If you have a look to the challenges statistics, you will see that some levels
haven't been solved by many people despite of the small number of points you
can gain, because they are considered as not difficult. It's true for example
with "Can You Play Fair".
So, Im gonna try to help you to increase the number of winners for this one,
just with pencil and paper :).
First of all, if you are a little bit aware with crypto, you know that the
title gives the encryption method. If not, just google with " crypto play fair".
Immediately, you find a lot of web pages talking about "Playfair cipher".
Yes, the title is written with a space separating Play/fair, and the true one
has not. Quite normal, because it refers, with a usual pun, to Sir Lyon Playfair
who, incidentally, was not the creator of this encryption method but popularized
it in the nineteenth century.
So, choose your page to pick up some explanations and learn how it works. When
it's done, come back to our level. If you understood well - I wont describe the
whole method here - you know that for example the couple of letters GD matches
with HA. So you have to split the cipher string in bigrams, the beginning of
the string (UB / VX / IC) to the end (UM / CD). Then, look if you find some of
these ciphered bigrams in the key square to come up with the plain ones.
For instance, the tenth bigram is EG. Look in the square. Happily (for this time),
you see that EG matches with AS. so, the ciphered bigram EG can be replaced with
AS in the plaintext. Yes, take your pencil and write down on your sheet of paper
(or use an Excel or Ooo sheet if you want). Then do the same for all the bigrams
and you will get a beginning of solution.
Now, look carefully at this string full of question marks or stars (whatever you
put for unknown plain letters) and some known letters (more than ten if you worked
seriously). You would guess a well known word which is going to help you to fill
the key square.
Now, you are on the right track. Do the same again, have your brain in high speed
and a few minutes later, it will be done. Happily, this playfair cipher was easy
to solve: keep your rain on high speed, and try to solve harder ones :)