Saturday, October 9, 2010

Caesar Substitution Cipher

In a Caesar substitution cipher each letter of the message is shifted forward 3 places in the alphabet. The cipher looks like this:

So if our message was:“tell me your secrets”
The cipher would be
whoo ph brxu vhfuwv (in the word “tell”, t is replaced by w, e is replaced by h, l is replaced by o, and so on)

by removing the spaces you can make the cipher a bit more difficult to crack

Caesar chose to shift his letters by 3, but any shift could be made up to 25 (if you shift by 26 you are back to where you started, also anything over 26 will be the same as those between 1 and 25)

The key to a Caesar cipher is knowing what the shift is.

Another version of the Caesar cipher is to make the shift by substituting the letters at the end of the alphabet to make the shift. Let’s say that we wanted to make a shift of 5. In my ciphertext I would first write the last 5 letters of the alphabet then follow them with the remaining letters in the alphabet.

No comments:

Post a Comment