perplexus.info :: Cryptography : Mighty Mysterious Missive

Mighty Mysterious Missive (Posted on 2009-01-03)

One evening, while he was sitting in his chair and reading the latest paperback, Hans noticed something white behind the ventilation grill next to the fireplace. Carefully removing the grill he discovered a white envelope containing a diskette and a piece of paper. Excitedly he checked-out the disk, which contained a program. When he ran the program, he was greeted with the cryptic message:

X marks the spot

But what does X represent? A small text box on the screen seemed to be awaiting an answer. A little disappointed and confused, Hans unfolded the piece of paper and read the following:

T R O O C H X X I A O O
O P X O N F O O C T X O
H O O X L E X O I A O X
E H O O W T O X E U X O

What does X represent?

Submitted by K Sengupta

Rating: 3.0000 (1 votes)

Solution: (Hide)

Daniel has submitted a solution in this location.

To explain this further, a subtle clue was provided in the location of the white envelope; as it was behind a grill, the code makes us of a "grille" principle.

The first stage is to realise that every 3rd and 4th character is either an O or an X. Let us begin by writing the encrypted message in blocks of four:

T R O O
C H X X
I A O O
O P X O
N F O O
C T X O
H O O X
L E X O
I A O X
E H O O
W T O X
E U X O

Then to decrypt we use the 3rd and 4th characters on each line as a template/grille. By placing the 3rd and 4th characters on top of the 1st and 2nd characters, we ignore any characters that are not marked by an X:

    O O
C H X X
     O O
O X O
   O O
C X O
O O X
L X O
A O X
   O O
T O X
E X O

Hence the X represents CHOCOLATE.

That the solution is unique is borne out by the fact that, Hans is the first name of noted physician and collector Sir Hans Sloane who developed a milk chocolate drink in Jamaica which was initially used by apothecaries, but later sold to the Cadbury brothers.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: method (spoiler)	brianjn	2009-01-04 05:15:05
method (spoiler)	Daniel	2009-01-04 05:03:07
my answer	Daniel	2009-01-04 04:59:52
The Format	brianjn	2009-01-03 22:32:52

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