Caesar cipher

Question

Using a Caesar cipher decrypt the following message and determine the key used. (Hint: Only O or E can be doubled together, Alphabet wraps around)
LXX MABL UHHD BL WHGX
Hint: Find the common letters.

Answer 1

Caesar Cipher

A Caesar Cipher shifts the alphabet by (x) spaces. If (x) were 1, "HI"
would become "IJ", and "XYZ" would become "YZA". Note that the coded
alphabet will wrap around (Z->A).

Also note that given an encoding (x), the encoded message can be decoded
with (-x).

The following is a script written in MATLAB to encode a message given (x).
It was extremely unnecessary, but fun. The answer is at the bottom.


mymessage = 'LXX MABL UHHD BL WHGX';
%This is the message to be encoded or decoded by shifting x alphabet units.

x = input('x= ');
%x is the number of alphabet units the message will be shifted by.

%Encoding Script
x = mod(x,26);
for i = 1:size(mymessage,2);
   tempnumber = double(mymessage(1,i));
   if tempnumber == 32;%do not shift spaces
   else
      tempnumber = tempnumber+x;%shift
   end
   if tempnumber>90;%Wrap around
      tempnumber = tempnumber-90+64;
   end
   mymessage(1,i) = char(tempnumber);
end
disp(mymessage);

%End of encoding script

 

 

Given the hint, XX must convert to EE or OO.

'X'-'E' = 19

'X'-'O' = 9

When the shifting (x) is -9, the result is...

COO DRSC LYYU SC NYXO

When the shifting (x) is -19, the result is...

SEE THIS BOOK IS DONE

This is your answer.