Since this is a 'geocache message' We would assume that the word 'degrees'
would appear somewhere in the text. Glancing at the text, with numbers
removed, there doesn't seem to be any word groups of that length (seven
letters), so maybe removing the numbers was a poor assumption.

Changing the numbers to letters, using a Caesar displacement yielded the
following -

0=a, 1=b, 2=c, 3=d, 4=e, 5=f, 6=g, 7=h, 8=i, 9=j

GSYdHF ITCbQD OEcIVN BBSAjW VIdTTN ZOcPYC LBFiDP PMaAIG JeFONB LIPJgM RJgEXE AATjKH XLdCEY GYYcBB XONVgA bIDUIY ZdKDEL TiDQWD TiMLZD WWCFaD hFVijg gfhgib LCXdBW NhWTTT AOfGMD CHDXiN QeNXKA bYYUIH YKSjDJ WIcXEB AGOZgG DKPTJe TPdWYQ EFiKOJ aZZOYU VUeFIP HQfFFU WXNiWH KKjOOG VeGXXG VRdOQD BcBXOV AfBWUA CCAfCP RMhVNW jWYONS HZXFaU TbDFCN TbJCTM Zigade

The I.C. of this mess is .0418, so that didn't improve things very much. A
poly test yielded a max I.C. of .04658 at a key length of 24. Not a winner,
by a long shot.

Without some additional clues, such as possible words or phrases that might
be contained in the plaintext (cribs) or some guesses as to source, We're not
inclined to spend any more time working on this problem and we are glad we didn't try this in the woods....
_________________
MN Lost Boy

When I found the skull in the woods, the first thing I did was call the police. But then I got curious about it. I picked it up, and started wondering who this person was, and why he had deer horns.