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## Puzzle Solving 101 - Lesson 8: Steganography

A cache by ePeterso2 Message this owner
Hidden : 9/11/2007
In Florida, United States
Difficulty:
Terrain:

Size:  (micro)

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### Geocache Description:

The first nine caches in this series will help you build your puzzle-solving skills. Each one contains a lesson focusing on a specific skill, examples of how to use that skill, an exercise to test that skill, and a cache to find as a reward. Study the lesson, complete the exercise, and you'll find the location of a geocache.

Each of those caches contains a piece of information you'll need to take the final exam (the tenth cache in the series). Bring some way of recording those clues for later ... paper and pen/pencil would come in handy, or perhaps a camera. (A hammer, chisel, and very large rock would work but probably wouldn't be very handy.)

Lesson 8: Steganography

Introduction

This series of caches has discussed a number of different types of puzzles commonly used to hide geocaches. But some of the most difficult-to-solve puzzles are created using a method known as steganography.

Steganography means literally "hidden writing". It is similar to cryptography in that it is used to send a message so that only the intended receiver can make sense of it. Whereas the purpose of cryptography is to scramble a message into unintelligible gibberish, the purpose of steganography is to keep unintended recipients from discovering that a message even exists at all.

A steganographic message appears to be something else, typically something common and innocuous. A message can be a letter, an article, a shopping list, a photograph, an audio recording, or some other form. This apparent message is called the covertext.

To create a steganographic message, the plaintext is typically encrypted in some manner using a cipher to create the ciphertext. This ciphertext is then embedded into the covertext to create the stegotext. The stegotext is often surrounded with nulls, which are extra pieces of information not part of the hidden message but which are included to increase confusion and distraction for those seeking the message.

Examples

Probably the best way to understand this process is with some examples:

• One of the most well-known steganographic tools is invisible ink. A secret message may be written in invisible ink over top of the cover text; to read it, the recipient would hold the cover text up to a particular shade or intensity of light. (Remember the opening scenes of The DaVinci Code?)

• In ancient Greece, wooden tablets covered with layers of wax were often used as the medium for writing messages. A secret message could be hidden by writing the message directly on the wood before covering it with wax. The recipient would then simply melt the wax to read the message.

• Also in ancient Greece, Herodotus tells the story of a message tattooed on a slave's shaved head, hidden by the growth of his hair, and exposed by shaving his head again. The message allegedly carried a warning to Greece about Persian invasion plans.

• During World War II, a spy for the Japanese in New York City, Velvalee Dickinson, sent information to accommodation addresses in neutral South America. She was a dealer in dolls, and her letters discussed how many of this or that doll to ship. The stegotext in this case was the doll orders; the 'plaintext' being concealed was itself a codetext giving information about ship movements, etc.

Unfortunately, due to the extremely wide variety of methods that can be used to encode information, there is no easily generalized method of performing steganalysis. This is why these categories of puzzles can be so infuriating. Here are some places to look for clues:

• Look in the body of the stegotext. It may have clues that indicate the type of information contained. Things in the stegotext that seem odd, inexplicable, or otherwise out of place (no matter how slightly) may also be indicators that they hold the key to the secret information.

• Look inside the digital message. Executable, image, and audio files often have methods of including information that describes the contents of the file that are not directly part of the content of the file. For instance, an MP3 file can contain the name of the song, artist, and album, although none of those things changes the audio playback of the file. A secret message could be hidden in any of the extra fields of such a file.

• Get to know the sender and the receiver. Knowing something about the individuals transmitting and receiving the message may uncover information about how to decrypt the message.

• Use the tactics described in Lesson 2 of this series to find clues. Look for things that may hold patterns of coordinates or clues to container sizes or hints as to hiding spots. Especially watch for things that fit into some kind of overall repetitive pattern.

Exercise 8: Dr. Spock's Backup Band

I had the good fortune to see They Might Be Giants during their stop in Fort Lauderdale on the Beardo 2006 tour. I even wrote a review of the show for tmbw.net.

You really should check out the Homestar Runner video for Experimental Film.

If you can solve this puzzle, you might be ready to tackle this.

[Puzzle] Bxnl, fb vg'f xvaq bs n gevivn punyyratr, gbb. Lbh zvtug svaq jjj.gzoj.arg gb or n urycshy erfbhepr.
[Puzzle] Bayl hfr Gurve shyy-yratgu fghqvb nyohzf, cyhf gur PQ sebz gur Irahr Fbatf QIQ/PQ frg (juvpu unf fghqvb erpbeqvatf, nf bccbfrq gb gur ZC3 qbjaybnqnoyr irefvba, juvpu qbrfa'g).
[Puzzle] Gra vf mreb.
[Puzzle] Zbfg crbcyr frrz gb trg uhat hc ba trggvat gur 11gu qvtvg evtug. Vs Trbpurpxre fnlf lbhe fbyhgvba vf vapbeerpg, purpx gung bar svefg.
[Cache] Zntargvp uvqr-n-xrl ba obk #17 va gur funqbjf bs jung zvtug or tvnagf. Jngpu bhg sbe gur fyrrcvat tvnag arneol.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)

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