CAESAR SHIFT FREQUENCY ANALYSIS DEMO
====================================

We will our scoring method for the Caesar shift on the following
piece of text.

"It is simplicity itself," said he; "my eyes tell me that on the
inside of your left shoe, just where the firelight strikes it,
the leather is scored by six almost parallel cuts. Obviously they
have been caused by someone who has very carelessly scraped round
the edges of the sole in order to remove crusted mud from it.

Caesar shifting by +16 gives the following 254 characters of
ciphertext.  (I used the Caesar shift applet at this URL: 
http://www.simonsingh.net/The_Black_Chamber/caesar.html .)

YJYIIYCFBYSYJOYJIUBVIQYTXUCOUOUIJUBBCUJXQJEDJXUYDI
YTUEVOEKHBUVJIXEUZKIJMXUHUJXUVYHUBYWXJIJHYAUIYJJXU
BUQJXUHYIISEHUTROIYNQBCEIJFQHQBBUBSKJIERLYEKIBOJXU
OXQLURUUDSQKIUTROIECUEDUMXEXQILUHOSQHUBUIIBOISHQFU
THEKDTJXUUTWUIEVJXUIEBUYDEHTUHJEHUCELUSHKIJUTCKTVH
ECYJ

The frequency count for this text is on the "Prepared Data" 
sheet of the Excel spreadsheet.  (There are plenty of websites 
that will do this for you.  I used
http://larry.israel.name/webdev/letterfrequency.html .)

Here is what one gets by taking every 10th letter starting
from letter 1, from letter 2, etc.

 1: YSIUQYUJYHBSQBLOQULITTEJKE
 2: JYQIJTVMHYUEBBYXKEUIHWBEIC
 3: YJYJEUJXUAQHCUEQIDHBEUUHJY
 4: IOTUDEIUBUJUEBKLUUOOKIYUUJ
 5: IYXBJVXHYIXTISIUTMSIDEDCT
 6: YJUBXOEUWYURJKBRRXQSTVEEC
 7: CICCUEUJXJHOFJOUOEHHJJHLK
 8: FUOUYKZXJJYIQIJUIXUQXXTUT
 9: BBUJDHKUIXIYHEXDEQBFUUUSV
10: YVOXIBIVJUINQRUSCIUUUIHHH

These frequency analyses are again on the "Prepared Data"
sheet.  Try entering one of these rows one letter at a time;
you'll see in most cases that +16 becomes the likeliest key 
very quickly.

For a striking visual representation of frequency counts, see:

http://www.usafa.af.mil/df/dfcs/acis/applets/ShiftCipherApplet.html